Distribution of T and B cells in thymus, blood and lymph nodes of the cat.

The proportions of T and B cells in the thymus, blood and lymph nodes were estimated in cats from three months to three years of age. T cells were identified by formation of E rosettes with guinea-pig red blood cells and B cells by the presence of surface immunoglobulin (Ig) as shown by the mixed antiglobulin reaction. Using a double test, it was shown that these methods identify separate, non-overlapping cell populations. The proportions of T cells shown in the thymus ranged from 10-73 per cent, in the blood 5-62 per cent and in the nodes, 5-44 per cent. Cells with surface Ig ranged from 0-10 per cent in the thymus, 26-68 per cent in the blood and 32-18 per cent in the nodes. Two cats with lymphadenopathy had unusually high B cell counts and one cat with depletion of the thymus was deficient in peripheral T cells. Papain treatment reduced or abolished E rosette formation by T cells.