Suppression of Immune Responses by CD8 Cells. II. Qa-1 on Activated B Cells Stimulates CD8 Cell Suppression of T Helper 2 Responses

We have investigated the role of MHC class I products and CD8 T cells in regulating Ab responses using beta2-microglobulin deficient (beta2m-/-) mice. Beta2m-/- mice produced stronger IgM and IgG responses than did control beta2m+/+ mice to both cellular and viral Ags. These Ab responses could be suppressed by infusion of activated B cells from beta2m+/+ mice. Further investigation showed that the beta2m-associated molecule on activated B cells that induced CD8 suppression was Qa-1 and that the Th2 component of CD4 cells was most affected by CD8-suppressive activity. Our findings suggest a novel pathway of Th inhibition in which B cell presentation of Qa-1-associated peptides stimulates CD8 suppressive activity.