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Pores of the Palatine Tonsillar Crypt and Pharyngeal Tonsillar Recess
Auris ' Nasus ' Larynx (Tokyo) 6,23-30,1979
PORES OF THE PALATINE TONSILLAR CRYPT AND PHARYNGEAL TONSILLAR RECESS -A SCANNING ELECTRON MICROSCOPIC STUDYAkira KODAMA, M.D./ and Tomoyuki HOSHINO, M.D.2 lDepartment of Otolaryngology, Teikyo University School of Medicine, Tokyo, Japan 2Department of Otolaryngology, Hamamatsu Medical School, Shizuoka, Japan
The crypt of the palatine tonsil and the recess of the human pharyngeal tonsil were studied using a scanning electron microscope. Many pores, ranging in diameter from 10 to 100 .urn, were observed on the luminal surface of the crypts. All of the crypt surface except at the sites of pores was covered by epithelial cells. Non-epithelial round cells, mostly lymphocytes, were exposed directly to the crypt lumen through these pores. In the lumen of palatine tonsillar crypts, numerous round cells were present which evidently pass through these pores from the parenchyma. This finding indicates that the tonsillar parenchyma is directly open to the crypt. Similar findings were obtained in the recess of the pharyngeal tonsil. According to recent immunological studies, the tonsils produce immunoglobulin which provides resistance against pathogenic organisms. Distribution of immunoglobulin in the palatine tonsil has been studied using fluorescent antibody techniques by many investigators. The crypts of the tonsils are the places of initial contact between the various antigen and lymphocytes which immigrated from the parenchyma. Immunoglobulin, especially IgG and IgA, was found to be distributed in the subepithelial area of the crypt (HAMASHIMA, 1970) and aggregations of plasmacytic series cell, containing immunoglobulin, have been found in the crypt epithelium (SCHMEDTJE and BATTEs, 1973). In contrast, only a trace amount of IgG and IgA was present in the stratified epithelial cells of the free surface facing the oral cavity (SCHMEDTJE and BATrES, 1973). These immunohistologic studies suggest that the crypt epithelium is closely related to the immunological function of the tonsillar parenchyma. The scanning electron microscope (SEM) can be used to observe the luminal surface of the tonsillar crypt. A few scanning electron microscopic studies of the Received for publication September 9, 1978 23
24
A. KODAMA and T. HOSHINO
palatine tonsil, concerning mainly the inner structure, already have been reported (LENZ, 1972; KAWABATA, 1976; UMETANI, 1977). In the present paper, the surface structure of the crypt and recess of the tonsillar tissues were studied using SEM. MATERIAL AND METHOD
The materials were the palatine and pharyngeal tonsils taken from 11 patients, ranging in age from 4 to 10 years, during tonsillectomy and adnoidectomy. After removal, the tonsils were immediately chopped into several blocks, washed with 0.9 % saline solution, fixed with 2 % glutaraldehyde in 0.1 M phosphate buffer (pH 7.4) and then treated with glutamic acid and tannic acid solutions (MURAKAMI'S electron-conductive method, 1974). After fixation with 1 % OS04, these blocks were dehydrated with graded ethanol and transferred to amyl acetate. After critical point drying with liquid carbon dioxide, the specimens were coated with Au-Pd in an ion sputter (Eiko ion coater IB-3), and then studied under a Hitachi HHS-2R scanning electron microscope. FINDINGS
1) Palatine tonsils A palatine tonsil has 10 to 20 complexly and deeply invaginated crypts. Most crypts are deep and reach even to the tonsillar capsule. Each crypt has a wide luminal surface with a narrow orifice. According to our observation, the crypt surface was generally covered with a similar epithelium on the free surface of the palatine tonsil facing the oral cavity. These epithelial cells, probably squamous cells, had many microridges on the free cell surface (Fig. I-A). Other parts of the crypt surface were covered less extensively by cells with microvilli (Fig. I-B). The ciliated cells were seen in more restricted areas (Fig. I-C). Many round- or oval-shaped pores were observed in the luminal surface, and they were distributed from the crypt orifice to the bottom. These pores showed an irregular distribution pattern. Figure 2 illustrates the concentrated areas of the pores. The pores seemed to be more numerous on the crypt surface covering the germinal center (Fig. 3). The diameters of these pores ranged from 10 to lOO.um (Fig. 4). Non-epithelial round cells were found within the pores. They were also seen in the lumen of the crypt. The presence of this pore structure was confirmed under a light microscope; many lymphocytes were found in the crypt lumen (Fig. 5). 2)
Pharyngeal tonsils Most parts of the free surface of the pharyngeal tonsils facing the pharyngeal cavity were covered with ciliated cells. Non-ciliated cells with microvilli were less common.
