Antibody-dependent, cell-mediated cytotoxicity against human red blood cells: correlation of effector cell type with enzymatic alteration of the target cell surface.

Target cell factors, which contribute to the determination of the effector cell type in an antibody-dependent, cell-mediated cytotoxicity system were studied. Human red blood cells (RBC) were treated with papain and investigated by transmission and scanning electron microscopy (TEM and SEM). Both untreated (native) and treated 0 Rh+ RBC were labeled with 51Cr, sensitized with anti-D immunoglobulin and incubated with unfractionated autologous peripheral blood mononuclear cells. With native RBC, immune lysis was proportional to the number of phagocytes: enrichment of effectors in phagocytes increased lysis, while depletion of phagocytes from effectors decreased lysis. Following papain treatment of target RBC, lysis by unfractionated mononuclear effectors was markedly augmented; since this effect was not diminished by decrease of phagocytes to less than 2%, the augmented lysis was not due to the number of phagocytic effectors. TEM and SEM of enzyme-treated RBC showed spherocytosis with varying degrees of crenation and blurring and irregularities of the cellular membranes. The results suggest that papain-induced alterations in the target RBC rendered them susceptible to lysis by interaction between anti-D antibody and peripheral blood lymphocytes.