G. W. Hoffmann,"On I-J, a network centre pole and AIDS. In "The Semiotics of Cellular Communication in the Immune System" (E. Sercarz, F. Celada, N. A. Mitchison and T. Tada, Eds.) Springer-Verlag, New York, 1988, pp. 257-271.

I-J is the most famous paradox of modern immunology. An entity that had been shown to exist by extensive genetic evidence, and which evidently plays a key role in immunoregulation, was mapped very precisely to a small region of the MHC called I-J. When however molecular biologists tried to obtain the gene for I-J, they discovered it was not to be found at the expected location. Mice that are believed to differ only in their I-J phenotype can be cross-immunized and then produce anti-I-J antibodies. These antibodies react with antigen-specific suppressor T cell factors and suppressor T cells. Because suppressor T cells played an important role in network theory, I-J has implications for the validation of network theory. It was therefore of utmost importance to resolve this paradox. The resolution led to a model for AIDS pathogenesis, in which HIV triggers autoimmunity.It is suggested in this model that foreign lymphocytes are a cofactor in AIDS pathogenesis, since the immune response to these cells includes a response that could synergize with the immune response to HIV.