EFFECT OF ALTERNATE-DAY HYDROCORTISONE THERAPY ON THE IMMUNOLOGICALLYIMMATURE RAT .3. CHANGES IN T-CELL AND B-CELL AREAS IN LYMPH-NODES

The histologic effects of the alternate-day hydrocortisone therapy (40 0 mg/M(2) from day 7 to day 19 after birth) were studied on the mesent eric lymph nodes of immunologically immature rats. In rats sacrificed 2 days following the cessation of therapy, depletion of lymphocytes of the thymus-independent area was apparent. Smaller lymphocytes were mo re susceptible to the effect of hydrocortisone than larger ones. The a bsence of primary follicles, normally present at this age, suggested a possible retardation in development of the immune system. B lymphocyt es appeared to be the target of the direct lymphocytolytic effect of h ydrocortisone. In rats sacrificed 23 days following the treatment, imm unological maturity was achieved, indicating the reversibility of the hydrocortisone effect.