RADIOIMMUNOASSAY FOR THE COMPLEMENT-ACTIVATING COMPONENT OF RA-REACTIVE FACTOR

Ra-reactive factor is a complement activating antimicrobial protein th at reacts to a wide variety of microorganisms, This factor is composed of a mannan-binding lectin and a serine protease, P100, and it activa tes the lectin pathway of complement, In contrast to the mannan-bindin g lectin, a method for the determination of P100 in serum is not estab lished yet because serum level of this factor is very low, In the pres ent paper, we prepared antibodies by immunizing rabbits with oligopept ides derived from the amino acid sequence of P100 and developed the ra dioimmunoassay for the detection of serum P100, In this assay, the ant ibodies reacted specifically with the immunogenic peptides in a range of 4-63 fmol, They did not cross-react with major serum proteins, Alth ough the reactivity of these antibodies to P100 in serum was low, this reactivity was found to be increased by the partial digestion of seru m samples with thermolysin, One of the antibodies reacted to P100 anti gen in serum corresponding to 45 fmoles of oligopeptide after the trea tment at an optimal condition, with a good reproducibility. Therefore, relative amounts of P100 in sera can be assessed by the present metho d, Further improvement for the assay is discussed.