- Email: [email protected]
Constipated plasma cells associated with monomeric macroglobulinemia
Medical Intelligence CONSTIPATED PLASMA CELLS ASSOCIATED WITH MONOMERIC MACROGLOBULINEMIA M.D.,* and M.D., PH.D.t
JOHN LOUGH, JOSEPH SHUSTER,
Abstract Low molecular weight macroglobulinemia teas observed in a patient with chronic jntlmonary infectum. An enlarged cervical lymph node contained many abnormal plasma cells, which were distended with im1J~unoglobulin; this material appeared to be released mto lymph spaces when the cells burst. The macroglobulin production is considered to be a nonneopl{~stic J:eactive ,immune response to the pulmonm)' mJectlOn. It IS postulated that the association of cOJ.1Stipated plasma cells and 7s-lgM can best /;1' explained as an acquired defect in macroglobulin polymerization. The intracellular sites of synthesis of immunoglobulins in plasma cells has been ~stablished1 and electron microscopic and immunochemlcal findings in a number of plasma cell abnormalities have been described.v" However, the precise site of macroglobulin polym.erization and ~he final excretory pathway rernam to be elucidated, A patient w!th an increase in monomeric IgM associated WIth abnormal plasma cell storage of immunoglobulin has recently been observed. The observa~ions in this case are unique and may contribute to the understanding of the mechanisms of polymerization and excretion of immunoglobulin in man. CASE HISTORY A 50 year old woman was admitted to the hospital in jall1:lary 1971 for investigation of possible systermc lupus erythematosus associated with persistent pneumonia ancl cervical adenopathy. *Assisyl11t Prof'essol: of Pathology, McGill Universi ty. ASSOCiate Pathologist, Montreal General Hospital, Montreal, Quebec. tAs.sisstant Professor of Medicine, McGill University. ASSistant Physician, Department of Medicine, Montreal General Hospital, Montreal, Quebec,
Ten years earlier she had been investigated for fever of unknown origin, generalized mild lymphaden~pathy, and a palpable spleen and liver . .An .axIllary lump was found upon biopsy examination to be an infected sebaceous cyst. In Feb~'uary 1964 she developed thrornbocytopernc purpura. Two L.E. cell preparations were positive at this time. The serum proteins quantitated by paper electrophoresis scanning procedures gave values that were within normal limits: T~e sedimentation rate and chest x-ray exarmnanon were normal. She was thought to have systemic lupus erythematosus and was treated \~ith prednisone, 7.5 mg. per day, which was continued to the time of the present admission. Persistent right lower lobe pneumonia develol?ed in 1969. Tl:e skin test and complement fixatl.on. test for histoplasmosis were positive at this time. On physical examination the blood pressure was 130/80 mrn, Hg; the pulse rate was 72 per minute and regular. The chest was clear to percussion and auscultation. The heart sounds were normal. In the abdomen the tip of the spleen was palpable and the liver was felt H:'O fingerbreadths below the right costal margin. A rubbery nodule was noted in the right side of the neck. Th~ white cell co.unt wa.s 2300 per cu. mm. wah a normal differential; the red cell count was 4.9 million per cu. mm; the hematocrit. was 3?6 per cent and the erythrocyte sedimentation rate, 19 mm. per hr. A bone m.arrow aspiration showed increased cellularity w't.h . hyperact~ve granulopoiesis;. erythropOIeSIS was active and normoblastic; plasma cells and megakaryocytes were normal. Plasma cells were not increased. Serum protein electrophoresis was again normal, and no monoclonal peaks were seen. The immunoglobulin levels were IgG, 520 mg. per 100 ml. (normal, 600":' 1800); IgA, 42 mg. per 100 ml. (normal, 19-495); and IgM, 3500 mg. per m!. (normal, 57-200). The quantitative IgM elevation along with a normal scan suggested the presence of monomer IgM. This was confirmed by chromatography of her serum on Sephadex G200, which revealed t,hat the bulk of the IgM eluted at ~ole~ular weight 200 ,000. IgC antinuclear antibodies were very strongly positive by imr~lUnofiuorescence. The tanned cell agglutinanon test for rheumatoid factor was negative. The L.E. cell preparation was positive on two occasions. The blood glucose, urea, and serum
251
HUMAN PATHOLOGY - VOLUME 6, NUMBER 2
