T lymphocytes of young and aged rats. I. Distribution, density, and capping of T antigens.

The distribution, density, and capping of the T cell antigens W3/13, W3/25, and Thy-1 were studied in lymphocytes of young (3 to 4 mo) and aged (greater than or equal to 27 mo) Brown Norway (BN) rats. The total number of W3/13, W3/25, and Thy-1 positive cells and the percentage of Thy-1 positive cells are reduced in the spleens and lymph nodes of aged rats. Analysis of spleen and lymph node cells in a fluorescence-activated cell sorter indicated that with ageing there is a loss of moderately and brightly stained W3/13 and W3/25 positive cells. The density of W3/13, W3/25, and Thy-1 is reduced on spleen and lymph node cells of old rats. The rate of capping of all 3 molecules is diminished on "old" cells. Colchicine treatment of young cells enhanced capping of all 3 molecules and allowed capping of W3/13 by a single ligand. However, capping on "old" lymphocytes was not affected by colchicine treatment. Cytochalasin D inhibited capping to the same extent on young and "old" cells. These results suggest that the membrane composition and cytoskeleton are altered in T lymphocytes of aged rats.