Xenogeneic monoclonal antibodies to cell surface antigens of equine lymphocytes.

Monoclonal antibodies to equine lymphocyte antigens were produced, using normal peripheral blood lymphocytes as the immunogen and standard hybridoma techniques. Antibody producing hybridomas were detected by a solid-phase enzyme-linked immunosorbent assay. Antibodies produced by 6 cloned hybrids were characterized further by microlymphocytotoxicity, indirect immunofluorescence, and agglutination assays on peripheral blood lymphocytes, platelets, and erythrocytes. Reaction patterns on leukocytes indicated that these antibodies may recognize at least 3 different cell-surface antigens: (1) an antigen present on most peripheral blood lymphocytes and on platelets, (2) an antigen present on most peripheral blood lymphocytes, but absent from platelets, and (3) an antigen expressed by a major subpopulation of lymphocytes and also present on platelets. This last antigen is polymorphic and is expressed on the lymphocytes of approximately 75% of horses. The distribution of this polymorphic antigen did not correlate with the antigen distribution of any of the defined antigens of the equine major histocompatibility system. None of the 6 monoclonal antibodies reacted with antigens expressed on erythrocytes. These results indicate that monoclonal antibodies may be useful for the identification and characterization of various leukocyte antigens in the horse.