T-CELLS OF THE HUMAN INTESTINAL LAMINA PROPRIA ARE HIGH PRODUCERS OF INTERLEUKIN-10

Background and aim-Some of the recently observed functional features c haracteristic of immunocompetent cells residing in the human intestina l lamina propria could be mediated by interleukin-10 (IL-10). To inves tigate the role of IL-10 in the human intestinal mucosa, the regulatio n of IL-10 production by lamina propria T lymphocytes (LPL-T) was dete rmined and compared with that of peripheral blood T lymphocytes (PBL-T ). Methods-Following activation by using different stimuli, IL-10 rele ase by LPL-T and PBL-T into the supernatant was measured by enzyme lin ked immunosorbent assay (ELISA). In parallel, cell growth was determin ed by [H-3]-thymidine incorporation. Results-Neither LPL-T nor PBL-T r elease IL-10 constitutively. Triggering through CD2 or the T cell rece ptor (TCR)/CD3 complex in the presence of autologous monocytes induces significantly greater IL-10 secretion by LPL-T than by PBL-T. Engagem ent of the CD45 receptor enhances IL-10 release and proliferation of C D2 triggered CD45RO+ PBL-T. In contrast, it reduces CD2 induced IL-10 production by LPL-T without altering cell growth significantly. Conclu sions Activated LPL-T release relatively high amounts of IL-10. Enhanc ed IL-10 production by activated LPL-T, in comparison with activated P BL-T, is not only related to the presence of a higher proportion of CD 45RO+ T cells in the intestinal lamina propria, but is also caused by increased sensitivity of LPL-T to CD2 co-stimulation. The differential responsiveness of LPL-T, compared with PBL-T, to CD45 engagement demo nstrates that CD45 could be involved in the altered CD2 reactivity of LPL-T.