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The formation of macrophages from lymphocytes in vitro
476
Experimental
THE
FORMATION
OF MACROPHAGES
LYMPHOCYTES J. GOUGH, Department
Haematology, Manchester,
FROM
IN VITRO
M. W. ELVES
of Clinical
Cell Research 38, 476-482 (IDC5)
and M. C. G. ISRAeLS University England
and Royal Injirmary,
Received September 4, 1964
THE transformation of lymphocytes into “blast”-like cells under the influence of phytohaemagglutinin (PHA) [7, 8, 9, 141 and various antigens [lo, 19, 221 is well established. The formation of macrophages in hangingdrop cultures of leucocytes has been known for many years [ 1, 6, 11, 15 ], but comparatively little attention has been paid in recent years to the development of such cells when fluid culture media are used. The present investigations were performed to assess the degree of macrophage formation in vitro and to determine the origin of these cells. The recognition of macrophages in leucocyte cultures is considered to be important in view of the fact that some of the cells bear superficial resemblances to the “blast”-like cells of PHA and antigen cultures.
MATERIALS
AND
METHODS
Leucocyte cultures were prepared using normal human blood by the method of Hungerford et al. [13] except that PHA was not added. In each experiment four sets of cultures were made. Carbon particles in the form of Indian ink were added to each culture of the first set, and similarly very fine silica particles were added to the second set. In the third set carbon was added 2 hr before the cultures were sacrificed, while the fourth set was untreated and acted as a control. Cultures were incubated at 37°C and sacrificed at various intervals from 0 to 72 hr. The experiments were repeated on five occasions using different leucocyte donors. Smears of the centrifuged cellular deposits were made and stained by Jenner-Giemsa stain. In order to investigate the relationship between the lymphocytes and the polymorphs in these cultures the following additional experiment was performed. Pure lymphocyte cultures were obtained by separating the lymphocytes from the other cells by incubation of the cell/plasma suspension on cotton wool columns at 37°C for l-2 hr and eluting the viable lymphocytes with culture medium. Some of these cultures were left untreated whilst polymorphs were added to others. To determine the necessity for living polymorphs, heat-killed polymorphs were added to other pure lymphocyte cultures. Cultures were then examined in the usual way. Experimental
Cell Research 38
Formation
of macrophages from lymphocytes
in vitro
177
In order to demonstrate the origin of macrophages from lymphocytes, pure lymphocytes were labelled by incubation for 2 hr at 37’C with 50 ,&/ml tritiated adenosine (specific activity 100-1000 mc/mM; Radiochemical Centre, Amersham). The cells were washed three times in a mixture of isologous serum and T.C. 199 (1: 4) and a sample taken for autoradiography. The labelled cells were then mixed with unlabelled leucocytes (lymphocytes and polymorphs) and cultured for 24 hr, when the cultures were sacrificed and autoradiographed (Ilford L4, nuclear research emulsion). In a further experiment labelled lymphocytes were cultured alone for 24 hr; a second culture of mixed unlabelled leucocytes from the same donor as the lymphocytes was set up and incubated for 24 hr. The two cultures were then combined and incubated for a further 2-3 hr to allow for any phagocytosis of labelled RNA or its derivatives by the macrophages of the mixed unlabelled cultures. Autoradiographs were then made. RESULTS At the commencement of culture the cell population comprised small lymphocytes, a few large lymphocytes, 2 to 5 per cent of monocytes, and about 50 per cent of polymorphs. In the earliest cultures polymorphs and monocytes were often found to contain carbon or silica particles; the small number of macrophages present at 2 hr were probably of monocytic origin. After 4 hr culture an occasional small lymphoid cell, which could not be distinguished morphologically from a small lymphocyte, lvas found to contain a foreign particle. Some larger lymphoid cells were seen which had a larger, paler nucleus, rarely possessing any nucleoli, and a considerable amount of lightly basophilic cytoplasm (Fig. 1). This type of cell was about 10-12 ,U in diameter and also contained foreign particles. Rp 6 hr the macrophages usually had irregular, and sometimes eccentrically placed nuclei, and the basophilic cytoplasm contained numbers of small irregular vacuoles. ,A fe\\- macrophages had a single large qtoplasmic vacuole. These cells bore no morphologic resemblance to monocytes at any time during their morphogenesis. At this time the polymorphs were vacuolated and losing their granulation to a considerable extent. In 16-hr cultures some large macrophages of 20-25 /L were seen. These cells had very pale cytoplasm with indistinct borders and a large, finely textured nucleus. This type of cell \\-as seen in small numbers at all times from 16 hr onwards, and was very similar in morphology to the phagocytic reticulum cell of the lymphoid tissue. Some macrophages contained large amounts of eosinophilic amorphous material which appeared to be cellular in origin, and which may have been derived by the phagocytosis of degenerating polymorphs. =\t this stage vacuolation of the macrophages was a very prominent feature, many of the vacuoles being very much larger than in earlier cells, and in a fe\v cells the cytoplasmic area Experimenial
Cell Reswrch
38
478
J. Gough, M. W. Elves and 41. C. G. IsraZls
Fig. l.--Carbon
containing
cells in 4 hr culture
( x 1600).
