In vitro target cell lysis mediated by normal human lymphocytes (K cells) or monocytes

Guinea pig IgG1 or IgG2 anti-dinitrophenyl (DNP) Antibody preparations were used for induction of target cell lysis by normal human lymphocytes (K cells) or monocytes. Target cells were DNP-coated 51Cr-labeled chicken erythrocytes. Antibody concentrations were assayed by an ammonium sulphate precipitation technique. When antiserum was obtained by immunization with the antigen in Freund's complete adjuvant (FCA), IgG2 antibodies predominated and were significantly more efficient inducers of K-cell-mediated lysis than IgG1 antibodies. The lowest activity in K-cell-mediated lysis was seen with IgG1 from antiserum obtained by immunization with antigen in Freund's incomplete adjuvant. When these antibody fractions were tested in monocyte-mediated erythrolysis, the two IgG1 fractions were as active as the IgG2 antibodies raised with antigen incorporated in FCA. The results suggest that the Fc receptors of mature human blood monocytes are different from those on the effector cells in the K-cell preparations.