The effect of cyclophosphamide in vivo on the expression of lymphocyte markers, detected by monoclonal antibodies, in the rat.

Surface markers on lymphocytes from the thymus, lymph node and spleen of the rat were examined in single cell suspensions using a panel of monoclonal antibodies. These were used particularly to investigate Pan T, TH (T-helper), TS/C (T-suppressor-cytotoxic) and Ia antigens. The expression of these markers in rats treated with a single dose of cyclophosphamide (100 mg/kg body weight) was followed for 3 weeks after treatment. Maximum changes were detected at 3 days and recovery took up to 3 weeks to near completion. Comparison was made with histological observations of the effect of CY on these organs. At 3 days, the thymus showed maximum weight loss and gross cortical depletion. This associated with significant drop in the expression of the TS/C marker on small and large lymphocytes. Regeneration of the cortex, beginning at 7 days, was associated with the presence of many large pyroninophilic cells. This was accompanied by an increase in the expression of the TS/C marker on both small and large lymphocytes. The mesenteric lymph node showed marked depletion of the B-cell areas at 3 days. There was also a significant drop in TS/C and Ia expression and a marked rise in Pan T and TH. TS/C expression recovered rapidly with a rebound at 7 days. However, the expression of Pan T and TH did not return to normal until 21 days. In the spleen there was a similar decrease in the lymphocytes populating the B-cell areas at 3 and 7 days with an increase in the expression of Pan T and TH, and a decrease in the expression of Ia.(ABSTRACT TRUNCATED AT 250 WORDS)