Anti-alpha chain monoclonal antibodies of equine MHC class-II antigens: applications to equine infectious anaemia.

This paper describes the characteristics of a monoclonal antibody (mAb), 6B11C3, that recognises most equine monocytic cells, as well as B- and T-lymphocytes. The T CD4+ and T CD8+ of this latter population are also stained by the 6B11C3 mAb. On the basis of the distribution of membrane antigens on these cell populations, and of immunohistochemistry results, this mAb appears to be an anti-equine class-II major histocompatibility complex (MHC) antigen. In horses, the hyperexpression of the MHC class-II antigen on T cells is an indication of activated lymphocytes. A decrease in the percentage of lymphocytes stained by 6B11C3 was observed in horses with persistent equine infectious anaemia.