Auto-anti-idiotypic antibodies inhibit T-cell-mediated hypersensitivity in BCG-infected mice.

It is shown that serum from mice heavily infected with BCG contains antibodies which block the cell transfer of delayed-type hypersensitivity (DTH) to purified protein derivative (PPD) when BCG-immune cells were preincubated in it. This suppressive activity is antigen specific in that the serum does not block the cell transfer of contact sensitivity to oxazolone. However, the suppressive activity is not antigen directed in that it is absorbed neither by PPD-coupled Sepharose beads nor by PPD-pulsed normal peritoneal exudate cells. On the other hand, the activity can be absorbed to BCG-immune T cells and eluted from a Sepharose column conjugated with affinity-purified mouse anti-PPD antibodies. The possibility that antireceptor antibodies arise during the BCG infection and regulate DTH reaction is discussed.