PORES OF THE PALATINE TONSILLAR CRYPT
25
Fig. 1. Three types of cell from the crypt epithelium (A, B, C). A: Squamous cells with microridges on the free surface of the cell. B: Non-ciliated cells with microvilli. C: Ciliated cells. For the most part, the crypt surface was covered by the cells shown in A. Scale bars equal 3 pm.
Fig. 2. The crypt surface of the palatine tonsil. Pores (white arrows) and round cells (black arrows) were evident in the crypt lumen. Scale bars equal 60 pm.
26
A. KODAMA and T. HOSHINO
Fig. 3. The pores on the crypt surface and the tonsillar parenchyma. Pores (arrows) are seen on the crypt surface covering the germinal center (asterisk). Scale bars equal 80 f,m.
The pharyngeal tonsils have 4 to 5 deep recesses parallel to the sagittal plane. The recesses had a structure similar to the crypts of the palatine tonsil. Most of the luminal surface of the recess as covered by non-ciliated cells without microvilli. Many small pores were also observed on the surface of the recess. The diameters of pores ranged from 10 to 30 ,urn. Round cells were observed in these pores. COMMENT
The tonsils, as a lymphocytogenic organ, are unique in that they are covered by epithelium. The overlying epithelium invaginates into the parenchyma forming crypts, whose epithelium is different from that facing the oral cavity. In the palatine tonsillar epithelium facing the oral cavity, a distinct basement membrane and dense collagenous connective tissue layer are found beneath the epithelium. In the deeper portions of the crypts, however, it has been reported that the basement membrane beneath the epithelium is loose to varying degrees (OGINO, 1959). Also the epithelium is heavily infiltrated with lymphocytes (STOHR, 1891; FIORETTI, 1961). STOHR (1891) indicated that the epithelium lining each crypt was infiltrated with lymphocytes. This epithelial structure was generally referred to as "lymphoepithelial symbiosis" (FIORRETTI, 1961). Recently, KAWAGUCHI (1967) showed the details of this symbiosis by transmission electron microscope (TEM);
PORES OF THE PALATINE TONSILLAR CRYPT
27
Fig. 4. A pore on the crypt surface. The pores had various sizes: small (A) and large (B). Non-epithelial round cells were found in the pores. Scale bar equals 2 ,urn (A), 10 ,urn (B).
28
A. KODAMA and T. HOSHINO
Fig. 5. A paraffin section of the palatine tonsil (H-E stain). Pores (arrows), which look the same as the pores viewed under SEM, were also observed on the crypt epithelium of the palatine tonsil. Asterisk: the crypt lumen.
