Regulatory T cells in experimental allergic encephalomyelitis. II. T cells functionally antagonistic to encephalitogenic MBP-specific T cells show persistent expression of fasL.

Naive LEW rats and animals that have recovered from active or adoptive EAE contain a subset of T cells that inhibit EAE in secondary recipients and are lytic for MBP-reactive T cell lines in culture. Here we explore various features of these regulatory T cell populations (RTC) with respect to (1) their frequency in animals following immunization with syngeneic MBP-reactive cell lines, (2) their ability to inhibit proliferative responses by MBP-reactive cell lines in culture, (3) their ability to lyse MBP-specific target cells, and especially (4) their prolonged expression of high levels of FasL following activation in culture correlating with their lytic effects on A20, a FasL-sensitive mouse lymphoma cell line. Inhibition studies indicate that mAbs specific for MHC class I and MHC class II molecules inhibit lysis of syngeneic MBP-reactive target T cells, soluble Fas protein shows some inhibition, but none of these agents inhibits the lytic effects of activated RTC on the A20 cell line. Copyright 1999 Wiley-Liss, Inc.