electrolyte values were normal. The old tuberculin, coccidioidomycosis, and blastomycin skin tests were negative; the histoplasmin skin test was' positive. In the chest x-ray view there were increased numbers of conglomerate nodules in the right lower lobe. An excision biopsy was done on the cervicallymph node and the presence of abnormal plasma cells was noted. She was considered to have collagen vascular disease and was treated with prednisone, 4 mg. three times daily. One year later she was readmitted because of right lower lobe pneumonia, which had never completely cleared. The chest x-ray film was interpreted as showing' right lower lobe consolidation with abscess cavities. The serum protein electrophoresis and immunoglobulin profiles were similar to those of the previous admission. A right middle and lower lobectomy was performed. Postoperatively the patient continued to have severe respiratory distress and ultimatel y died of bronchopneumonia and empyema. The cervical lymph node removed in 1971 was fragmented but appeared to be enclosed by a capsule. The usual follicle structure was completely effaced, and there was no distinction between the cortex and medulla. The predominant types of cells were lymphocytes, plasma cells, and large plump cells distended
252
Figure 1. Light microscopic picture of enlarged cervical lymph node. The follicular architecture is effaced. Plump PAS positive plasma cells with a bubbly cytoplasm are prominent. Lymphocytes, mononuclear leukocytes, and normal plasma cells are also seen. (X 400.)
Murclt /975
with eosinophilic droplets and having a small round dark nucleus (Fig. I). Reticulum cells were present in small numbers. With the periodic acid-Schiff (PAS) stain the plump cells were seen to contain PAS positive material, which was diastase resistant and unstained with alcian blue. These cells were also pyronin positive, indicating that they were of plasma cell origin, and distended with neutral mucopolysaccharide. Extravasated PAS positive material, sometimes still in droplets, was frequently seen between cells and within lymph spaces. Small pieces of lymph node were fixed in glutaraldehyde, postfixed in osmium, embedded in Epon, and stained with lead citrate and osmium tetroxide for electron microscopy. The abnormal plasma cells were found to contain moderately osmiophilic amorphous material within distended cisternae of rough endoplasmic reticulum (Figs. 2, 3). In the less severely affected cells the material appeared initially to accumulate centrally with retention of normallarnellar rough reticulum peripherally. The Golgi area often appeared dist.ended and empty. Occasionally, small smooth surfaced vesicles containing dense osmiophilic material were present in the Golgi area of the abnormal cells. In the more severely affected cells there was a globular distention of the entire rough reticulum (Fig. 4). In some cells there was irregular disruption of the rough reticulum and of the plasma membrane with release of cytoplasmic constituents into lymph spaces. The amorphous material in the rough reticulum was morphologically similar to t.hat seen in the lymph spaces. In the resected lower lobe of lung there was a lobulated pale yellow mass, which measured 10 em. in greatest dimension. There were a few irregular areas of necrosis centrally surrounded by yellow fleshy consolidation. The remainder of the lung was atelectatic. The hilar lymph nodes remained discrete. Microscopically the mass was centrally necrotic and lung parenchyma was destroyed. At the margins it was subdivided by lobular septae in which the alveoli were distended by lipid laden histiocytes and fibrin with a peripheral rim of lymphocytes. Many thrombosed vessels were evident. In the most cellular areas there was a polymorphous infiltrate composed of histiocytes. Mononuclear giant cells with large irregular hyperchromatic nuclei, plasma cells, and lymphocytes were more frequently seen peripherally. The smaller nodules seemed to be oriented around bronchi containing polymorphonuclear leukocytes with atypical monocytes present in small numbers in the submucosa. The adjacent artery was not involved in the early lesion.
MEDICAL INTELLIGENCE
Figure 2. Abnormal plasma cells in which immunoglobulin is seen to distend the rough reticulum, beginning centrally adjacent to the Golgi area (G). The lymph sapces (L) between are inconspicuous. (Uranyl acetate and lead citrate stain. X II,fJOO.)
