ALTERATIONS IN CD8-ASSOCIATED LYMPHOID-TISSUES (GALT) OF THE AGING FISCHER-344 RAT - A CORRELATED IMMUNOHISTOCHEMICAL AND FLOW CYTOMETRIC ANALYSIS( CELL DISTRIBUTION IN GUT)

The distribution of CD8+ phenotype (cytotoxic/suppressor) T lymphocyte s in Peyer's patches and intestinal lamina propria in young adult (3-6 months) and old (24-29 months) Fischer 344 rats was examined using im munohistochemical and flow cytometric analyses. Flow cytometric analys is confirmed previous reports indicating no change with age in the pro portion of Peyer's patch CD8+ cells in the rat. Immunohistochemical an alysis showed discrete zones of densely stained CD8+ cells in the inte rfollicular areas and weakly stained cells within the follicles in Pey er's patches in yong adult animals. In old rats, the number of intense ly stained CD8+ cells between the follicles was markedly reduced and p ositively stained cells were distributed throughout the Peyer's patche s. In addition, the population density of CD8+ cells is more diffuse i n old animals, the number of CD8+ lymphocytes in the intestinal lamina propria increased 2.5-fold with aging from 533 +/- 59 cells/mm2 in yo ung adult to 1312 +/- 83 cells/mm2 in old rats. The findings suggest t hat CD8+ cell distribution in the inductive and effector sites of gut associated lymphoid tissue undergoes age-related shifts.