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Xenopus laevis splenocyte receptors for immunoglobulins
Vol.
ii, No. 2
ISDCI ECTOTHERM SYMPOSIUM
447
THYMIC SECRETORY CELLS OF POIKILOTHERMIC VERTEBRATES Janusz Bigaj I and Barbara P~[ytycz Z l l n s t i t u t e of Applied Zoology, Academy of Agriculture, Krakow; ZDepartment of C o m p a r a t i v e Anatomy, Jagellonian University, Krakow, Poland. The main p r i m a r y lymphoid organ, the thymus, is absent in cyclostomes, while it is present in jawed poikilothermic v e r t e b r a t e s , i.e., fish, amphibians, and reptiles. As in e n d o t h e r m i c v e r t e b r a t e s , i.e., birds and mammals, it consists of lymphoid cells within an epithelial framework, as well as myoid, interdigitating, and s e c r e t o r y cells (e.g. Bigaj, J. and P~[ytycz, B., Fol. Histochem. C y t o c h e m . ZZ:63, 1984). Some s e c r e t o r y cells contain clear vesicles with f l o c c u l e n t or amorphous material. Their u i t r a s t r u c t u r a l appearance indicates that t h e y are p e p t i d e - s e c r e t i n g cells of the APUD series. Other epithelial s e c r e t o r y cells are variable in a p p e a r a n c e and contain more or less densely stained cytoplasmic granules of various sizes. Their u l t r a s t r u c t u r a l f e a t u r e s indicate that they are mucous-secreting cells. In favourably o r i e n t a t e d m a t e r i a l it could he seen that epithelia/ s e c r e t o r y cells are organized into cystic s t r u c t u r e s which may be the s e c r e t o r y units of the thymus gland. During winter hibernation the thymuses of frogs, toads, and snakes contain an unusually abundant population of s e c r e t o r y units. S e c r e t o r y m a t e r i a l is released at the beginning of active life. The population of cells filled with s e c r e t o r y granules is significantly diminished during the a c t i v e life of these animals (P~[ytycz, B. and Bigaj, J., Thumus, 5:3Z7, 1983). T h e r e f o r e , hibernating species can serve as a very convenient m a t e r i a l for studying the thymic s e c r e t o r y cells. XENOPUS
LAEVIS SPLENOCYTE
RECEPTORS
FOR IMMUNOGLOBULINS
V. Coosemans and L Hadji-Azimi Station de Zoologie Experimentale, Geneva, Switzerland The existence of a m e m b r a n e - a s s o c i a t e d r e c e p t o r for Ig is d e m o n s t r a t e d on a large p e r c e n t a g e of Xenopus splenocytes. The r e c e p t o r was d e t e c t e d by fluorescent staining in which the spleen cells were incubated with h e a t - a g g r e g a t e d FITC labelled IgM or with FITC or TRITC labelled a n t i g e n - c o m p l e x e d IgY antibodies. Results showed that Z8.4% (SD:5.1) and 5.3% (SD:Z.Z) of the ceUs bear r e c e p t o r s for IgY and r e c e p t o r s for IgM respectively. The identity of the cells bearing r e c e p t o r s for IgY was established by double f l u o r e s c e n t staining of surface Ig and Ig r e c e p t o r s . All Xenopus splenic B lymphocytes bearing slg bind also a n t i g e n - c o m p l e x e d IgY, while a small p e r c e n t a g e of splenocytes c a r r y on their surface, r e c e p t o r s for IgY alone. The i d e n t i t y of these l a t t e r cells and that of cells bearing r e c e p t o r s for IgM remains to be established. In order to d e t e r m i n e the Ig f r a g m e n t responsible for binding to the r e c e p t o r s , Xenopus IgM and IgY were digested by trypsin and their r e s p e c t i v e f r a g m e n t s were s e p a r a t e d by c h r o m a t o g r a p h y and immunoabsorption. Two f r a g m e n t s of Fc6u and Fabu and t h r e e antigen-binding f r a g m e n t s of F a b u were obtained a f t e r IgM and IgY digestion, respectively. No F c f r a g m e n t could be d e t e c t e d a f t e r t y p t i c digestion of IgY. Binding to the splenocytes could be shown with h e a t - a g g r e g a t e d Fc6u, but not with a g g r e g a t e s of Fabu nor with a n t i g e n - c o m p l e x e d Fab]J. These results indicate t h a t the binding of both Ig's and strongly suggest t h a t the m e m b r a n e r e c e p t o r s d e t e c t e d on Xenopus splenocytes are homologous to the well known Fc r e c e p t o r described in mammals.