w-as tilled with one or t\vo very large vacuoles, the basophilic cytoplasm being confined to a marrow rim around the periphery. By 48 and 72 hr almost all the polymorphs were degenerate, with the exception of eosinophils which remained well preserved. So further qualitative changes were seen in the macrophages. The percentage of macrophages seen at various times is shown in Fig. 2. The figures given represent a mean obtained from the six sets of cultures. From this it will be seen that similar quantitative changes occur in each type of culture, regardless of the nature of the foreign particle present and furthermore macrophage formation will occur in the absence of a foreign stimulant. ,4n initial peak was reached at 10 hr, and was followed by a small fall, rising again to a maximum at 48 hr. After this the percentage of macrophages fell slowly, this being most marked in the cultures containing carbon or silica and may have been due to a damaging effect of these particles within the cell. The labelling experiment showed clearly that some of the macrophages were derived from small lymphocytes. In the initial pure lymphocyte suspension 51 per cent of the cells were labelled and the mean grain count over Experimental
Cell Research 38
Formation
of macrophages
from lymphocytes
in vitro
479
the labelled cells was 17.8 (range 10-42). When performing grain counts only cells containing 10 or more grains were regarded as significantly labelled: the background level gave a random grain count of 4-6 grains per cell. In the cultures combined and incubated for 24 hr 24 per cent of the macrophages were labelled, some of the unlabelled macrophages being derived
I
.
20
’ HOURS
.
’
40 OF
3 60
’
1 80
CULTURE
Fig. Z.-Percentage of macrophages appearing in cultures in the presence of carbon or silica. Control (l)-no foreign particle added; control (2)-carbon added for last 2 hr.
from the unlabelled lymphocytes of the mixed culture, and the mean grain count was almost identical with that of the initial labelled lymphocytes (18.1-range 12-29). When the labelled and unlabelled cultures were combined for the last few hours of culture only very few of the macrophages showed significant degrees of labelling (2-4 per cent), and so reutilization will not explain the appearance of label in the macrophages. The results of the experiments on the effect of polymorphs are shown in Table I from which it is clear that the presence of living polymorphs is required for the transition of lymphocyte to macrophage. This apparent “symbiosis” between these two cell types is at present under further investigation. DISCUSSION
These results lead us to believe that the phagocytic cells can be derived from lymphocytes. At 48 hr almost 35 per cent of the mononuclear cells are Experimental
Cell Research 38
480
J. Gough, M. W. Elves and M. C. G. Isra6ls
macrophages. Not more than 5 per cent of mononuclear cells were monocytes initially, and allowing for the fact that at 48 hr the total number of nongranulocytic cells in a culture is about 50 per cent of that present at 0 hr, and even assuming no monocytes were lost, not more than 10 per cent of the mononuclear cells could be of monocytic origin unless the monocytes had TABLE
I. The effect of polymorphs on the degree of lymphocyte ufter 45 hr of culture. % of macrophages
transformation
present at 48 hr
Culture so.