this was also observed by TEM in the pharyngeal tonsil (TSUCHII, 1974). It is generally believed that the lymphoepithelial symbiosis of the crypt epithelium plays an important role in the immunological function of the tonsil. The lumen of the crypts is known to contain large accumulations of living and degenerated lymphocytes mixed with desquamated squamous epithelial cells, granular detritus and micro-organisms. These lymphocytes pass apparently through the epithelium from the parenchyma into the lumen of the crypt. All of the crypt surface, however, had been thought to be covered by the epithelial cells, and until now no structural evidence had been reported to account for this cell migration. As was reported previously (KODAMA et ai., 1977; KODAMA et ai., 1978), in the present study many pores were found in the crypt surface of the palatine tonsil and the recess surface of the pharyngeal tonsil. Moreover, the non-epithelial round cells were seen in the pores, which resembled lymphocytes. These lympho-
PORES OF THE PALATINE TONSILLAR CRYPT
29
cytes pass through these pores from the subepithelial lymphoid tissue into the crypt lumen. Consequently, the tonsillar parenchyma is left open to the crypt and recess lumen through these pores. Although the depth of the pores could not be determined accurately, the pores seem to go through the crypt epithelium all the way to the parenchyma. SUKO (1960) and FALK (1963) reported that lymphocytes immigrate into the crypt epithelium of fetus; lymphocytes were observed in the fetal crypt lumen unassociated with pathological conditions. These findings suggest the presence of pores in the tonsillar crypt in fetus as is shown in the children of this study. Recently, KAWABATA (1978) also observed pores of the tonsillar crypt. He suggested that the pore closes by the insertion of a plug from below and opens by the degeneration of the plug. The crypt epithelium is the place initial contact with invading antigens. The pores of the crypt become the pathway between the tonsillar parenchyma and the crypt lumen possessing extrinsic factors. These pores appear to be important structures for immunological function of the tonsil. The authors are indebted to Drs. Jun-Ichi Suzuki and Tetsuo Ishii (Teikyo University) for their advice and encouragement on this study and to Dr. Robert F. Hink who helped us to prepare the English manuscript.
REFERENCES FALK, P.: Entwicklungsgeschichte, Anatomie, Missbildungen, Physiologie und Pathologie des Rachens (einschliesslich Tonsillen). Berendes, J., Link, R., und Zollner, R., eds. HalsNasen-Ohren HeiIkunde, II/I G Thieme Stuttgart, 1963. FIORETTI, A.: Die Gaumenmandel. G Thieme Verlag Stuttgart, 1961. HAMASHIMA, T.: Immunohistological studies on human palatine tonsils (in Japanese). Jpn. J. Tonsil. 9: 118-128, 1970. KA WABATA, I.: Scanning electron microscopic observations of the human palatine tonsils (in Japanese). Jpn. J. Otol. 79: 733-740, 1976. KAWABATA, I.: The surface structure of human tonsillar crypts-scanning electron microscopic observation (in Japanese). Jpn. J. Tonsil. 17: 204-210, 1978. KAWAGUCHI, E.: Ultrastructure of human palatine tonsil. 1. Electron microscopic studies on tonsillar mucous epithelium (in Japanese). Sapporo Med. J. 31: 144-165, 1967. KODAMA, A. et al.: Scanning electron microscopic study of human tonsillar crypt (in Japanese). Practica Otologica (Kyoto) 70: 479-486, 1977. KODAMA, A. et al.: Scanning electron microscopic study of human pharyngeal tonsil (in Japanese). Practica Otologica (Kyoto) 71: 1017-1023, 1978. LENz, H.: Raumliche Betrachtungen der Tonsilleninnenstruktur mit Hilfe des Rasterelektronenmikroskops. Z. Laryngol. Rhinol. Otol. Ihre Grenzgeb. 51: 262-274, 1972. MURAKAMI, T.: A revised tannin-osmium methods for non-coated scanning electron microscopic specimens. Arch. Histol. Jpn. (Niggata Jpn.) 36: 189-193, 1974. OGINO, Y.: Pathomorphologic studies on the subepithelial basal membrane of the human palatine tonsil (in Japanese). J. Nippon Med. Sch. 18: 1311-1318, 1959. SCHMEDTJE, J. E., and BATTES A. F.: Immunoglobulins and blood vessels in the tonsillar crypt epithelium. Ann. Otol. 82: 359-369, 1973. ST()HR: Uber die Mandeln und deren Entwickelung. Anat. Anz. S. 545: 6, 1891.
A. KODAMA and T. HOSHINO
30
SUKO, H.: Histogenic study of palatine tonsil of human fetus, with special reference on interstitial connective tissue (in Japanese). Jpn. J. 0101.63: 907-924, 1960. TSUCHII, Y.: Electron microscopic studies of the pharyngeal tonsil (in Japanese). Jpn. J. TOllSil. 13: 26-29, 1974. UMETANI, Y.: Postcapillary venule in rabbit tonsil and entry of lymphocytes into its endothelium: a scanning and transmission electron microscopic study. Arch. Hislal. Jpn. 40: 77-94, 1977.
