Functional Characterization of Mouse T Lymphocytes with IgM-Fc Receptors: I. Studies on ADCC and Helper Cell Function¹

The function of mouse T lymphocytes with receptors for IgM-Fc was analyzed by using immunofluorescence and a column separation method. The cellular uptake of FITC-IgM was inhibited with unlabeled Fc₅ µ. IgM-FcR⁺ cells were active in ADCC against IgM-sensitized target cells, but not against IgG-coated target cells. The cells mediating ADCC with IgM antibody were shown to be distinct and physically separable from those mediating ADCC with IgG antibody. Helper T lymphocytes for humoral antibody formation in a hapten-carrier system were shown to be IgM-FcR⁺ and Fc-IgG^-.