Rat antibodies bearing idiotypes of mouse antibodies against bromelain-treated mouse RBC.

Part of mouse antibodies reactive with bromelain-treated mouse RBC (BrMRBC) use VH12 and VK4 genes, and VH12/VK4-type antibodies are detectable specifically with rabbit anti-idiotype (Id) antibodies (here referred to as RAIb). This study showed that normal rat sera contained RAIb+ IgM at concentrations of 1-6 micrograms/ml. Rat spleens had many anti-BrMRBC B cells, most of which secreted RAIb+ IgM. Hybridomas of spleen cells from LPS-injected rats were screened with RAIb-binding and BrMRBC-hemolytic activity. We found 48 BrMRBC-hemolytic wells, which included all of 39 RAIb(+)-wells. From anti-BrMRBC wells, 7 RAIb+ monoclonal antibodies (mAb) were isolated. All the RAIb+ mAb could react with phospholipid antigens. Rat RAIb+ antibodies, as well as mouse RAIb+ antibodies, can be regarded as antiphospholipid antibodies reactive with BrMRBC. The interspecies expression of RAIb-Id on mouse and rat anti-BrMRBC antibodies indicates that some (antigenic) selective forces may act strongly to conserve the Id (V genes).