B6.Kb-Db- mice are devoid of class Ia but express normal levels of class Ib molecules. They have low levels of CD8 T cells in both the thymus as well as peripheral T cell compartments. Although the percentage of splenic CD8αα T cells is increased in these animals, ∼90% of CD8 T cells are CD8αβ. In contrast to B6 animals, most of the CD8 T cells from these mice have a memory phenotype (CD44highCD122high CD62Llow) including both CD8αβ and CD8αα subsets. In the thymus of B6.Kb-Db- animals, there is a decrease in the percentage of SP CD8 T cells, although most are CD44low, similar to that seen in B6 mice. The spleens from day 1-old B6 and B6.Kb-Db- mice have a relatively high proportion of CD44highCD62Llow CD8 T cells. However, by day 28 most CD8 T cells in B6 mice have a naive phenotype while in B6.Kb-Db- mice the memory phenotype remains. Unlike CD44high cells that are found in B6 animals, most CD44high cells from B6.Kb-Db- mice do not secrete IFN-γ rapidly upon activation. The paucity of CD8 T cells in B6.Kb-Db- mice might be due in part to their inability to undergo homeostatic expansion. Consistent with this, we found that CD8 T cells from these animals expand poorly in X-irradiated syngeneic hosts compared with B6 CD8 T cells that respond to class Ia Ags. We examined homeostatic expansion of B6 CD8 T cells in single as well as double class Ia knockout mice and were able to estimate the fraction of cells reactive against class Ia vs class Ib molecules.
ASJC Scopus subject areas
- Immunology and Allergy