Request reprints from:
Dr. Akira Kodama, Department of Otolaryngology, Teikyo University School of Medicine, Kaga 2-11-1, Itabashi-ku, Tokyo 173, Japan
PORES OF THE PALATINE TONSILLAR CRYPT AND PHARYNGEAL TONSILLAR RECESS -A SCANNING ELECTRON MICROSCOPIC STUDYAkira KODAMA, M.D./ and Tomoyuki HOSHINO, M.D.2 lDepartment of Otolaryngology, Teikyo University School of Medicine, Tokyo, Japan 2Department of Otolaryngology, Hamamatsu Medical School, Shizuoka, Japan
The crypt of the palatine tonsil and the recess of the human pharyngeal tonsil were studied using a scanning electron microscope. Many pores, ranging in diameter from 10 to 100 .urn, were observed on the luminal surface of the crypts. All of the crypt surface except at the sites of pores was covered by epithelial cells. Non-epithelial round cells, mostly lymphocytes, were exposed directly to the crypt lumen through these pores. In the lumen of palatine tonsillar crypts, numerous round cells were present which evidently pass through these pores from the parenchyma. This finding indicates that the tonsillar parenchyma is directly open to the crypt. Similar findings were obtained in the recess of the pharyngeal tonsil. According to recent immunological studies, the tonsils produce immunoglobulin which provides resistance against pathogenic organisms. Distribution of immunoglobulin in the palatine tonsil has been studied using fluorescent antibody techniques by many investigators. The crypts of the tonsils are the places of initial contact between the various antigen and lymphocytes which immigrated from the parenchyma. Immunoglobulin, especially IgG and IgA, was found to be distributed in the subepithelial area of the crypt (HAMASHIMA, 1970) and aggregations of plasmacytic series cell, containing immunoglobulin, have been found in the crypt epithelium (SCHMEDTJE and BATTEs, 1973). In contrast, only a trace amount of IgG and IgA was present in the stratified epithelial cells of the free surface facing the oral cavity (SCHMEDTJE and BATrES, 1973). These immunohistologic studies suggest that the crypt epithelium is closely related to the immunological function of the tonsillar parenchyma. The scanning electron microscope (SEM) can be used to observe the luminal surface of the tonsillar crypt. A few scanning electron microscopic studies of the Received for publication September 9, 1978 23
24
A. KODAMA and T. HOSHINO
palatine tonsil, concerning mainly the inner structure, already have been reported (LENZ, 1972; KAWABATA, 1976; UMETANI, 1977). In the present paper, the surface structure of the crypt and recess of the tonsillar tissues were studied using SEM. MATERIAL AND METHOD
The materials were the palatine and pharyngeal tonsils taken from 11 patients, ranging in age from 4 to 10 years, during tonsillectomy and adnoidectomy. After removal, the tonsils were immediately chopped into several blocks, washed with 0.9 % saline solution, fixed with 2 % glutaraldehyde in 0.1 M phosphate buffer (pH 7.4) and then treated with glutamic acid and tannic acid solutions (MURAKAMI'S electron-conductive method, 1974). After fixation with 1 % OS04, these blocks were dehydrated with graded ethanol and transferred to amyl acetate. After critical point drying with liquid carbon dioxide, the specimens were coated with Au-Pd in an ion sputter (Eiko ion coater IB-3), and then studied under a Hitachi HHS-2R scanning electron microscope. FINDINGS
1) Palatine tonsils A palatine tonsil has 10 to 20 complexly and deeply invaginated crypts. Most crypts are deep and reach even to the tonsillar capsule. Each crypt has a wide luminal surface with a narrow orifice. According to our observation, the crypt surface was generally covered with a similar epithelium on the free surface of the palatine tonsil facing the oral cavity. These epithelial cells, probably squamous cells, had many microridges on the free cell surface (Fig. I-A). Other parts of the crypt surface were covered less extensively by cells with microvilli (Fig. I-B). The ciliated cells were seen in more restricted areas (Fig. I-C). Many round- or oval-shaped pores were observed in the luminal surface, and they were distributed from the crypt orifice to the bottom. These pores showed an irregular distribution pattern. Figure 2 illustrates the concentrated areas of the pores. The pores seemed to be more numerous on the crypt surface covering the germinal center (Fig. 3). The diameters of these pores ranged from 10 to lOO.um (Fig. 4). Non-epithelial round cells were found within the pores. They were also seen in the lumen of the crypt. The presence of this pore structure was confirmed under a light microscope; many lymphocytes were found in the crypt lumen (Fig. 5). 2)
Pharyngeal tonsils Most parts of the free surface of the pharyngeal tonsils facing the pharyngeal cavity were covered with ciliated cells. Non-ciliated cells with microvilli were less common.
