Comparison of various tests for Fc receptors on different human lymphocyte sub populations.

Six different immune complex test systems for the detection of IgG Fc receptors were applied to the study of various human lymphocyte populations. The extent of binding varied widely according to the system and the cell type employed. Two systems bound preferentially to a high proportion of B lymphocytes from peripheral blood or tonsils, one of which bound with only a very few T cells. In contrast, four other test systems which bound well with the Fc receptors on T lymphocytes gave weaker reactions with Fc receptors on B cells. The reactivity of Fc receptors on null or third population lymphocytes was similar to that of the Fc-positive T cells. Pronase digestion experiments showed a graded selective loss of reactivity with the different Fc reagents. No one system was optimal for all of the lymphocyte populations, although aggregated IgG exhibited the broadest spectrum of reactivity. A pronounced effect of temperature was evident on the binding reactions, and native IgG showed strong binding at 4 degrees C, particularly to the Fc receptors on T cells.