Cytotoxicity Mediated by Human Lymphocyte-Dependent Antibody in a Rapid Assay with Adherent Target Cells

Abstract

Abstract A rapid in vitro assay for lymphocyte-dependent antibody (LDA)-mediated cytotoxicity against adherent target cells has been characterized. Adherent HeLa and human melanoma cell lines were labeled with 51Cr, coated with sera from patients who had received multiple whole blood transfusions, and incubated for 4 hr with human peripheral blood lymphocytes from normal donors. Significant lysis was detected as early as 20 min after incubation with rapid progression in the reaction during the next several hours. Morphologically, the early phase of the reaction was characterized by adherence of lymphocytes to LDA-coated cells. Cytotoxic activity was proportional to LDA concentration, attacking cell concentration, and incubation time. LDA-mediated cytotoxicity was blocked by anti-IgG, supporting the concept that this factor is an antibody. LDA-coated target cells were killed by lymphocytes but not by adherent peripheral blood cells or tissue culture lymphoid cells. Conventional complement did not play a role in target cell destruction because carrageenan, a C1 inhibitor, was included in the reactions and serum samples were heat-inactivated before use. This rapid in vitro assay will prove useful in distinguishing between cytotoxicity resulting from lymphocyte-dependent antibody and other types of cell-mediated cytotoxicity.