Figure 3. In more severely affected cells the endoplasmic reticulum is distended up to the periphery and is sometimes discontinuous around the immunoglobulin droplets. Lymph spaces (1,) are prominent. P. normal plasma cell. (Uranyl acetate and lead citrate stain. X 11.000.)
253
HUMAN PATHOLOGY - VOLUME 6, NUMBER 2
March /975
~\
.
Figure 4. Two constipated plasma cells in which there is cytoplasmic disorganization with disruption of rough reticulum about the globules. (Uranyl acetate and lead citrate stain. X 11,000.)
In the hilar lymph nodes there was a sinus hyperplasia. Pyronin positive plasma cells were plentiful in these nodes and some were distended with PAS positive material as in the cervical node biopsy specimen. The diagnosis was chronic pneumonitis of the cholesterol type. At postmortem examination there was extensive pneumonia; the hilar lymph nodes were enlarged, with prominent sinuses but poorly developed follicles. Atypical mononuclear cells were present, but there was no lymph node destruction or consolidation as seen in the resected lung. No morphological evidence of lupus erythematosus was found in the spleen, heart, or kidneys. The bone marrow was hypercellular but did not contain tumor or increased numbers of plasma cells. COMMENT
254
This unusual case was characterized by the presence of systemic lupus erythematosus associated with the development of chronic pneumonitis. A reactive cervical lymph node contained abnormal plasma cell inclusions, and there was an associated circulating monomeric IgM. Low molecular weight macroglobulin (7s-IgM) has been described in a variety of
disorders, including lupus erythematosus, ataxia telangiectasia, antibody deficiency syndromes, malignant disease of the plasma cell series, and some cases of cirrhosis." 7s-IgM, which is present in approximately 15 per cent of the patients with systemic lupus erythematosus,' has been shown to have antinuclear and incomplete isoagglutinin activity." Immunochemical studies have shown that 7s-IgM is similar to Be in both sedimentation properties and elution pattern from gel filtration, and is therefore about the same size.": 10 19s-IgM has a molecular weight of about 890,000 and is normally present in the serum as a covalently assembled pentamer of the basic four chain structure. Polymerization takes place immediately before the secretion of 19s-IgM, since radioactive labeling studies in vitro showed that only the monomer 7s-IgM could be detected inside the cell and only the pentamer 19s-IgM outside." It is likely that a microsomal enzyme is required for superassernbly.P Earlier studies have shown that 7s-IgM does not originate from catabolism of 19s-IgM so that it must be a precursor of 19s-IgM, Or it may be synthesized indepenrlently.!" as it is in the dogfish but not normally in man. It has been shown that the polypeptide
MEDICAL INTELLIGENCE backbone of the immunoglobulin molecule is synthesized in the rough endoplasmic reticulurn.' The carbohydrate moieties glucosamine and galactose are attached in the rough endoplasmic reticulum and Golgi area. Immunoglobulin is therefore a mucopolysaccharide or glycoli pid and corresponds with the periodic acid-Schiff positive material seen in light microscopy." The abnormal plasma cells in this case were shown to accumulate immunoglobulin within the rough endoplasmic reticulum. In the least affected, onlv the central cisternae adjacent to the Golgi area were dilated whereas in the most severely affected, the entire rough reticulum was tremendously distended by the accumulated protein. Many ruptured cells were also present, and it is likely that the secretory products find their way into the intercellular spaces and vascular channels after the distended cells burst. The association of abnormal plasma cells and the 7s-IgM immunoglobulin can be best explained as an acquired failure of' polymerization of the monomeric IgM to the pentamer. Since the molecule is not completed, it does not follow the normal excretory transport process from the Golgi area to the plasma membrane but instead accumulates in the rough reticulum and is released only when the cell ruptures. It then reaches the circulation where it can be detected as monomer IgM. This hypothesis is supported by the apparent dilation of the Golgi area in the abnormal cells and the paucity of dense material in smooth vesicles in the Golgi area as seen in normal cells, since it is believed that the completed Ig;M is transported to the plasma membrane within smooth vesicles and released by reverse pinocytosis. It is noteworthy that there were some smooth vesicles containing dense material in the abnormal cells, suggesting that the secretory block is incomplete or that it may be selective and that other molecules synthesized by the plasma cells can be secreted in the normal way. A prominent and sometimes vacuolated Golgi apparatus and a progressively distended rough reticulum are characteristic of stimulated plasma cells and myeloma," but have never been demonstrated to this degree, terminating with rupture and release of immunoglobulin, The ultrastructure of these cells is distinct from that previously described in cases of' macroglobulinemia," myeloma," and heavy chain disease." They do resemble the reactive plasma cells seen around a gastric
ulcer." The association of the constipated plasma cells and the 7s-IgM in this case suggests an acquired defect in macroglobulin polymerization.
