Selective and specific inhibition of 24-hour skin reactions in the guinea-pig. II. The mechanism of immune deviation.

Guinea-pigs injected with antigen in Freund's complete adjuvant develop delayed hypersensitivity to the antigen. This is reduced by the prior injection of the same antigen precipitated with alum. This may be termed immune deviation and has been shown to differ from immune tolerance. Four possible mechanisms for this phenomenon were considered: (a) that there was a specific defect in the cell population responsible for the passive transfer of delayed hypersensitivity; (b) that there was an antibody blocking the detection of delayed hypersensitivity; (c) that there was an antibody blocking the induction of delayed hypersensitivity; and (d) that the cells responsible for delayed hypersensitivity were desensitized . Experiments on the passive transfer of delayed hypersensitivity from deviated and control guinea-pigs showed that there was a defect in the cell population involved in the passive transfer of delayed hypersensitivity. Serum transfer failed to reveal evidence of antibody blocking the induction or detection of delayed hypersensitivity. Transfer of cells into recipients which had been pretreated with alum-precipitated antigen gave no evidence of desensitization in the PPD system. The findings with bovine γ-globulin were equivocal. It was concluded that there was a defect in the cell population involved in the passive transfer of delayed hypersensitivity and, in the absence of evidence for other mechanisms, this was attributed to a direct effect of the first injection of antigen on the cells responsible for the state of delayed hypersensitivity after the injection of the same antigen in Freund's complete adjuvant.