Human lymphocyte sub-populations and K cells.

Peripheral blood lymphocytes from 19 normal subjects were examined for surface Ig (SIg) and capacity to form rosettes with normal and neuraminidase-treated sheep erythrocytes and with chicken erythrocytes sensitised with IgG antibody. Information on the relationship between the presence of SIg and capacity to form rosettes was obtained by combined tests and depletion experiments. By these means, a population of lymphocytes with Fc receptors, but lacking SIg (mean 14.6%) was defined and shown to correlate closely with cytotoxic activity for antibody-sensitised target cells. Indirect evidence was also obtained that these lymphocytes, which are regarded as the major population of antibody-dependent cytotoxic cells, are capable of forming rosettes with normal and neuraminidase-treated sheep erythrocytes. The nature of these cells is briefly discussed.