Quantitative histochemical studies of the effect of levamisole on splenic T-cells in thymectomized Bufo bufo larvae.

The ability of levamisole (LVS) to correct the effect of thymectomy on splenic T-cell population in Bufo bufo larvae was tested. Using the nonspecific acid alpha-naphthyl acetate esterase (ANAE) technique, the T-lymphocytes displayed a characteristic reddish brown spot (T-pattern). The total number of white cells per spleen and the number of T-pattern cells per 100 splenic white cells were determined. In addition, differential counts of the T-patterns were made on the basis of the size of their spots. Thymectomized larvae in comparison to sham-operated larvae possessed a lower total number of splenic white cells with a similar proportion of T-pattern cells, but a lower proportion of cells with a large T-pattern. After seven days of LVS treatment, the thymectomized larvae showed an increased total number of splenic white cells and an increased proportion of cells with a large T-pattern, both data falling within normal limits. The effect of LVS appeared marked in thymectomized larvae, but was slight or absent in sham-operated larvae. Differential counts of the large T-pattern cells, based on the size of ANAE reaction product, showed the capacity of LVS to stimulate T-cell maturation. It was concluded that LVS induced proliferation and differentiation of splenic T-cells and that the different sizes of T-pattern reaction represent different maturational stages of T-cells.