Cold Reacting Antibody in NZB/Bl Mice

NZB/Bl mice produce throughout life cold reacting antibodies (CRA) with specificity to the I-erythrocyte antigen. These antibodies do not react with autologous erythrocytes since intact mouse erythrocytes do not carry reactive I-antigen. This antigen on the other hand is widely distributed in NZB/Bl mouse tissues. Newborn CF₁ mice injected with cell-free filtrates of NZB/Bl mouse spleen produce CRA. The untreated offspring of these animals also synthesize this type of antibody suggesting that this immune response is induced by a self-replicating, ultrafilterable immunogen. CRA in NZB/Bl mice may, therefore, be another example of the induction of an auto-immune response by an infectious agent.