Induction of plasmacytoid and hairy cell features by phorbol esters (TPA) in B-lymphoma cells: attempted correlation with disease activity.

Mononuclear cells concentrated from the blood of 16 non-Hodgkin's lymphoma (NHL) patients in the leukemic phase, were exposed to 10 ng/ml of TPA in an attempt to induce differentiation. Immunoglobulin (Ig) secretion, surface markers (SmIg, GP-70), tartrate resistant acid phosphatase (TRAP) and surface features were followed for up to six days in vitro. TPA induced 'hairy cell' like features in NHL cells as defined by cell morphology, ultrastructure, cell surface markers and the presence of TRAP. Unlike the results obtained in patients with CLL, cells from different patients at the same stage of disease reacted in a similar way. Differences were evident between NHL mononuclear cells obtained from patients in partial remission and active disease when compared with those derived from patients in complete remission. In the former group, NHL cells were maximally induced by TPA to secrete Ig and higher proportions of TRAP positive cells. In addition hairy cell features as seen by light and scanning electron microscopy were also more pronounced. TPA also induced the maximal expression of SmIg and GP-70 in cells derived from patients in this group. Patients with NHL in leukemic phase in complete remission did not express surface membrane GP-70 before or after TPA treatment while SmIg was expressed to some degree before TPA treatment and further induced following treatment with TPA. GP-70 appears to be a more reliable marker for follow-up of NHL patients than any other marker studied here.