Acknowledgment Electron microscopic and photographic technical procedures were done by Patricia Spicer. References I. Zagury, D.. Uhr,,]. W.,Jamieson,,]. D.. and Palade, G. E.:
Immunoglobulin synthesis and secretion. H. Radioautographic studies of sites of addition of carbohydrate moieties and intracellular transport. J. Cell BioI.. 0/6:52. 1970. 2. Zolla, S.• Buxbaum. .I., Franklin, E. C .• and Scharff. M. D.: Synthesis and assembly of immunoglobulins by malignant. human plasmacyres. J. Exp. Med.. 132: 148. 1970. 3. Maldonada, J. E" Brown, A. L., ./r .. Bayrd, E. D .• and Pease, G. L.: Ultrastructure of the myeloma cell. Cancer, 19: ll;I;\, H16li, 4. Wanebo, H . .I.. and Clarkson, B. D.: Essential macroglobulinemia. Report of a case including immunofluorescent and E. M. studies, Ann. Int. Med.. 62: 1025. 1965. 5. Zucker-Franklin, D., and Franklin, E. C.: Ultrastrucrural and immunofluorescence studies of the cells associated with JL chain disease. Blood, 37:257, 1971. li. Bush, S. T., Swedlund. H, A., and Gleich, G . .I.: Low molecular weight IgM in human sera. ./. Lab. Clin. Med., 73: 194. 1%9. 7. Stobo, J. D., and Tomasi. T. B" .Jr.: A low molecular weight immunoglobulin antigenically related to 19s-IgM. .I. Clin. Lnvest., "/6: 1329, 1967. 8. Rothfield, N. F.. Frangione, B.. and Franklin, E. C.: Slowly sedimenting mcrcapto-ethanol-rcsistant antiIllI..'Jl'ar f;u."tors related antigenicallv to 1\-1 i m munoglubulins (6 I.M-globulin) in patients with S,L.E, i. elin. l nvest., -1-1:62, /965. 9, Miller, F.. and Metzger. H.: Characterization ofa human macroglobulln.J. The molecular weight of its subunit. .I. BioI. Chern" 240::3:325, I f1tl5, 10. Swedlund. H. A.. Gleich. G,.J .. and Chodirker, W, n,: Comparison of certain properties of naturally occur, ring low molecular weight B M and the 1) M monomer derived by reduction and alkylation of 19sBM. J. Immun .. 100:1296.1968. II. Parkhouse, R. M. E .• and Askonas, B. A.: Immunoglobulin M biosynthesis, Intracellular accumulation of 7s subunits. Biochem. .J.• I};: 163, I9li9. 12. Williamson. A. R.: Biosynthesis of antibodies. Nature. 231::l59.I971. 13. Grigg's, R. C .. Strobe r, W., and Mcf'a rliu , D. E.: Recurrent encephalopathy associated with low molecular weight 1) M in the serum and cerebrospinal fluid. Arch. Neurol., 21:30;\, 19tH), 14. Welsh, R. A,: Light and electron microscopic correlation of the P.A.S. reaction ill the human plasma cell. AnI. J. Path., 40:285. 1965. 15. Bosman, C.• Fcldman,J. D" and Pick. E.: Heterogeneity of antibody-forming cells. An E.M. analysis. J. Exp. Med., 129:1029. 1969.
