- Email: [email protected]
Schistosome-snail immunological compatibility: Shared antigens in the model Trichobilharzia ocellata - lymnaea stagnalis
172
IMMUNORECOGNITION
NON-SELF RECOGNITION IN L I N E U S : ALLOGRAFTS SUCCEED OF THE MONOMORPHISM OF THE MAJOR HISTOCOMPATIBILITY J. Bierne, Universite d e C h a m p a g n e , 5 1 0 6 2 Reims, France. In nemertines of the g e n u s L i n e u s , s y n g e n e i c a n d a]]ogeneic
Vol.
9, No.
i
BECAUSE GENES. grafts s u c c e e d
b u t x e n o g e n e i c g r a f t s f a i l . S i n c e t h e major h i s t o c o m p a t i b i l i t y g e n e s (MH g e n e s ) a r e t h o s e w h o s e p r o d u c t s , a n t i g e n s , a r e c o m p e t e n t to e n g e n d e r e f f e c t i v e t r a n s p l a n t a t i o n r e a c t i o n s , t h e s u c c e s s of t r a n s p l a n t s e x c h a n g e d b e t w e e n w o r m s of t h e s a m e s p e c i e s o r t h e i r f a i l u r e in i n t e r s p e c i f i c p a i r s a r e w h a t is e x p e c t e d of a t r a i t d e t e r m i n e d b y MH g e n e s e n c o d i n g f o r t r a n s p l a n t a t i o n x e n o a n t i g e n s ( i . e . , m o l e c u l e s c a p a b l e of e l i c i t i n g an immune r e s p o n s e o n l y w h e n t r a n s f e r e d b e t w e e n s p e c i e s ) . In e a c h L i n e u s s p e c i e s , MH loci e x i s t b u t MH g e n e s a r e m o n o m o r p h i c , t h u s t h e y i n d u c e no a l l o g r a f t r e a c t i o n s . T h i s s u r p r i s i n g f i n d i n g - a b s e n c e of g e n e p o l y m o r p h i s m - a g r e e s w i t h d a t a f r o m s t u d i e s of t h e e l e e t r o p h o r e t i c m o b i l i t y of s i x e n z y m e s in three Lineus species. Intraspecific monomorphism versus interspecific d i v e r s i t y of g e n e p r o d u c t s is i n d e e d t h e s t r i k i n g o b s e r v a t i o n made in L. r u b e r , L. v i r i d i s a n d L. s a n g u i n e u s f o r 6 - P G D H , SOD, MDH, PGM, GOT a n d AP (1) . If a l l o g r a f t r e j e c t i o n s a r e u s u a l in m e t a z o a n s , n e m e r t i n e s of t h e g e n u s L i n e u s a r e an e x c e p t i o n to t h e r u l e b e c a u s e of t h e m o n o m o r p h i s m of t h e i r MH g e n e s . A l t h o u g h s u c h a c o m p l e t e a b s e n c e of a l l e l i c d i v e r s i t y of MH g e n e s w i t h i n s p e c i e s is s i n g u l a r , we c a n p r o f i t a b l y r e l a t e a b s e n c e to t h e u n u s u a l m o n o m o r p h i s m of c l a s s - I MH g e n e s in t h e S y r i a n h a m s t e r ( 2 ) . (1) Williams, K . A . , S k i b i n s k i , D . O . F . , a n d G i b s o n R. ( 1 9 8 3 ) . J . E x p . Mar. B i o l . E c o l . 6 6 , 2 0 7 - 2 1 1 . (2) S t r e i l e i n , J . W . a n d D u n c a n , W . R . (1983) T r a n s p l a n t . P r o c . 1 5 , 1 5 4 0 - 1 5 4 5 .
SCHISTOSOME-SNAIL
TRICHOBILHARZIA
IMMUNOLOGICAL
COMPATIBILITY:
S H A R E D A N T I G E N S IN THE M O D E L W.P.W. van der Knaap, E.A. Faculty of Medicine, Free University, P.O.Box 7161,
OCELLATA - LYMNAEA S2AGNALIS.
Meuleman and J.J. Mellink, Amsterdam, The Netherlands. Parasites survive in their host only if they are immunologically compatible. A way to achieve such compatibility is sharing of antigens: the parasite may evade i ~ u n o r e c o g n i t i o n by covering itself with host(-like) material. The schistosome Trichobilharzia ocelL~ta is searched for substances with antigenic similarities to molecules of its intermediate host, the pond snail Lymnaea stagnalis Using antisera to snail haemolymph constituents and to snail tissue, the para. site was stained immunocytochemically (PAP-method) in 5 successive phases of its development. The two types of antisera yielded similar results. Miracidia, a l a r val stage of the parasite that penetrates the snail host, possess snail-like molecules. This may indicate that, in its establishment phase, the parasite uses molecular mimicry to evade iramunorecognition. Once within the snail, the miracidium sheds its epithelial plates and transforms into a mother sporocyst. Initial. ly, some of the snail-like material is still present, but soon it is beyond detection. Daughter sporocysts, which develop in the mother sporocysts, mature, leave the mother sporocyst, migrate and settle, mainly in the digestive gland area of the snail. No snail(-like) material was detected on daughter sporocysts. The next larval generation, the cercariae, develop and mature in the daughter sporocysts, from which they emerge, find their way out of the snail to infect a definitive host (water fowl). Snail(-like) substances were not found on the surface of the cercariae when still within the daughter sporocyst. Once the cercariae have emerged and have come into contact with snail haemolymph, they are covered by a layer of snail material. Possibly, this layer protects the cercaria from recognition and subsequent attack by the snail's inu~une system.
