Mediation of cytotoxic functions by classes and subclasses of sheep antibody reactive with cell surface immunoglobulin idiotypic and constant region determinants.

Sheep antibodies, reactive with either the idiotypic or constant region antigenic determinants of the immunoglobulin light chain on guinea-pig L2C leukaemic cells, were separated into IgM and into the two subclasses of IgG, IgG1 and IgG2. Antibody of both IgG subclasses inhibited the migration of L2C cells along plastic surfaces; IgM was only weakly inhibitory. Antibody of class IgM and of subclass IgG1 mediated complement cytotoxicity against the L2C cells whereas only that of subclass IgG2 mediated K-cell cytotoxicity; the effector arms were rabbit complement and sheep peripheral leucocytes, respectively.