255
JOHN LOUGH, JOSEPH SHUSTER,
Abstract Low molecular weight macroglobulinemia teas observed in a patient with chronic jntlmonary infectum. An enlarged cervical lymph node contained many abnormal plasma cells, which were distended with im1J~unoglobulin; this material appeared to be released mto lymph spaces when the cells burst. The macroglobulin production is considered to be a nonneopl{~stic J:eactive ,immune response to the pulmonm)' mJectlOn. It IS postulated that the association of cOJ.1Stipated plasma cells and 7s-lgM can best /;1' explained as an acquired defect in macroglobulin polymerization. The intracellular sites of synthesis of immunoglobulins in plasma cells has been ~stablished1 and electron microscopic and immunochemlcal findings in a number of plasma cell abnormalities have been described.v" However, the precise site of macroglobulin polym.erization and ~he final excretory pathway rernam to be elucidated, A patient w!th an increase in monomeric IgM associated WIth abnormal plasma cell storage of immunoglobulin has recently been observed. The observa~ions in this case are unique and may contribute to the understanding of the mechanisms of polymerization and excretion of immunoglobulin in man. CASE HISTORY A 50 year old woman was admitted to the hospital in jall1:lary 1971 for investigation of possible systermc lupus erythematosus associated with persistent pneumonia ancl cervical adenopathy. *Assisyl11t Prof'essol: of Pathology, McGill Universi ty. ASSOCiate Pathologist, Montreal General Hospital, Montreal, Quebec. tAs.sisstant Professor of Medicine, McGill University. ASSistant Physician, Department of Medicine, Montreal General Hospital, Montreal, Quebec,
Ten years earlier she had been investigated for fever of unknown origin, generalized mild lymphaden~pathy, and a palpable spleen and liver . .An .axIllary lump was found upon biopsy examination to be an infected sebaceous cyst. In Feb~'uary 1964 she developed thrornbocytopernc purpura. Two L.E. cell preparations were positive at this time. The serum proteins quantitated by paper electrophoresis scanning procedures gave values that were within normal limits: T~e sedimentation rate and chest x-ray exarmnanon were normal. She was thought to have systemic lupus erythematosus and was treated \~ith prednisone, 7.5 mg. per day, which was continued to the time of the present admission. Persistent right lower lobe pneumonia develol?ed in 1969. Tl:e skin test and complement fixatl.on. test for histoplasmosis were positive at this time. On physical examination the blood pressure was 130/80 mrn, Hg; the pulse rate was 72 per minute and regular. The chest was clear to percussion and auscultation. The heart sounds were normal. In the abdomen the tip of the spleen was palpable and the liver was felt H:'O fingerbreadths below the right costal margin. A rubbery nodule was noted in the right side of the neck. Th~ white cell co.unt wa.s 2300 per cu. mm. wah a normal differential; the red cell count was 4.9 million per cu. mm; the hematocrit. was 3?6 per cent and the erythrocyte sedimentation rate, 19 mm. per hr. A bone m.arrow aspiration showed increased cellularity w't.h . hyperact~ve granulopoiesis;. erythropOIeSIS was active and normoblastic; plasma cells and megakaryocytes were normal. Plasma cells were not increased. Serum protein electrophoresis was again normal, and no monoclonal peaks were seen. The immunoglobulin levels were IgG, 520 mg. per 100 ml. (normal, 600":' 1800); IgA, 42 mg. per 100 ml. (normal, 19-495); and IgM, 3500 mg. per m!. (normal, 57-200). The quantitative IgM elevation along with a normal scan suggested the presence of monomer IgM. This was confirmed by chromatography of her serum on Sephadex G200, which revealed t,hat the bulk of the IgM eluted at ~ole~ular weight 200 ,000. IgC antinuclear antibodies were very strongly positive by imr~lUnofiuorescence. The tanned cell agglutinanon test for rheumatoid factor was negative. The L.E. cell preparation was positive on two occasions. The blood glucose, urea, and serum
251
HUMAN PATHOLOGY - VOLUME 6, NUMBER 2
