Human lamina propria T cells ( LPT) manifest enhanced fas-mediated apoptosis

LPT cells respond poorly to a proliferative stimulus delivered via the TCR/CD3 pathway retaining ability to respond to the CD2 accessory pathway. We evaluated apoptosis in human LPT cells isolated from surgical resected specimen by DTT-EDTA-collagenase treatment followed by gradient separation and immunomagnetic negative selection. Apoptosis was measured by propidium iodide, acridine orange/ethidium bromide staining and Tunel technique fluorescence analysis. We demonstrated that resting LPT cells exhibited an increased rate of apoptosis, when compared to PB T cells, which was enhanced by stimulation of cells via the CD2 pathway but not the TCR/CD3 pathway. In PBT cells neither stimulation via TCR/CD3 nor CD2 pathways increased the rate of apoptosis above baseline levels. The increased apoptosis of CD2-activated cells was mediated via a Fas/Fas ligand interaction. This feature of LPT cells may represent a mechanism of regulating immune responses in the mucosal environment.