Bacterial lipopolysaccharides (LPS) derived from a variety of organisms effectively induced C consumption in humans, bovines, and porcines with developmental agammaglobulinemia; birds with experimental agammaglobulinemia; and humans with agammaglobulinemia syndromes. This interaction proceeded even in precolostral piglet sera which contained less than 2.5 x 10(-6) mg/ml gamma globulin, and led to generation of neutrophil chemotactic factor and anaphylatoxin in these sera. Hence, the LPS-C interaction can proceed in sera markedly deficient in immunoglobulin. The question of whether immunoglobulins can be bypassed in the LPS-C interaction, or whether they are regularly utilized in a way so efficient that their participation is masked, was considered.