electrolyte values were normal. The old tuberculin, coccidioidomycosis, and blastomycin skin tests were negative; the histoplasmin skin test was' positive. In the chest x-ray view there were increased numbers of conglomerate nodules in the right lower lobe. An excision biopsy was done on the cervicallymph node and the presence of abnormal plasma cells was noted. She was considered to have collagen vascular disease and was treated with prednisone, 4 mg. three times daily. One year later she was readmitted because of right lower lobe pneumonia, which had never completely cleared. The chest x-ray film was interpreted as showing' right lower lobe consolidation with abscess cavities. The serum protein electrophoresis and immunoglobulin profiles were similar to those of the previous admission. A right middle and lower lobectomy was performed. Postoperatively the patient continued to have severe respiratory distress and ultimatel y died of bronchopneumonia and empyema. The cervical lymph node removed in 1971 was fragmented but appeared to be enclosed by a capsule. The usual follicle structure was completely effaced, and there was no distinction between the cortex and medulla. The predominant types of cells were lymphocytes, plasma cells, and large plump cells distended
252
Figure 1. Light microscopic picture of enlarged cervical lymph node. The follicular architecture is effaced. Plump PAS positive plasma cells with a bubbly cytoplasm are prominent. Lymphocytes, mononuclear leukocytes, and normal plasma cells are also seen. (X 400.)
Murclt /975
with eosinophilic droplets and having a small round dark nucleus (Fig. I). Reticulum cells were present in small numbers. With the periodic acid-Schiff (PAS) stain the plump cells were seen to contain PAS positive material, which was diastase resistant and unstained with alcian blue. These cells were also pyronin positive, indicating that they were of plasma cell origin, and distended with neutral mucopolysaccharide. Extravasated PAS positive material, sometimes still in droplets, was frequently seen between cells and within lymph spaces. Small pieces of lymph node were fixed in glutaraldehyde, postfixed in osmium, embedded in Epon, and stained with lead citrate and osmium tetroxide for electron microscopy. The abnormal plasma cells were found to contain moderately osmiophilic amorphous material within distended cisternae of rough endoplasmic reticulum (Figs. 2, 3). In the less severely affected cells the material appeared initially to accumulate centrally with retention of normallarnellar rough reticulum peripherally. The Golgi area often appeared dist.ended and empty. Occasionally, small smooth surfaced vesicles containing dense osmiophilic material were present in the Golgi area of the abnormal cells. In the more severely affected cells there was a globular distention of the entire rough reticulum (Fig. 4). In some cells there was irregular disruption of the rough reticulum and of the plasma membrane with release of cytoplasmic constituents into lymph spaces. The amorphous material in the rough reticulum was morphologically similar to t.hat seen in the lymph spaces. In the resected lower lobe of lung there was a lobulated pale yellow mass, which measured 10 em. in greatest dimension. There were a few irregular areas of necrosis centrally surrounded by yellow fleshy consolidation. The remainder of the lung was atelectatic. The hilar lymph nodes remained discrete. Microscopically the mass was centrally necrotic and lung parenchyma was destroyed. At the margins it was subdivided by lobular septae in which the alveoli were distended by lipid laden histiocytes and fibrin with a peripheral rim of lymphocytes. Many thrombosed vessels were evident. In the most cellular areas there was a polymorphous infiltrate composed of histiocytes. Mononuclear giant cells with large irregular hyperchromatic nuclei, plasma cells, and lymphocytes were more frequently seen peripherally. The smaller nodules seemed to be oriented around bronchi containing polymorphonuclear leukocytes with atypical monocytes present in small numbers in the submucosa. The adjacent artery was not involved in the early lesion.
MEDICAL INTELLIGENCE
Figure 2. Abnormal plasma cells in which immunoglobulin is seen to distend the rough reticulum, beginning centrally adjacent to the Golgi area (G). The lymph sapces (L) between are inconspicuous. (Uranyl acetate and lead citrate stain. X II,fJOO.)
