The sequence of a feline class I pseudogene and its comparison with class I genes from other species is presented. The gene isolated is a pseudogene because of the presence of four stop codons and two frame shift mutations in the first- and second-domain encoding exons, as well as a mutation in a splice acceptor site in the third intron. By sequence comparison with the other class I sequences determined to date, the FLA pseudogene is most closely related to the HLA-A locus products (88% nucleotide identity.

Although retinal S-antigen can induce experimental auto-immune uveitis in various animal species including primates, its role in clinical uveitis is not exactly known. More detailed knowledge on the immunoreactivity of human S-antigen might be of importance, since bovine S-antigen has been shown to carry both uveitogenic and non-uveitogenic epitopes. The number of immunoreactive epitopes on purified human S-antigen was therefore investigated in an inhibition ELISA with the use of a panel of four polyclonal and two monoclonal immune reagents. Assessment of their capacity to compete with each other for binding to the antigen resulted in complete, partial or no inhibition in the various combinations tested. Rabbit and rat anti-S-antigen immunoglobulins inhibited each other partially (up to 60%), from which the existence of at least three (groups of) epitopes was derived. Two monoclonal antibodies, of mouse (PDS-1) and rat (S.2.4C5) origin, did not inhibit each other, and thus defined two separate epitopes on human S-antigen. These epitopes belong to the set recognized by both rabbit and rat anti-S-antigen immunoglobulins since both mono-clonals could be inhibited by rabbit and by rat antibodies. Epitopes detected by two mouse antisera also appeared to belong to this set. Thus, the existence of at least four immunoreactive sites on human S-antigen could be demonstrated.