ii, No. 2
ISDCI ECTOTHERM SYMPOSIUM
447
THYMIC SECRETORY CELLS OF POIKILOTHERMIC VERTEBRATES Janusz Bigaj I and Barbara P~[ytycz Z l l n s t i t u t e of Applied Zoology, Academy of Agriculture, Krakow; ZDepartment of C o m p a r a t i v e Anatomy, Jagellonian University, Krakow, Poland. The main p r i m a r y lymphoid organ, the thymus, is absent in cyclostomes, while it is present in jawed poikilothermic v e r t e b r a t e s , i.e., fish, amphibians, and reptiles. As in e n d o t h e r m i c v e r t e b r a t e s , i.e., birds and mammals, it consists of lymphoid cells within an epithelial framework, as well as myoid, interdigitating, and s e c r e t o r y cells (e.g. Bigaj, J. and P~[ytycz, B., Fol. Histochem. C y t o c h e m . ZZ:63, 1984). Some s e c r e t o r y cells contain clear vesicles with f l o c c u l e n t or amorphous material. Their u i t r a s t r u c t u r a l appearance indicates that t h e y are p e p t i d e - s e c r e t i n g cells of the APUD series. Other epithelial s e c r e t o r y cells are variable in a p p e a r a n c e and contain more or less densely stained cytoplasmic granules of various sizes. Their u l t r a s t r u c t u r a l f e a t u r e s indicate that they are mucous-secreting cells. In favourably o r i e n t a t e d m a t e r i a l it could he seen that epithelia/ s e c r e t o r y cells are organized into cystic s t r u c t u r e s which may be the s e c r e t o r y units of the thymus gland. During winter hibernation the thymuses of frogs, toads, and snakes contain an unusually abundant population of s e c r e t o r y units. S e c r e t o r y m a t e r i a l is released at the beginning of active life. The population of cells filled with s e c r e t o r y granules is significantly diminished during the a c t i v e life of these animals (P~[ytycz, B. and Bigaj, J., Thumus, 5:3Z7, 1983). T h e r e f o r e , hibernating species can serve as a very convenient m a t e r i a l for studying the thymic s e c r e t o r y cells. XENOPUS
LAEVIS SPLENOCYTE
RECEPTORS
FOR IMMUNOGLOBULINS
V. Coosemans and L Hadji-Azimi Station de Zoologie Experimentale, Geneva, Switzerland The existence of a m e m b r a n e - a s s o c i a t e d r e c e p t o r for Ig is d e m o n s t r a t e d on a large p e r c e n t a g e of Xenopus splenocytes. The r e c e p t o r was d e t e c t e d by fluorescent staining in which the spleen cells were incubated with h e a t - a g g r e g a t e d FITC labelled IgM or with FITC or TRITC labelled a n t i g e n - c o m p l e x e d IgY antibodies. Results showed that Z8.4% (SD:5.1) and 5.3% (SD:Z.Z) of the ceUs bear r e c e p t o r s for IgY and r e c e p t o r s for IgM respectively. The identity of the cells bearing r e c e p t o r s for IgY was established by double f l u o r e s c e n t staining of surface Ig and Ig r e c e p t o r s . All Xenopus splenic B lymphocytes bearing slg bind also a n t i g e n - c o m p l e x e d IgY, while a small p e r c e n t a g e of splenocytes c a r r y on their surface, r e c e p t o r s for IgY alone. The i d e n t i t y of these l a t t e r cells and that of cells bearing r e c e p t o r s for IgM remains to be established. In order to d e t e r m i n e the Ig f r a g m e n t responsible for binding to the r e c e p t o r s , Xenopus IgM and IgY were digested by trypsin and their r e s p e c t i v e f r a g m e n t s were s e p a r a t e d by c h r o m a t o g r a p h y and immunoabsorption. Two f r a g m e n t s of Fc6u and Fabu and t h r e e antigen-binding f r a g m e n t s of F a b u were obtained a f t e r IgM and IgY digestion, respectively. No F c f r a g m e n t could be d e t e c t e d a f t e r t y p t i c digestion of IgY. Binding to the splenocytes could be shown with h e a t - a g g r e g a t e d Fc6u, but not with a g g r e g a t e s of Fabu nor with a n t i g e n - c o m p l e x e d Fab]J. These results indicate t h a t the binding of both Ig's and strongly suggest t h a t the m e m b r a n e r e c e p t o r s d e t e c t e d on Xenopus splenocytes are homologous to the well known Fc r e c e p t o r described in mammals.