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Abstract
This study was undertaken to determine the effects of aging on lymphocyte subsets in the peripheral blood and spleens of Sprague-Dawley rats. Rats aged 3, 13 and 26 months were used in the study. Analyses of dual labeled lymphocytes from the 26 month animals show decreases in the numbers of lymphocytes due to decreased cellularity (spleen) or reduced lymphocyte percentages within the total white blood cell population (peripheral blood). In the spleens and blood of the oldest rats, there were reduced numbers of Total T, T helper/ amplifier (Th/a), virgin Th, and natural killer (NK) cells. Other changes were observed in the spleen but not peripheral blood. The numbers of T cytotoxic/suppressor cells (Tc/s) B cells, “autoimmune” B cells and NK cells were reduced in the spleen but remained within normal limits in peripheral blood. The data show aging exerts different effects on the peripheral blood and splenic compartments of the immune system. These differences may have teleological significance in relation to immune responses to xenobiotics and neoplastic cells.