Cross-reactivity between RSV-induced tumor antigen and B5 MHC alloantigen in the chicken.

Lymphocytes from chickens homozygous (B2B2) at the major histocompatibility complex (MHC) were tested for cytotoxic against five types of target chicken embryo fibroblasts (CEF). Lymphocytes from B2B2 chickens bearing RSV-induced tumors lysed in vitro targets of B2B2 and B5B5 RSV-infected CEF and B5B5 normal CEF, but did not lyse B2B2 and B24B24 normal CEF. Lymphocytes from normal B2B2 chickens did not lyse any of the five types of CEF targets. Alloantisera absorption studies showed that both RSV-infected and uninfected CEF shared alloantigens, in particular B-F alloantigens, with syngeneic erythrocytes. Absorption with B2B2 RSV-infected CEF significantly lowered the titer of B2B2 anti-B5B5 alloantisera. Cross-reactivity between B5 antigen(s) and tumor-associated antigen was suggested and the nature of the cross-reactivity was discussed. It is hypothesized that this cross-reactivity prevents B5B5 chickens from recognizing the RSV-induced tumors as foreign, enhances tumor growth and leads to death of the host.