Regulation of allotype expression in heterozygous rabbits. I. Concomitant modulation of cell surface allotypes on peripheral blood lymphocytes from b4b6 rabbits.

Treatment of b4b6 rabbit peripheral blood lymphocytes with b5b5 anti-b4 antibodies at 4 degrees resulted in the modulation (disappearance) ob b4 and b6 cell surface allotype after subsequent incubation in serum-free medium for 1 h at 37 degrees. A clear dose dependence on the sensitizing anti-b4 antibody was observed. Similarly, b5b5 anti-b6 treatment demonstrated a dose dependence for b6 modulation and a threshold dose effect for b4 comodulation. Cells which formed rosettes with anti-b4-coupled SRBC (anti-b4 direct antiglobulin (DAG) rosettes) also demonstrated concomitant modulation of b4 and b6 allotype when incubated at 37 degrees. When cells formed anti-b6 DAG rosettes, subsequent b6 modulation could also be demonstrated, but no b4 comodulation occurred. Concomitant modulation did not occur when cells were incubated with anti-allotype antibodies at 37 degrees. Blocking studies disclosed that the two allotypes are not contiguous in the membrane since uptake of one antiallotype antibody did not block the uptake of another at 4 degrees. We therefore propose that concomitant modulation might occur during a process similar to patch formation.