Cross-reactivity between human and feline Ia antigens, using a monoclonal antibody HLA-D.m1.

A murine monoclonal antibody HLA-D.m1 produced against human Ia antigens which react with 10% to 30% of human peripheral-blood mononuclear cells was found to react with greater than 90% of feline mononuclear cells. The antigen was not expressed on granulocytes. By direct immunofluorescence, 7% to 41% of feline lymphocytes expressed surface immunoglobulins. In mixed-lymphocyte reaction, the addition of antibody HLA-D.m1 to cultures abolished proliferation. These studies indicate that most feline peripheral-blood mononuclear cells express Ia-like antigens.