Ly49A inhibitory receptors redistribute on natural killer cells during target cell interaction

When T effector cells meet antigen-bearing target cells, there is a specifi c accumulation of T-cell receptors, co-receptors and structural proteins at the point of cell-cell contact. Ly49 inhibitory receptors bind to murine m ajor histocompatibility complex (MHC) class I molecules and prevent natural killer-(NK) cell cytotoxicity. In this study we have tested whether inhibi tory receptors accumulate at the point of cell-cell contact when NK cells e ncounter target cells bearing MHC class I ligands for those inhibitory rece ptors. We have used RNK-16 effector cells that express Ly49A receptors and have found that there was a specific accumulation of Ly49A receptors at the point of NK cell-target cell contact when the target cells expressed H-2D( d). We also observed that engagement of Ly49A on NK cells resulted in an al tered redistribution of potential triggering receptors CD2 and NKR-P1. Thes e data indicate that inhibitory receptors, like activating receptors, may s pecifically aggregate at the point of cell-cell contact which may be necess ary for them to mediate their full inhibitory effect.