Differential responsiveness to CD3-Ti vs. CD2-dependent activation of human intestinal T lymphocytes

Human lamina propria lymphocytes were recovered from surgical specimens of unaffected large bowel and compared with peripheral blood lymphocytes (PBL) from the same individual. We investigated their capacities to respond to triggering stimuli delivered by mitogenic monoclonal antibodies directed at the T cell receptor/CD3 complex or, alternatively, the CD2 glycoprotein. In marked contrast to PBL, expression of the interleukin 2/interleukin 2 receptor system was markedly reduced in LPL following activation through the CD3/T cell receptor. Perhaps, more important, responses to CD2 triggering were similar or even stronger in LPL as opposed to PBL. This indicates that the CD2-dependent alternative pathway of T cell activation might serve a functional role in local immunity in the gut.