INCREASED PRODUCTION OF INTERLEUKIN-6 BY T-LYMPHOCYTES FROM PATIENTS WITH MULTIPLE-MYELOMA

Alterations in T lymphocyte functions may affect other cellular compon ents of the immune system. Several lymphokines produced by T cells are involved in the proliferation and differentiation of human B lymphocy tes. Alterations in the secretion of these molecules may be implicated in the development of B cell lymphoproliferative diseases. We have in vestigated the production of interleukin-2 (IL-2) and interleukin-6 (I L-6) by T lymphocytes from 14 patients with multiple myeloma (MM) and 16 healthy controls. The phenotypical and functional characteristics o f these T lymphocytes were also studied. The proliferative response to vegetal lectin phytohemagglutinin (PHA) stimulation was decreased in T lymphocytes from MM patients (p < 0.01). This defective proliferativ e response cannot be ascribed to either defective IL-2 production or d iminished receptor expression, since neither of these parameters showe d a significant difference between MM patients and healthy controls (p > 0.05). However, the defective proliferative response of T lymphocyt es from MM patients was reverted by the addition of saturating amounts of exogenous IL-2 (p > 0.05) but not by exogenous IL-6 (p < 0.05). Th e IL-6 production by PHA-stimulated T lymphocytes from the MM patients was significantly higher than in healthy controls (p < 0.01). We conc lude that T lymphocytes from MM patients show a functional alteration with a defective proliferative response to PHA that is reverted by exo genous addition of IL-2. After lectin stimulation, the production of I L-2 by T lymphocytes from those patients was normal, while IL-6 secret ion was increased.