Cultures of lymphocytes only
Cultures with added living polymorphs
1 2 3 4 5
0 1 0 2 0
33 28 35 30 34
Cultures with added dead polymorphs 1 0 0 1 1
proliferated and undergone rapid mitosis. There is no evidence for this since no mitoses have been seen in any of these cultures; autoradiographs prepared from cultures esposed for 2 hr to tritiated thymidine showed DNA synthesis in less than 1 per cent of the mononuclear cells after 48 to 72 hr of culture, and these cells bore resemblances to early PHA-transformed cells. All stages of transition from the small lymphocyte to a fully developed macrophage were seen, and we therefore believe that the majority of macrophages arose from small lymphocytes. Only a small percentage may possibly have had a monocytic origin. The results of the experiments using labelled lymphocytes proves the lymphocytic origin of some of the macrophages beyond any doubt. Macrophages have been thought to arise from lymphocytes in inflammatory reactions [ 17, 211 and a number of investigators, using plasma-clot culture of buff\; coats, have reported transformation of lymphoid cells to macrophages, polyblasts or monocytes [2, 4,5, 15, 181. Others using similar methods disagree that the precursor of these cells is the lymphocyte [12, 161. In this type of experiment cells were examined by sectioning the clots, whereas the present work had been performed on suspension-cultured cells in smear preparations. This technique has the great advantage over the more classical histological techniques in that the fine detail of the cells is more readily Experimental
Cell Research 38
Formation
of macrophayes
from lymphocytes
in vitro
481
discernible and small changes more easily detected. It is moreover difficult to distinguish similar cell types in sections. Using our technique it is also possible to carry out detailed differential counts which are difficult in histological material. Berman and Stulberg [3] have obtained similar results in a different fluid culture system and they thought, on purely morphological grounds, that most of the macrophages had arisen from lymphocytes. They did not, however, carry out any differential counts on serial specimens obtained from their cultures. Schrek and Rabinowitz [23] noted the presence of macrophages in cultures of human leucocyte suspensions and found that the number of macrophages was greatly reduced if PHA was present in the culture medium. They considered these cells to have developed from monocytes because in earlier studies of pure cultures of small lymphocytes, obtained from peripheral blood by separation on a glass wool column, no macrophage formation was observed, whereas in cultures in which lymphocytes had been killed by irradiation some macrophages were seen [2O]. Our own studies detailed is necessary for the above lead us to suggest that presence of polymorphs lymphocyte transformation; if this is so Schrek’s results are easily explained. Our demonstration of a relationship between polymorphonuclear cells and lymphocytes will also explain a number of discrepancies in the early literature. llloom [J] cultured cells obtained from the thoracic duct of rabbits via a tear in the wall of the duct and observed transformation to macrophages. Hall and Furth [12] and Lledawar [16] repeated the experiment with negative results, but obtained the lymphocytes via a needle inserted into the duct. n’hen Rledawar [16] obtained cells through a tear in the duct wall macrocounts showed that the initial cell phages appeared in cultures. Differential population obtained by the tear method contained considerable numbers of granulocytes, whereas very few \vere present in the cultures of cells ohtainerl via the cannula. Our studies thus demonstrate yet another developmental potentiality of the small lymphocyte; transformation to a phagocytic macrocyte.
SUMMARY
The appearance of macrophages is described in fluid cultures of leucocytes obtained from human peripheral blood. When lymphocytes labelled with tritiated adenosine are cultured some of the macrophages are subsequently Experimental
Cell Research 38
452
J. Gough, M. W. Elves rind M. C. G. IsraFls
seen to contain the radioactive marker, and it is considered that the small lymphocyte is capable of transformation into a macrophage. The presence of living polymorphs has been shown to be necessary for the transformation to occur. REFERENCES 1. AWRORO~, P. P. and TIMOFEJEWSKI, J. A. D., I’irchoms birch. Patho/. Anat. 216, 184 (1914). BERMAX, L., Arch. Pathol. 33, 295 (1942). BERMAN, L. and STULBERG, C. S., Lab. Inuest. 11, 1323 (1963). BLOOM, W. H., Proc. Sot. Exptl Biol. N.Y. 24, 567 (1927). DE BRUYN, P. P. H., Anat. Rec. 93, 295 (1945). CAFFIER, P., Arch. exptl Zellforsch. 6, 285 (1928). 7. CARSTAIRS, K., Lancet i, 829 (1962). 8. COOPER, E. H., BARKIIAM, P. and HALE, A. J., Lancet ii, 210 (1961). J. I~., Nafure (Lond.) 194, 1257 (1962). 9. ELVES, 111. W. and WILKINSON, 10. ELVES, M. W., ROATH, S. and ISRA~LS, M. C. G., Lancet i, 806 (1963). 11. DE HAAN, J., Arch. exptl Zellforsch. 3, 219 (1927). 12. HALL, J. W. and FURTH, J., Arch. Pathol. 25, 46 (1938). D. A., DONELLY, A. J., NOWELL, P. C. and BECK, S., Am. J. Ham. Genet. 11, 13. HUXGERFORD,
2. 3. 4. 5. 6.
