Polyclonal antibody secretion induced in human mixed lymphocyte cultures.

In mixed leucocyte culture (MLC), using human spleen cells or thoracic duct lymphocytes, antibody secretion was induced, measured as plaque-forming cells (PFC) in a haemolysis-in-gel assay with fluorescein isothiocyanate (FITC)-coupled sheep erythrocytes (SRBC) as targets. Peak antibody secretion was seen on day 5. Using protein-A-coupled SRBC as targets and developing antisera, antibody secretion in MLC was found to be of IgM, IgG and IgA type. There was no correlation between the number of PFC against FITC-SRBC in MLC and DNA synthesis. Supernatants from MLC failed to induce antibody secretion.