Identification of isotypes and allotypes of bovine immunoglobulin M with monoclonal antibodies.

Epitopes specific for IgM on peripheral blood lymphocytes from 47 cattle were examined with three class-specific monoclonal antibodies, IL-A30, IL-A50 and B5/4. In all 47 animals tested, mAb IL-A30 detected a similar percentage of peripheral blood lymphocytes as a mAb that recognizes all immunoglobulin classes. However, in some animals mAbs IL-A50 and B5/4 detected a lower percentage of B cells compared with IL-A30 or the mAb against total Ig. They both reacted with a proportion of the serum IgM from these animals, while IL-A30 reacted with all serum IgM. Therefore, it is probable that mAb-A30 recognizes an IgM isotypic determinant and mAbs IL-A50 and B5/4 recognize different IgM allotypic determinants. Using mAb IL-A30 it was found that the percentage of peripheral blood IgM+ lymphocytes varied widely between healthy cattle (4-31%) but remained constant, with only minor variations, within individual animals.