215 (1959). 14. MACKINNEY, A. A., STOHLMAN, Y. and BRECHER, G., Blood 19, 349 (1962). 15. MAXIMOW, A., Arch. exptl Zellforsch. 5, 169 (1928). 16. MEDAWAR, J., Brit. J. Exptl Path. 21, 205 (1940). 17. METCHNIKOFF, El., Virchows Arch. Pathol. Anat. 113, 63 (1888). 18. MURRAY, R. G., Am. J. Anat. 81, 369 (1947). 19. PEARMAIN, G. E., LYCETTE, R. R. and FITZGEHALD, P. H., Lance1 i, 638 (1963). 20. RABINOWITZ, Y. and SCHREK, R., Proc. Sot. Exptl Biol. N.Y. 110, 429 (1962). 21. REBUCK, J. W., MONTO, P. W., MONAGHA~X, E. A. and RIDDLE, J. M., Ann. N. Y. Acad. Sci. 56, 748 (1958). 22. SCHREK, R., Am. Rev. Resp. Dis. 87, 734 (1963). 23. SCIIREK, R. and RABINO~ITZ, Y., Proc. Sot. Expptl Bio!. N. Y. 113, 191 (1963).
Experimental
Cell Research 38
Experimental
THE
FORMATION
OF MACROPHAGES
LYMPHOCYTES J. GOUGH, Department
Haematology, Manchester,
FROM
IN VITRO
M. W. ELVES
of Clinical
Cell Research 38, 476-482 (IDC5)
and M. C. G. ISRAeLS University England
and Royal Injirmary,
Received September 4, 1964
THE transformation of lymphocytes into “blast”-like cells under the influence of phytohaemagglutinin (PHA) [7, 8, 9, 141 and various antigens [lo, 19, 221 is well established. The formation of macrophages in hangingdrop cultures of leucocytes has been known for many years [ 1, 6, 11, 15 ], but comparatively little attention has been paid in recent years to the development of such cells when fluid culture media are used. The present investigations were performed to assess the degree of macrophage formation in vitro and to determine the origin of these cells. The recognition of macrophages in leucocyte cultures is considered to be important in view of the fact that some of the cells bear superficial resemblances to the “blast”-like cells of PHA and antigen cultures.
