Quantitative studies of Fc receptors on bovine leukemic blood lymphocytes: characterization by binding of homologous IgG1 and IgG2.

Receptors for IgG1 and IgG2 (FcR) on peripheral blood lymphocytes from cows with chronic lymphocytic leukemia (CLL) were detected by their ability to bind homologous IgG1 and IgG2 in fluorometric binding assay. Scatchard plots at 4 degrees C demonstrated that IgG1 bound the same number of FcR per cell (3.12 +/- 0.69 X 10(5)) as IgG2 (2.89 +/- 0.69 X 10(5)). The receptors bound IgG2 with an affinity of 4.09 +/- 1.08 X 10(5) 1/M and IgG1 with an affinity of 2.73 +/- 0.55 X 10(5) 1/M, although the difference was not of statistical significance (0.1 greater than P greater than 0.05). Inhibition studies demonstrated that the two ligands could inhibit each other. It might be assumed that FcR for the two subclasses were identical.