PORES OF THE PALATINE TONSILLAR CRYPT
25
Fig. 1. Three types of cell from the crypt epithelium (A, B, C). A: Squamous cells with microridges on the free surface of the cell. B: Non-ciliated cells with microvilli. C: Ciliated cells. For the most part, the crypt surface was covered by the cells shown in A. Scale bars equal 3 pm.
Fig. 2. The crypt surface of the palatine tonsil. Pores (white arrows) and round cells (black arrows) were evident in the crypt lumen. Scale bars equal 60 pm.
26
A. KODAMA and T. HOSHINO
Fig. 3. The pores on the crypt surface and the tonsillar parenchyma. Pores (arrows) are seen on the crypt surface covering the germinal center (asterisk). Scale bars equal 80 f,m.
The pharyngeal tonsils have 4 to 5 deep recesses parallel to the sagittal plane. The recesses had a structure similar to the crypts of the palatine tonsil. Most of the luminal surface of the recess as covered by non-ciliated cells without microvilli. Many small pores were also observed on the surface of the recess. The diameters of pores ranged from 10 to 30 ,urn. Round cells were observed in these pores. COMMENT
The tonsils, as a lymphocytogenic organ, are unique in that they are covered by epithelium. The overlying epithelium invaginates into the parenchyma forming crypts, whose epithelium is different from that facing the oral cavity. In the palatine tonsillar epithelium facing the oral cavity, a distinct basement membrane and dense collagenous connective tissue layer are found beneath the epithelium. In the deeper portions of the crypts, however, it has been reported that the basement membrane beneath the epithelium is loose to varying degrees (OGINO, 1959). Also the epithelium is heavily infiltrated with lymphocytes (STOHR, 1891; FIORETTI, 1961). STOHR (1891) indicated that the epithelium lining each crypt was infiltrated with lymphocytes. This epithelial structure was generally referred to as "lymphoepithelial symbiosis" (FIORRETTI, 1961). Recently, KAWAGUCHI (1967) showed the details of this symbiosis by transmission electron microscope (TEM);
PORES OF THE PALATINE TONSILLAR CRYPT
27
Fig. 4. A pore on the crypt surface. The pores had various sizes: small (A) and large (B). Non-epithelial round cells were found in the pores. Scale bar equals 2 ,urn (A), 10 ,urn (B).
28
A. KODAMA and T. HOSHINO
Fig. 5. A paraffin section of the palatine tonsil (H-E stain). Pores (arrows), which look the same as the pores viewed under SEM, were also observed on the crypt epithelium of the palatine tonsil. Asterisk: the crypt lumen.
this was also observed by TEM in the pharyngeal tonsil (TSUCHII, 1974). It is generally believed that the lymphoepithelial symbiosis of the crypt epithelium plays an important role in the immunological function of the tonsil. The lumen of the crypts is known to contain large accumulations of living and degenerated lymphocytes mixed with desquamated squamous epithelial cells, granular detritus and micro-organisms. These lymphocytes pass apparently through the epithelium from the parenchyma into the lumen of the crypt. All of the crypt surface, however, had been thought to be covered by the epithelial cells, and until now no structural evidence had been reported to account for this cell migration. As was reported previously (KODAMA et ai., 1977; KODAMA et ai., 1978), in the present study many pores were found in the crypt surface of the palatine tonsil and the recess surface of the pharyngeal tonsil. Moreover, the non-epithelial round cells were seen in the pores, which resembled lymphocytes. These lympho-
PORES OF THE PALATINE TONSILLAR CRYPT
29
cytes pass through these pores from the subepithelial lymphoid tissue into the crypt lumen. Consequently, the tonsillar parenchyma is left open to the crypt and recess lumen through these pores. Although the depth of the pores could not be determined accurately, the pores seem to go through the crypt epithelium all the way to the parenchyma. SUKO (1960) and FALK (1963) reported that lymphocytes immigrate into the crypt epithelium of fetus; lymphocytes were observed in the fetal crypt lumen unassociated with pathological conditions. These findings suggest the presence of pores in the tonsillar crypt in fetus as is shown in the children of this study. Recently, KAWABATA (1978) also observed pores of the tonsillar crypt. He suggested that the pore closes by the insertion of a plug from below and opens by the degeneration of the plug. The crypt epithelium is the place initial contact with invading antigens. The pores of the crypt become the pathway between the tonsillar parenchyma and the crypt lumen possessing extrinsic factors. These pores appear to be important structures for immunological function of the tonsil. The authors are indebted to Drs. Jun-Ichi Suzuki and Tetsuo Ishii (Teikyo University) for their advice and encouragement on this study and to Dr. Robert F. Hink who helped us to prepare the English manuscript.