MATERIALS
AND
METHODS
Leucocyte cultures were prepared using normal human blood by the method of Hungerford et al. [13] except that PHA was not added. In each experiment four sets of cultures were made. Carbon particles in the form of Indian ink were added to each culture of the first set, and similarly very fine silica particles were added to the second set. In the third set carbon was added 2 hr before the cultures were sacrificed, while the fourth set was untreated and acted as a control. Cultures were incubated at 37°C and sacrificed at various intervals from 0 to 72 hr. The experiments were repeated on five occasions using different leucocyte donors. Smears of the centrifuged cellular deposits were made and stained by Jenner-Giemsa stain. In order to investigate the relationship between the lymphocytes and the polymorphs in these cultures the following additional experiment was performed. Pure lymphocyte cultures were obtained by separating the lymphocytes from the other cells by incubation of the cell/plasma suspension on cotton wool columns at 37°C for l-2 hr and eluting the viable lymphocytes with culture medium. Some of these cultures were left untreated whilst polymorphs were added to others. To determine the necessity for living polymorphs, heat-killed polymorphs were added to other pure lymphocyte cultures. Cultures were then examined in the usual way. Experimental
Cell Research 38
Formation
of macrophages from lymphocytes
in vitro
177
In order to demonstrate the origin of macrophages from lymphocytes, pure lymphocytes were labelled by incubation for 2 hr at 37’C with 50 ,&/ml tritiated adenosine (specific activity 100-1000 mc/mM; Radiochemical Centre, Amersham). The cells were washed three times in a mixture of isologous serum and T.C. 199 (1: 4) and a sample taken for autoradiography. The labelled cells were then mixed with unlabelled leucocytes (lymphocytes and polymorphs) and cultured for 24 hr, when the cultures were sacrificed and autoradiographed (Ilford L4, nuclear research emulsion). In a further experiment labelled lymphocytes were cultured alone for 24 hr; a second culture of mixed unlabelled leucocytes from the same donor as the lymphocytes was set up and incubated for 24 hr. The two cultures were then combined and incubated for a further 2-3 hr to allow for any phagocytosis of labelled RNA or its derivatives by the macrophages of the mixed unlabelled cultures. Autoradiographs were then made. RESULTS At the commencement of culture the cell population comprised small lymphocytes, a few large lymphocytes, 2 to 5 per cent of monocytes, and about 50 per cent of polymorphs. In the earliest cultures polymorphs and monocytes were often found to contain carbon or silica particles; the small number of macrophages present at 2 hr were probably of monocytic origin. After 4 hr culture an occasional small lymphoid cell, which could not be distinguished morphologically from a small lymphocyte, lvas found to contain a foreign particle. Some larger lymphoid cells were seen which had a larger, paler nucleus, rarely possessing any nucleoli, and a considerable amount of lightly basophilic cytoplasm (Fig. 1). This type of cell was about 10-12 ,U in diameter and also contained foreign particles. Rp 6 hr the macrophages usually had irregular, and sometimes eccentrically placed nuclei, and the basophilic cytoplasm contained numbers of small irregular vacuoles. ,A fe\\- macrophages had a single large qtoplasmic vacuole. These cells bore no morphologic resemblance to monocytes at any time during their morphogenesis. At this time the polymorphs were vacuolated and losing their granulation to a considerable extent. In 16-hr cultures some large macrophages of 20-25 /L were seen. These cells had very pale cytoplasm with indistinct borders and a large, finely textured nucleus. This type of cell \\-as seen in small numbers at all times from 16 hr onwards, and was very similar in morphology to the phagocytic reticulum cell of the lymphoid tissue. Some macrophages contained large amounts of eosinophilic amorphous material which appeared to be cellular in origin, and which may have been derived by the phagocytosis of degenerating polymorphs. =\t this stage vacuolation of the macrophages was a very prominent feature, many of the vacuoles being very much larger than in earlier cells, and in a fe\v cells the cytoplasmic area Experimenial
Cell Reswrch
38
478
J. Gough, M. W. Elves and 41. C. G. IsraZls
Fig. l.--Carbon
containing
cells in 4 hr culture
( x 1600).
w-as tilled with one or t\vo very large vacuoles, the basophilic cytoplasm being confined to a marrow rim around the periphery. By 48 and 72 hr almost all the polymorphs were degenerate, with the exception of eosinophils which remained well preserved. So further qualitative changes were seen in the macrophages. The percentage of macrophages seen at various times is shown in Fig. 2. The figures given represent a mean obtained from the six sets of cultures. From this it will be seen that similar quantitative changes occur in each type of culture, regardless of the nature of the foreign particle present and furthermore macrophage formation will occur in the absence of a foreign stimulant. ,4n initial peak was reached at 10 hr, and was followed by a small fall, rising again to a maximum at 48 hr. After this the percentage of macrophages fell slowly, this being most marked in the cultures containing carbon or silica and may have been due to a damaging effect of these particles within the cell. The labelling experiment showed clearly that some of the macrophages were derived from small lymphocytes. In the initial pure lymphocyte suspension 51 per cent of the cells were labelled and the mean grain count over Experimental
Cell Research 38
Formation
of macrophages
from lymphocytes
in vitro
479
the labelled cells was 17.8 (range 10-42). When performing grain counts only cells containing 10 or more grains were regarded as significantly labelled: the background level gave a random grain count of 4-6 grains per cell. In the cultures combined and incubated for 24 hr 24 per cent of the macrophages were labelled, some of the unlabelled macrophages being derived
I
.
