Identification of bovine T- and B-lymphocyte subpopulations by immunofluorescence surface marker analysis

A T-cell specific goat anti-bovine thymocyte antiserum was prepared for use in identifying T lymphocytes by an indirect fluorescent antibody (FA) technique. The antiserum was made specific for T lymphocytes through adsorptions with normal bovine RBC, normal serum, and bone marrow cells. It reacted with more than 95% of the thymocytes and less than 5% of the bone marrow cells. By the indirect FA assay, 72.9 +/- 5.7% (SD) of the peripheral blood lymphocytes of adult cows (n = 19) were identified as T lymphocytes. With the previously reported total B-lymphocyte number of 26.9 +/- 4.4%, as determined by a mixture of antiimmunoglobulin (Ig)G, anti-IgA, and anti-IgM, the 2 assays, in conjunction, can thus identify over 95% of the peripheral blood lymphocytes as either T or B lymphocytes. With the use of individual Ig class- and subclass-specific antisera in the direct FA assay, the peripheral blood lymphocytes of adult cows (n = 15) were shown to consist of 8.5 +/- 3.1% IgG1-bearing lymphocytes, 3.5 +/- 2.2% IgG2-bearing lymphocytes, 7.0 +/- 2.4% IgA-bearing lymphocytes, and 13.4 +/- 2.6% IgM-bearing lymphocytes--indicating that although the majority of B lymphocytes possess IgM on their surface, in cattle ther are many B lymphocytes without surface membrane (Sm)IgM, but with only SmIgG1, SmIgG2, or SmIgA.