The anti-human CD21 antibody, BU33, identifies equine B cells.

The number of antibodies for identifying equine B cells is small and the number that react with well-defined epitopes even smaller. The monoclonal antibody, BU33, which is directed against human CD21 (Complement Receptor 2; CR2) was shown to identify (1) follicular lymphocytes in the lymph nodes and spleen of three horses, and (2) a mean of 18 +/- 6% (SEM) of peripheral blood lymphocytes from 10 horses. These findings indicate that the antibody identifies equine B cells and possibly equine CR2 or a related molecule. This study adds to the reagents available for equine research and diagnostic pathology.