Lamina Propria T Cell Subsets in the Small and Large Intestine of Euthymic and Athymic Mice

We investigated lamina propria T cells from the small intestine (jejunum/ileum) and the large intestine (colon) of euthymic (BALB/c, C. B-17, C57BL/6) and athymic (C57BL/6 nu/nu; BNX bg/bg nu/nu xid/ xid) mice. CD3+ T cells represented about 40% of the lamina propria lymphocytes (LPL) from the small or the large intestine of euthymic mice, and 20–30% of the LPL populations from the small or large intestine of athymic mice. In the lamina propria T cell population of the small intestine, 85% were of the αβ lineage in euthymic mice, but only 40% were of the αβ lineage in athymic mice. T cells of the αβ lineage were thus more frequent than T cells of the αβ lineage in the intestinal lamina propria T cells of extrathymic origin. CD4+ T cells represented 40% of the lamina propria T cells in the small as well as in the large intestine of euthymic mice, and 20–30% of the T cells in the lamina propria of the nude mouse gut. In euthymic mice, 40% of the T cells in the small intestine lamina propria, and 30% of the T cells in the colonic lamina propria were CD8+, In intestinal lamina propria T cell populations of athymic mice, the CD8+ T cell population was expanded. Most (60–70%) CD8+ T cells in the lamina propria of the small and the large intestine of euthymic and athymic mice expressed the homodimeric CD8α+β− form of the CD8 coreceptor. A fraction of 15–20% of all CD3+ T cells in the lamina propria of the small and the large intestine of euthymic and athymic mice were ‘double negative’ CD4− CD8−. A large fraction of the TCRαβ+ T cells in the colonic lamina propria (but not in the small intestine lamina propria) of euthymic mice expressed the CD2 and the CD28 costimulator molecules, the adhesion molecule LECAM-1 (CD62 L), and could be activated in vitro by CD3 ligation. These data reveal a considerable heterogeneity in the surface phenotype and the functional phenotype of murine lamina propria T cells.