Description: The monoclonal antibody H1.1 recognizes gp49, a receptor with structural similarities to the PIR (paired Ig-activating receptors) and ILT/KIR(killer inhibitory receptors) family of proteins. Two closely linked genes on mouse chromosome 10 encode the related proteins gp49A and gp49B. These two receptors are almost 90% identical in their extracellular regions but differ in their cytoplasmic domains; gp49B contains an ITAM domain while gp49A does not and is extremely short. Expression of gp49 was originally identified on mast and LAK (IL-2 activated NK) cells. Expression on LAK cells has been shown to be predominantly gp49B with only a small amount of gp49A. Additionally gp49 is found on myeloid cells. Detailed function is not known but gp49B can inhibit cellular activation. The monoclonal antibody H1.1 recognizes both gp49A and gp49B.