Cutting edge: Virus-activated CD8 T cells and lymphokine-activated NK cells express the mast cell function-associated antigen, an inhibitory C-type lectin

The mast cell function-associated Ag (MAFA) is an inhibitory C-type lectin that was originally identified on the cell surface of a rat mucosal mast ce ll line, RBL-H-2(3), We have cloned the mouse homologue of the rat MAFA gen e, and Northern blot analysis revealed that mouse MAFA (mMAFA) gene express ion was strongly induced in effector CD8 T cells and lymphokine-activated N K cells but not in effector CD4 T cells and in mouse mast cells. Moreover, mMAFA gene expression was only found in effector CD8 T cells that had been primed in vivo with live virus because in vitro activated CD8 T cells did n ot express mMAFA, Primary sequence comparison revealed a high degree of con servation (89% similarity) between rat MAFA and mMAFA, Thus, the MAFA molec ule in the mouse is a putative inhibitory receptor on anti-viral CD8 T cell s induced in vivo and on NK cells.