Immune responsiveness of SM/J mice: hyper NK cell activity mediated by NK 1+ Qa 5- cells.

Compared with other inbred strains, SM/J mice have both abnormally high responses to B cell mitogens and hyper NK cell and K cell activity. This hyper NK cell activity is evident even in older SM/J animals, and a high proportion of SM/J nylon-nonadherent lymphocytes that bind target cells also have lytic activity. The SM/J NK cells are NK 1+, Qa 5-, but H-2v identical B10.SM congenic mice have normal NK activity and NK 1+, Qa 5+ NK cells. Together these results suggest the elevation of NK cell activity in SM/J mice is due to chronic activation or maintenance of a Qa 5- NK cell subset. The genetic control of B cell responsiveness and NK cell activity was examined in (B6 x SM)F1 x B6 backcross progeny and (A x SM)F2 intercross mice. No correlation between NK levels and mitogen responsiveness was detected. NK levels in SM/J mice appear to be under polygenic, non-H-2 gene control.