Multiple myeloma: evidence that light chains play an immunoregulatory role in B-cell regulation.

Supernatants from human lymphoblastoid and plasma cell lines were added to cultures of normal cells stimulated with pokeweed mitogen (PWM) with the aim of providing an in vitro model for light chain isotype suppression (LCIS). Supernatants from the kappa-secreting cell line LICR-LON-HMY2 were specifically able to block the secretion of kappa-associated immunoglobulin and supernatants from the lambda-secreting cell line U266 were specifically able to block the secretion of lambda-associated immunoglobulin without any effect on the secretion of the other light chain isotype. Supernatant from a human leukemia line, HL60, did not block either kappa or lambda immunoglobulin secretion. Purging studies where kappa or lambda light chains were removed from supernatants of these cell lines suggest that this is a direct effect of light chain and not due to any other nonspecific inhibitory material which may be present.