Figure 3. In more severely affected cells the endoplasmic reticulum is distended up to the periphery and is sometimes discontinuous around the immunoglobulin droplets. Lymph spaces (1,) are prominent. P. normal plasma cell. (Uranyl acetate and lead citrate stain. X 11.000.)
253
HUMAN PATHOLOGY - VOLUME 6, NUMBER 2
March /975
~\
.
Figure 4. Two constipated plasma cells in which there is cytoplasmic disorganization with disruption of rough reticulum about the globules. (Uranyl acetate and lead citrate stain. X 11,000.)
In the hilar lymph nodes there was a sinus hyperplasia. Pyronin positive plasma cells were plentiful in these nodes and some were distended with PAS positive material as in the cervical node biopsy specimen. The diagnosis was chronic pneumonitis of the cholesterol type. At postmortem examination there was extensive pneumonia; the hilar lymph nodes were enlarged, with prominent sinuses but poorly developed follicles. Atypical mononuclear cells were present, but there was no lymph node destruction or consolidation as seen in the resected lung. No morphological evidence of lupus erythematosus was found in the spleen, heart, or kidneys. The bone marrow was hypercellular but did not contain tumor or increased numbers of plasma cells. COMMENT
254
This unusual case was characterized by the presence of systemic lupus erythematosus associated with the development of chronic pneumonitis. A reactive cervical lymph node contained abnormal plasma cell inclusions, and there was an associated circulating monomeric IgM. Low molecular weight macroglobulin (7s-IgM) has been described in a variety of
disorders, including lupus erythematosus, ataxia telangiectasia, antibody deficiency syndromes, malignant disease of the plasma cell series, and some cases of cirrhosis." 7s-IgM, which is present in approximately 15 per cent of the patients with systemic lupus erythematosus,' has been shown to have antinuclear and incomplete isoagglutinin activity." Immunochemical studies have shown that 7s-IgM is similar to Be in both sedimentation properties and elution pattern from gel filtration, and is therefore about the same size.": 10 19s-IgM has a molecular weight of about 890,000 and is normally present in the serum as a covalently assembled pentamer of the basic four chain structure. Polymerization takes place immediately before the secretion of 19s-IgM, since radioactive labeling studies in vitro showed that only the monomer 7s-IgM could be detected inside the cell and only the pentamer 19s-IgM outside." It is likely that a microsomal enzyme is required for superassernbly.P Earlier studies have shown that 7s-IgM does not originate from catabolism of 19s-IgM so that it must be a precursor of 19s-IgM, Or it may be synthesized indepenrlently.!" as it is in the dogfish but not normally in man. It has been shown that the polypeptide
MEDICAL INTELLIGENCE backbone of the immunoglobulin molecule is synthesized in the rough endoplasmic reticulurn.' The carbohydrate moieties glucosamine and galactose are attached in the rough endoplasmic reticulum and Golgi area. Immunoglobulin is therefore a mucopolysaccharide or glycoli pid and corresponds with the periodic acid-Schiff positive material seen in light microscopy." The abnormal plasma cells in this case were shown to accumulate immunoglobulin within the rough endoplasmic reticulum. In the least affected, onlv the central cisternae adjacent to the Golgi area were dilated whereas in the most severely affected, the entire rough reticulum was tremendously distended by the accumulated protein. Many ruptured cells were also present, and it is likely that the secretory products find their way into the intercellular spaces and vascular channels after the distended cells burst. The association of abnormal plasma cells and the 7s-IgM immunoglobulin can be best explained as an acquired failure of' polymerization of the monomeric IgM to the pentamer. Since the molecule is not completed, it does not follow the normal excretory transport process from the Golgi area to the plasma membrane but instead accumulates in the rough reticulum and is released only when the cell ruptures. It then reaches the circulation where it can be detected as monomer IgM. This hypothesis is supported by the apparent dilation of the Golgi area in the abnormal cells and the paucity of dense material in smooth vesicles in the Golgi area as seen in normal cells, since it is believed that the completed Ig;M is transported to the plasma membrane within smooth vesicles and released by reverse pinocytosis. It is noteworthy that there were some smooth vesicles containing dense material in the abnormal cells, suggesting that the secretory block is incomplete or that it may be selective and that other molecules synthesized by the plasma cells can be secreted in the normal way. A prominent and sometimes vacuolated Golgi apparatus and a progressively distended rough reticulum are characteristic of stimulated plasma cells and myeloma," but have never been demonstrated to this degree, terminating with rupture and release of immunoglobulin, The ultrastructure of these cells is distinct from that previously described in cases of' macroglobulinemia," myeloma," and heavy chain disease." They do resemble the reactive plasma cells seen around a gastric
ulcer." The association of the constipated plasma cells and the 7s-IgM in this case suggests an acquired defect in macroglobulin polymerization.
