Publications

The systemic autoimmune syndrome of MRL/Mp-lpr/lpr (MRL/lpr) mice consists of severe pan-isotype hypergammaglobulinemia, autoantibody production, lymphadenopathy, and immune complex-associated end-organ disease. Its pathogenesis has been largely attributed to helper alphabeta T cells that may require critical cytokines to propagate pathogenic autoantibody production. To investigate the roles of prototypical Th1 and Th2 cytokines in the pathogenesis of murine lupus, IFN-gamma -/- and IL-4 -/- lupus-prone mice were generated by backcrossing cytokine knockout animals against MRL/lpr breeders. IFN-gamma -/- animals produced significantly reduced titers of IgG2a and IgG2b serum immunoglobulins as well as autoantibodies, but maintained comparable levels of IgG1 and IgE in comparison to cytokine-intact controls; in contrast, IL-4 -/- animals produced significantly less IgG1 and IgE serum immunoglobulins, but maintained comparable levels of IgG2a and IgG2b as well as autoantibodies in comparison to controls. Both IFN-gamma -/- and IL-4 -/- mice, however, developed significantly reduced lymphadenopathy and end-organ disease. These results suggest that IFN-gamma and IL-4 play opposing but dispensable roles in the development of lupus-associated hypergammaglobulinemia and autoantibody production; however, they both play prominent roles in the pathogenesis of murine lupus-associated tissue injury, as well as in lpr-induced lymphadenopathy.

NKG2 is a small family of type II transmembrane proteins possessing extracellular C-type lectin domains expressed primarily on NK cells. The function of these proteins is unknown. We have developed mAbs that recognize NKG2 family members on Western blots. Examination of cell extracts from NK cell clones demonstrates that individual NKG2 family members are expressed on subsets of NK cells. Because the anti-NKG2 mAb do not react with the cell surface Ag, signaling function was studied by generating cell lines that express a chimeric receptor consisting of a cytoplasmic and transmembrane domain from NKG2-A or NKG2-C fused to the extracellular segment of mouse NKR-P1C (NK1.1 Ag). Transfectants of the rat NK cell line, RNK-16, were tested for the effect of anti-NK1.1 mAb on cytolytic activity against the FcR+ target cell lines, P388D1 and P815. The anti-NK1.1 mAb stimulated lytic activity and calcium mobilization in the NK cell line expressing the NKG2-C/NKR-P1C chimeric receptor. By contrast, anti-NK1.1 inhibited the lytic activity and failed to stimulate a calcium response in cells expressing the NKG2-A/NKR-P1C chimeric receptor. Immunoprecipitation experiments demonstrated that the inhibitory cytoplasmic tyrosine phosphatase SHP-1 selectively associates with the NKG2-A/NKR-P1C chimeric receptor, but not with the stimulatory NKG2-C/NKR-P1C receptor. These data indicate that NKG2-A and NKG2-C deliver, respectively, inhibitory and activating transmembrane signals in NK cells.