20
’ HOURS
.
’
40 OF
3 60
’
1 80
CULTURE
Fig. Z.-Percentage of macrophages appearing in cultures in the presence of carbon or silica. Control (l)-no foreign particle added; control (2)-carbon added for last 2 hr.
from the unlabelled lymphocytes of the mixed culture, and the mean grain count was almost identical with that of the initial labelled lymphocytes (18.1-range 12-29). When the labelled and unlabelled cultures were combined for the last few hours of culture only very few of the macrophages showed significant degrees of labelling (2-4 per cent), and so reutilization will not explain the appearance of label in the macrophages. The results of the experiments on the effect of polymorphs are shown in Table I from which it is clear that the presence of living polymorphs is required for the transition of lymphocyte to macrophage. This apparent “symbiosis” between these two cell types is at present under further investigation. DISCUSSION
These results lead us to believe that the phagocytic cells can be derived from lymphocytes. At 48 hr almost 35 per cent of the mononuclear cells are Experimental
Cell Research 38
480
J. Gough, M. W. Elves and M. C. G. Isra6ls
macrophages. Not more than 5 per cent of mononuclear cells were monocytes initially, and allowing for the fact that at 48 hr the total number of nongranulocytic cells in a culture is about 50 per cent of that present at 0 hr, and even assuming no monocytes were lost, not more than 10 per cent of the mononuclear cells could be of monocytic origin unless the monocytes had TABLE
I. The effect of polymorphs on the degree of lymphocyte ufter 45 hr of culture. % of macrophages
transformation
present at 48 hr
Culture so.
Cultures of lymphocytes only
Cultures with added living polymorphs
1 2 3 4 5
0 1 0 2 0
33 28 35 30 34
Cultures with added dead polymorphs 1 0 0 1 1
proliferated and undergone rapid mitosis. There is no evidence for this since no mitoses have been seen in any of these cultures; autoradiographs prepared from cultures esposed for 2 hr to tritiated thymidine showed DNA synthesis in less than 1 per cent of the mononuclear cells after 48 to 72 hr of culture, and these cells bore resemblances to early PHA-transformed cells. All stages of transition from the small lymphocyte to a fully developed macrophage were seen, and we therefore believe that the majority of macrophages arose from small lymphocytes. Only a small percentage may possibly have had a monocytic origin. The results of the experiments using labelled lymphocytes proves the lymphocytic origin of some of the macrophages beyond any doubt. Macrophages have been thought to arise from lymphocytes in inflammatory reactions [ 17, 211 and a number of investigators, using plasma-clot culture of buff\; coats, have reported transformation of lymphoid cells to macrophages, polyblasts or monocytes [2, 4,5, 15, 181. Others using similar methods disagree that the precursor of these cells is the lymphocyte [12, 161. In this type of experiment cells were examined by sectioning the clots, whereas the present work had been performed on suspension-cultured cells in smear preparations. This technique has the great advantage over the more classical histological techniques in that the fine detail of the cells is more readily Experimental
Cell Research 38
Formation
of macrophayes
from lymphocytes
in vitro
481
discernible and small changes more easily detected. It is moreover difficult to distinguish similar cell types in sections. Using our technique it is also possible to carry out detailed differential counts which are difficult in histological material. Berman and Stulberg [3] have obtained similar results in a different fluid culture system and they thought, on purely morphological grounds, that most of the macrophages had arisen from lymphocytes. They did not, however, carry out any differential counts on serial specimens obtained from their cultures. Schrek and Rabinowitz [23] noted the presence of macrophages in cultures of human leucocyte suspensions and found that the number of macrophages was greatly reduced if PHA was present in the culture medium. They considered these cells to have developed from monocytes because in earlier studies of pure cultures of small lymphocytes, obtained from peripheral blood by separation on a glass wool column, no macrophage formation was observed, whereas in cultures in which lymphocytes had been killed by irradiation some macrophages were seen [2O]. Our own studies detailed is necessary for the above lead us to suggest that presence of polymorphs lymphocyte transformation; if this is so Schrek’s results are easily explained. Our demonstration of a relationship between polymorphonuclear cells and lymphocytes will also explain a number of discrepancies in the early literature. llloom [J] cultured cells obtained from the thoracic duct of rabbits via a tear in the wall of the duct and observed transformation to macrophages. Hall and Furth [12] and Lledawar [16] repeated the experiment with negative results, but obtained the lymphocytes via a needle inserted into the duct. n’hen Rledawar [16] obtained cells through a tear in the duct wall macrocounts showed that the initial cell phages appeared in cultures. Differential population obtained by the tear method contained considerable numbers of granulocytes, whereas very few \vere present in the cultures of cells ohtainerl via the cannula. Our studies thus demonstrate yet another developmental potentiality of the small lymphocyte; transformation to a phagocytic macrocyte.
