Study of idiotypes expressed by monoclonal antibodies to the 35 kD and 12 kD antigens of Mycobacterium leprae.

Rabbit antisera were raised against four monoclonal antibodies (MoAb) binding with the 35 kD protein and four MoAb binding with the 12 kD protein antigen of Mycobacterium leprae. Antisera showed idiotype (Id) specificity following cross-absorption with normal mouse globulin. One Id on a single MoAb and another Id shared between three MoAb were identified for each group. Functional studies were carried out with the Rb04 anti [anti-35 kD] specificity. The expression of this Id and paratope in antigen immunized mice was associated with Igh alleles. Inoculation of mice with anti-Id Rb04 induced an 'Ab3' serum response of corresponding Id specificity only when the anti-Id was given in emulsion with incomplete Freund's adjuvant (IFA). Conversely, prior injection of soluble anti-Id inhibited the subsequent Ab3 response to Rb04/IFA. Moreover, the suppressive effect of soluble anti-Id was abrogated by prior injection of 50 mg/kg cyclophosphamide. These results indicate that regulatory mechanisms similar to those involved in antigenic stimulation may explain the stimulatory or suppressive potency of anti-Id antibodies. Finally, the Ab3 responses to the two tested anti-Ids did not contain any antigen binding activity.