Immunoconglutinin associated with nonspecific acquired resistance in malaria, babesiosis, and other anemia-inducing infections.

Rats recovered from infectious anemias had an acquired nonspecific resistance. Recovery from trypanosomal and babesial infections enhanced the resistance to infections with filterable rat infectious anemia (RIA) agent, and recovery from RIA made rats more resistant to plasmodial, babesial and trypanosomal infections. The resistance was manifested after challenge by reduced parasitemia accompanied by significant anemia, which became evident 2 or 3 days earlier in recovered rats than in controls. Mortality of the recovered rats was less than that of the controls. Immunoconglutinin (IK) was detected with high titers in animals during the acute stage of each infection and remained present with lower titers after recovery. After the recovered rats were challenged with a heterologous agent, the existing IK titers became elevated earlier and usually were higher than those of the controls. However, the infections also stimulated production of cold-active hemagglutinin (CAH). It was therefore not clear that the resistance could be attributed to IK. The nature of antigen-antibody complexes that may have fixed complement and stimulate IK is discussed. However, a specific complex was not implicated.