Immunoregulatory effect of antibody on delayed-type hypersensitivity in mice.

We analyzed the conditions for in vivo toleration of delayed-type hypersensitivity (DTH). The intravenous injection of a high dose of keyhole-limpet hemocyanin (KLH) into BALB/c mice did not induce DTH in vivo, but the serum titers of the anti-KLH antibody were significantly elevated. This lack of DTH response was antigen-specific, and the intravenous injection of the antigen induced effector-phase suppressor T cells. The findings suggested that the lack of a DTH response brought about by the intravenous injection of a high dose of antigen was not immunological tolerance. Treatment with a high dose (250 mg/kg) of cyclophosphamide - but not a low dose (50 mg/kg) - enhanced the DTH, but suppressed antibody production. These results indicate that humoral immune response participate in the regulation of DTH. In addition, the transfer of serum or immunoglobulin from mice that were injected intravenously with a high dose of the antigen suppressed the DTH. We concluded that the antibodies regulate DTH in the antigen-specific manner.