Plaque-forming cell assays for human B cells

Detection of helper and suppressor T cell lines to soluble antigens using a modified ELISA system

Helper and suppressor activity of T cell lines were investigated using an assay system which is based on measurement by the enzyme-linked immunosorbent assay (ELISA) of the antibody produced in vitro. T cell lines were established from spleens of BALB/c mice immunized with ovalbumin and human serum albumin. The T cells were expanded in culture with irradiated spleen cells and antigen or concanavalin A supernatant. The culture system used for assay of T cell activities contained antigen (Ag)-primed unfractionated spleen cells or Ag-primed B cells. Ag-primed cells and cultured T cells were incubated together with Ag (0.05 ng/ml-100 micrograms/ml) for various times, washed at varying intervals, and supernatants assayed for specific antibody activity by an ELISA adapted for this purpose. A total incubation time of 9 days was required for significant antibody production. Complete reconstitution of the antibody response was observed with Ag-primed B cells and Ag-primed T cells were combined. In one experiment, a helper cell line was shown to restore specific antibody production to approximately 50% of the normal response while a suppressor cell line suppressed antibody production by 90%. A linear response of between 0.2 and 1.4 OD units was observed in the ELISA allowing easy detection of help or suppression. As little as 80 ng of specific antibody could be detected. This technique allows quantitative determination of antibody production for a large number of individual microcultures.