CD43 potentiates CD3-induced proliferation of murine intestinal intraepithelial lymphocytes

The involvement of CD43 in cell proliferation of murine intestinal intraepi thelial lymphocytes (IEL) has been studied in in vitro CD3-stimulated cell cultures. In the presence of either IL-2 or IL-15, CD3 stimulation of IEL r esulted in low levels of proliferation as measured by thymidine incorporati on, whereas no proliferation occurred upon CD3 stimulation in the absence o f cytokines. The combination of both cytokines to IEL cultures synergistica lly enhanced CD3-induced proliferation by approximately threefold that of c ultures supplemented with either cytokine alone. Most importantly, however, proliferation of IEL was significantly greater when CD3 stimulation occurr ed in conjunction with CD43 triggering, indicating that CD43 functions as a coactivational signal for murine IEL. These findings indicate that a spect rum of potential proliferative responses exist among murine IEL depending o n the types and combinations of signals received, and that because under no rmal conditions murine IEL are largely devoid of CD28 expression, a classic al T-cell coactivational molecule, the capacity for high-level IEL prolifer ation may reside with CD43.