PURPOSE: To efficiently purify the titled compound useful as a reagent for immunological measurements for detecting inflammations, etc., by adsorbing and eluting human C reactive Protein (human CRP) by adsorption chromatography using a monoclonal antibody of anti-human CRP.

CONSTITUTION: BALB/C mouse is immunized against human CRP, its splenocyte is collected and subjected to cell fusion with a myeloma cell to give a hybridoma, which is cloned to give a monoclone. It is cultivated to give an anti-human CRP monoclonal antibody CRB18. Then, it is bonded to agarose gel activated with BrCN, etc., to give adsorption chromatography gel. It is packed into a column, CRP-containing serum, etc., is passed through the column, CRP is adsorbed on it, an eluting solution is passed through the column and the adsorbed CPR is eluted to recover and to purity human CRP.