Modulation of the immune system in the mouse. 2. Drug administration following antigen sensitization

The effects of administering drugs 2 days after antigen sensitization in a combined model of delayed type hypersensitivity (DTH) and humoral immunity (HI) in the mouse are described and compared with a previous study in which drugs were administered prior to sensitization using the same model. Low doses of cyclophosphamide (CY) administered after antigen sensitization were found to enhance DTH to methylated bovine serum albumin (MBSA). In addition, high doses of this drug suppressed DTH for 3 days after challenge, and then enhanced the response for a further 5 days. The HI response to sheep red blood cells (SRBC) was simultaneously suppressed by a range of CY doses. A number of different drug types demonstrated a similar pattern of dose-dependent DTH effects. However, unlike the previous study DTH enhancement was not confined to the alkylating agents. Either DTH enhancement or suppression was also observed after treatment with a number of other drugs. HI was suppressed by several drugs, in particular by a number of alkylating agents and anti-metabolites. Selective effects on one or other limbs of the immune response were observed. The mode(s) of action of drugs active in the present study are uncertain but possible explanations are discussed in terms of the elimination and subsequent recovery of specific cell populations.