SUMMARY
The appearance of macrophages is described in fluid cultures of leucocytes obtained from human peripheral blood. When lymphocytes labelled with tritiated adenosine are cultured some of the macrophages are subsequently Experimental
Cell Research 38
452
J. Gough, M. W. Elves rind M. C. G. IsraFls
seen to contain the radioactive marker, and it is considered that the small lymphocyte is capable of transformation into a macrophage. The presence of living polymorphs has been shown to be necessary for the transformation to occur. REFERENCES 1. AWRORO~, P. P. and TIMOFEJEWSKI, J. A. D., I’irchoms birch. Patho/. Anat. 216, 184 (1914). BERMAX, L., Arch. Pathol. 33, 295 (1942). BERMAN, L. and STULBERG, C. S., Lab. Inuest. 11, 1323 (1963). BLOOM, W. H., Proc. Sot. Exptl Biol. N.Y. 24, 567 (1927). DE BRUYN, P. P. H., Anat. Rec. 93, 295 (1945). CAFFIER, P., Arch. exptl Zellforsch. 6, 285 (1928). 7. CARSTAIRS, K., Lancet i, 829 (1962). 8. COOPER, E. H., BARKIIAM, P. and HALE, A. J., Lancet ii, 210 (1961). J. I~., Nafure (Lond.) 194, 1257 (1962). 9. ELVES, 111. W. and WILKINSON, 10. ELVES, M. W., ROATH, S. and ISRA~LS, M. C. G., Lancet i, 806 (1963). 11. DE HAAN, J., Arch. exptl Zellforsch. 3, 219 (1927). 12. HALL, J. W. and FURTH, J., Arch. Pathol. 25, 46 (1938). D. A., DONELLY, A. J., NOWELL, P. C. and BECK, S., Am. J. Ham. Genet. 11, 13. HUXGERFORD,
2. 3. 4. 5. 6.
215 (1959). 14. MACKINNEY, A. A., STOHLMAN, Y. and BRECHER, G., Blood 19, 349 (1962). 15. MAXIMOW, A., Arch. exptl Zellforsch. 5, 169 (1928). 16. MEDAWAR, J., Brit. J. Exptl Path. 21, 205 (1940). 17. METCHNIKOFF, El., Virchows Arch. Pathol. Anat. 113, 63 (1888). 18. MURRAY, R. G., Am. J. Anat. 81, 369 (1947). 19. PEARMAIN, G. E., LYCETTE, R. R. and FITZGEHALD, P. H., Lance1 i, 638 (1963). 20. RABINOWITZ, Y. and SCHREK, R., Proc. Sot. Exptl Biol. N.Y. 110, 429 (1962). 21. REBUCK, J. W., MONTO, P. W., MONAGHA~X, E. A. and RIDDLE, J. M., Ann. N. Y. Acad. Sci. 56, 748 (1958). 22. SCHREK, R., Am. Rev. Resp. Dis. 87, 734 (1963). 23. SCIIREK, R. and RABINO~ITZ, Y., Proc. Sot. Expptl Bio!. N. Y. 113, 191 (1963).
Experimental
Cell Research 38