Analysis by a plaque assay of IgG- or IgM- dependent cytolytic lymphocytes in human blood.

Abstract

When monolayers of bovine erythrocytes (Eb) were exposed to purified human blood lymphocytes and IgG [immunoglobulin G] or IgM fractions of rabbit anti-Eb serum, clear zones (plaques) appeared where Eb were lysed by antibody-dependent effector cells (K cells). IgG-dependent plaque formation was complete by 20 h of incubation, while the IgM-dependent reaction required 40 h. The estimated minimal numbers of plaque forming cells (PFC) were 5.6% (IgG) and 2.0% (IgM) of the added lymphocytes. Inhibition experiments with human IgG or IgM indicated that different Ig receptors on the effector cells were involved in the 2 system. In the IgG, .apprx.50% of the PFC had complement receptors and .apprx.30% receptors for Helix pomatia A hemagglutinin (HP). In the IgM system, < 10% of the PFC had complement receptors, while .apprx.60% had HP receptors. A subset of human T [thymus-derived] cells apparently had IgM-dependent K-cell potential. These cells are different from the majority of the IgG-dependent K cells.