REFERENCES FALK, P.: Entwicklungsgeschichte, Anatomie, Missbildungen, Physiologie und Pathologie des Rachens (einschliesslich Tonsillen). Berendes, J., Link, R., und Zollner, R., eds. HalsNasen-Ohren HeiIkunde, II/I G Thieme Stuttgart, 1963. FIORETTI, A.: Die Gaumenmandel. G Thieme Verlag Stuttgart, 1961. HAMASHIMA, T.: Immunohistological studies on human palatine tonsils (in Japanese). Jpn. J. Tonsil. 9: 118-128, 1970. KA WABATA, I.: Scanning electron microscopic observations of the human palatine tonsils (in Japanese). Jpn. J. Otol. 79: 733-740, 1976. KAWABATA, I.: The surface structure of human tonsillar crypts-scanning electron microscopic observation (in Japanese). Jpn. J. Tonsil. 17: 204-210, 1978. KAWAGUCHI, E.: Ultrastructure of human palatine tonsil. 1. Electron microscopic studies on tonsillar mucous epithelium (in Japanese). Sapporo Med. J. 31: 144-165, 1967. KODAMA, A. et al.: Scanning electron microscopic study of human tonsillar crypt (in Japanese). Practica Otologica (Kyoto) 70: 479-486, 1977. KODAMA, A. et al.: Scanning electron microscopic study of human pharyngeal tonsil (in Japanese). Practica Otologica (Kyoto) 71: 1017-1023, 1978. LENz, H.: Raumliche Betrachtungen der Tonsilleninnenstruktur mit Hilfe des Rasterelektronenmikroskops. Z. Laryngol. Rhinol. Otol. Ihre Grenzgeb. 51: 262-274, 1972. MURAKAMI, T.: A revised tannin-osmium methods for non-coated scanning electron microscopic specimens. Arch. Histol. Jpn. (Niggata Jpn.) 36: 189-193, 1974. OGINO, Y.: Pathomorphologic studies on the subepithelial basal membrane of the human palatine tonsil (in Japanese). J. Nippon Med. Sch. 18: 1311-1318, 1959. SCHMEDTJE, J. E., and BATTES A. F.: Immunoglobulins and blood vessels in the tonsillar crypt epithelium. Ann. Otol. 82: 359-369, 1973. ST()HR: Uber die Mandeln und deren Entwickelung. Anat. Anz. S. 545: 6, 1891.
A. KODAMA and T. HOSHINO
30
SUKO, H.: Histogenic study of palatine tonsil of human fetus, with special reference on interstitial connective tissue (in Japanese). Jpn. J. 0101.63: 907-924, 1960. TSUCHII, Y.: Electron microscopic studies of the pharyngeal tonsil (in Japanese). Jpn. J. TOllSil. 13: 26-29, 1974. UMETANI, Y.: Postcapillary venule in rabbit tonsil and entry of lymphocytes into its endothelium: a scanning and transmission electron microscopic study. Arch. Hislal. Jpn. 40: 77-94, 1977.
Request reprints from:
Dr. Akira Kodama, Department of Otolaryngology, Teikyo University School of Medicine, Kaga 2-11-1, Itabashi-ku, Tokyo 173, Japan