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. J. Neurosci. Res. 58:357–366, 1999. © 1999 Wiley‐Liss, Inc.