IMMUNE REGULATION BY SIALOGLYCOCONJUGATE-BINDINGLECTINS: T cell costimulation by L-selectin

摘要

L-selectin that binds 6-sulfo sLe~X mediates the first step in the leukocyte-endothelial cell interaction as a rolling receptor on T cells. Furthermore, it is suggested that L-selectin plays a fundamental role as a signal transduction molecule. Here,we show the costimulatory activity of L-selectin in murine T cells using anti L-selectin monoclonal antibody, MEL14. Purified T cells proliferated in response to immobilized anti-CD3 antibody alone, and immobilized MEL14 enhanced this proliferation. Next, we assessed whether signaling via L-selectin can rescue unresponsiveness of T cells. MEL14 significantly enhanced the proliferation of responding T cells obtained from PBS-injected mice, however, unresponsive T cells from SEB-injected mice was not proliferated by the in vitro stimulation of SEB even in the presence of MEL14. This result indicates that signaling via L-selectin does not rescue the unresponsiveness of T cells. Then we analyzed how MEL14 enhanced T cell proliferation. We demonstrated thatenhancement of T cell proliferation by MEL14 is not due to increase in IL-2 production, which is a common feature of non-CD28 type costimulatory molecules.