STUDIES OF ACUTE PHASE PROTEIN. III. ELICITATION OF CX-REACTIVE PROTEIN IN RELATION TO IMMUNE ELIMINATION OF ANTIGEN AND APPEARANCE OF CIRCULATING ANTIGEN-ANTIBODY COMPLEXES.

Following the injection of I131-labeled BSA into rabbits, CxRP was found to appear in the serum of one half of the animals demonstrating an immune response. The time of appearance of CxRP indicated that the inflammation began coincident with or immediately following the appearance of immune complexes in the circulation. It was not possible to differentiate on the basis of the level of circulating antigen-antibody complexes or the day of onset of immune elimination between animals with and those without CxRP responses. It was considered probable that the CxRP response was related to an inflammatory effect of circulating antigen-antibody complexes. The serum level of CxRP, measured by a quantitative immunochemical procedure, was not related to the level of circulating antigen-antibody complexes, as measured by the Farr technique. Quantitative levels of CxRP stimulated by antigen-antibody complexes were in the low or moderate range as compared with responses to other inflammatory stimuli, such as typhoid vaccine or croton oil.