IMMUNORECOGNITION
NON-SELF RECOGNITION IN L I N E U S : ALLOGRAFTS SUCCEED OF THE MONOMORPHISM OF THE MAJOR HISTOCOMPATIBILITY J. Bierne, Universite d e C h a m p a g n e , 5 1 0 6 2 Reims, France. In nemertines of the g e n u s L i n e u s , s y n g e n e i c a n d a]]ogeneic
Vol.
9, No.
i
BECAUSE GENES. grafts s u c c e e d
b u t x e n o g e n e i c g r a f t s f a i l . S i n c e t h e major h i s t o c o m p a t i b i l i t y g e n e s (MH g e n e s ) a r e t h o s e w h o s e p r o d u c t s , a n t i g e n s , a r e c o m p e t e n t to e n g e n d e r e f f e c t i v e t r a n s p l a n t a t i o n r e a c t i o n s , t h e s u c c e s s of t r a n s p l a n t s e x c h a n g e d b e t w e e n w o r m s of t h e s a m e s p e c i e s o r t h e i r f a i l u r e in i n t e r s p e c i f i c p a i r s a r e w h a t is e x p e c t e d of a t r a i t d e t e r m i n e d b y MH g e n e s e n c o d i n g f o r t r a n s p l a n t a t i o n x e n o a n t i g e n s ( i . e . , m o l e c u l e s c a p a b l e of e l i c i t i n g an immune r e s p o n s e o n l y w h e n t r a n s f e r e d b e t w e e n s p e c i e s ) . In e a c h L i n e u s s p e c i e s , MH loci e x i s t b u t MH g e n e s a r e m o n o m o r p h i c , t h u s t h e y i n d u c e no a l l o g r a f t r e a c t i o n s . T h i s s u r p r i s i n g f i n d i n g - a b s e n c e of g e n e p o l y m o r p h i s m - a g r e e s w i t h d a t a f r o m s t u d i e s of t h e e l e e t r o p h o r e t i c m o b i l i t y of s i x e n z y m e s in three Lineus species. Intraspecific monomorphism versus interspecific d i v e r s i t y of g e n e p r o d u c t s is i n d e e d t h e s t r i k i n g o b s e r v a t i o n made in L. r u b e r , L. v i r i d i s a n d L. s a n g u i n e u s f o r 6 - P G D H , SOD, MDH, PGM, GOT a n d AP (1) . If a l l o g r a f t r e j e c t i o n s a r e u s u a l in m e t a z o a n s , n e m e r t i n e s of t h e g e n u s L i n e u s a r e an e x c e p t i o n to t h e r u l e b e c a u s e of t h e m o n o m o r p h i s m of t h e i r MH g e n e s . A l t h o u g h s u c h a c o m p l e t e a b s e n c e of a l l e l i c d i v e r s i t y of MH g e n e s w i t h i n s p e c i e s is s i n g u l a r , we c a n p r o f i t a b l y r e l a t e a b s e n c e to t h e u n u s u a l m o n o m o r p h i s m of c l a s s - I MH g e n e s in t h e S y r i a n h a m s t e r ( 2 ) . (1) Williams, K . A . , S k i b i n s k i , D . O . F . , a n d G i b s o n R. ( 1 9 8 3 ) . J . E x p . Mar. B i o l . E c o l . 6 6 , 2 0 7 - 2 1 1 . (2) S t r e i l e i n , J . W . a n d D u n c a n , W . R . (1983) T r a n s p l a n t . P r o c . 1 5 , 1 5 4 0 - 1 5 4 5 .
SCHISTOSOME-SNAIL
TRICHOBILHARZIA
IMMUNOLOGICAL
COMPATIBILITY:
S H A R E D A N T I G E N S IN THE M O D E L W.P.W. van der Knaap, E.A. Faculty of Medicine, Free University, P.O.Box 7161,
OCELLATA - LYMNAEA S2AGNALIS.
Meuleman and J.J. Mellink, Amsterdam, The Netherlands. Parasites survive in their host only if they are immunologically compatible. A way to achieve such compatibility is sharing of antigens: the parasite may evade i ~ u n o r e c o g n i t i o n by covering itself with host(-like) material. The schistosome Trichobilharzia ocelL~ta is searched for substances with antigenic similarities to molecules of its intermediate host, the pond snail Lymnaea stagnalis Using antisera to snail haemolymph constituents and to snail tissue, the para. site was stained immunocytochemically (PAP-method) in 5 successive phases of its development. The two types of antisera yielded similar results. Miracidia, a l a r val stage of the parasite that penetrates the snail host, possess snail-like molecules. This may indicate that, in its establishment phase, the parasite uses molecular mimicry to evade iramunorecognition. Once within the snail, the miracidium sheds its epithelial plates and transforms into a mother sporocyst. Initial. ly, some of the snail-like material is still present, but soon it is beyond detection. Daughter sporocysts, which develop in the mother sporocysts, mature, leave the mother sporocyst, migrate and settle, mainly in the digestive gland area of the snail. No snail(-like) material was detected on daughter sporocysts. The next larval generation, the cercariae, develop and mature in the daughter sporocysts, from which they emerge, find their way out of the snail to infect a definitive host (water fowl). Snail(-like) substances were not found on the surface of the cercariae when still within the daughter sporocyst. Once the cercariae have emerged and have come into contact with snail haemolymph, they are covered by a layer of snail material. Possibly, this layer protects the cercaria from recognition and subsequent attack by the snail's inu~une system.