Suppression of immunoglobulin production by germinal centre HNK-1+ CD3+ cells.

Germinal centre T cells co-expressing HNK-1 antigen have little lytic activity against NK targets (K562 cells). In order to determine whether these cells regulate B cell function, they were purified from human tonsils by panning on anti-HNK-1 antibody coated Petri dishes and co-cultured with autologous and allogeneic tonsillar T and B cells in the presence of pokeweed mitogen. At the end of 7 days of culture, supernatants were assayed for immunoglobulin concentration by ELISA. A dose-dependent suppression of both IgG and IgM production was demonstrated at ratios from 1:125 to 1:16 of HNK-1+ cells to B cells, but enhancement was observed at very low ratios (less than 1:500) or ratios exceeding 1:16 in some tonsil preparations. Similar results were obtained with peripheral blood HNK-1+ cells but without enhancement in some cases at the extremes of HNK-1+ cells to B cell ratios. The suppression was not MHC-restricted. These preliminary experiments indicate that germinal centre HNK-1+ cells may be intrafollicular suppressor cells.