Acknowledgment Electron microscopic and photographic technical procedures were done by Patricia Spicer. References I. Zagury, D.. Uhr,,]. W.,Jamieson,,]. D.. and Palade, G. E.:
Immunoglobulin synthesis and secretion. H. Radioautographic studies of sites of addition of carbohydrate moieties and intracellular transport. J. Cell BioI.. 0/6:52. 1970. 2. Zolla, S.• Buxbaum. .I., Franklin, E. C .• and Scharff. M. D.: Synthesis and assembly of immunoglobulins by malignant. human plasmacyres. J. Exp. Med.. 132: 148. 1970. 3. Maldonada, J. E" Brown, A. L., ./r .. Bayrd, E. D .• and Pease, G. L.: Ultrastructure of the myeloma cell. Cancer, 19: ll;I;\, H16li, 4. Wanebo, H . .I.. and Clarkson, B. D.: Essential macroglobulinemia. Report of a case including immunofluorescent and E. M. studies, Ann. Int. Med.. 62: 1025. 1965. 5. Zucker-Franklin, D., and Franklin, E. C.: Ultrastrucrural and immunofluorescence studies of the cells associated with JL chain disease. Blood, 37:257, 1971. li. Bush, S. T., Swedlund. H, A., and Gleich, G . .I.: Low molecular weight IgM in human sera. ./. Lab. Clin. Med., 73: 194. 1%9. 7. Stobo, J. D., and Tomasi. T. B" .Jr.: A low molecular weight immunoglobulin antigenically related to 19s-IgM. .I. Clin. Lnvest., "/6: 1329, 1967. 8. Rothfield, N. F.. Frangione, B.. and Franklin, E. C.: Slowly sedimenting mcrcapto-ethanol-rcsistant antiIllI..'Jl'ar f;u."tors related antigenicallv to 1\-1 i m munoglubulins (6 I.M-globulin) in patients with S,L.E, i. elin. l nvest., -1-1:62, /965. 9, Miller, F.. and Metzger. H.: Characterization ofa human macroglobulln.J. The molecular weight of its subunit. .I. BioI. Chern" 240::3:325, I f1tl5, 10. Swedlund. H. A.. Gleich. G,.J .. and Chodirker, W, n,: Comparison of certain properties of naturally occur, ring low molecular weight B M and the 1) M monomer derived by reduction and alkylation of 19sBM. J. Immun .. 100:1296.1968. II. Parkhouse, R. M. E .• and Askonas, B. A.: Immunoglobulin M biosynthesis, Intracellular accumulation of 7s subunits. Biochem. .J.• I};: 163, I9li9. 12. Williamson. A. R.: Biosynthesis of antibodies. Nature. 231::l59.I971. 13. Grigg's, R. C .. Strobe r, W., and Mcf'a rliu , D. E.: Recurrent encephalopathy associated with low molecular weight 1) M in the serum and cerebrospinal fluid. Arch. Neurol., 21:30;\, 19tH), 14. Welsh, R. A,: Light and electron microscopic correlation of the P.A.S. reaction ill the human plasma cell. AnI. J. Path., 40:285. 1965. 15. Bosman, C.• Fcldman,J. D" and Pick. E.: Heterogeneity of antibody-forming cells. An E.M. analysis. J. Exp. Med., 129:1029. 1969.
255