Resistance of helper T lymphocytes to cyclophosphamide.

The effect of cyclophosphamide (Cy) on helper T lymphocytes using an adoptive transfer approach in athymic nude mice was investigated. The results indicated that Cy, at a dose (100 mg/kg) which virtually abolished anti-sheep erythrocyte (SRBC) antibody plaque forming cell (PFC) response of Balb/c mice, did not alter significantly the capacity of their splenic T cells to restore the anti-SRBC PFC response of nude mice. This resistance of T helper cells was observed in unimmunized mice and in mice injected with SRBC two days prior to Cy administration. It has been concluded that both resting and antigen stimulated T helper cells responsible for reconstituting anti-SRBC response of nude mice are resistant to Cy.