STABILIZED ANTIGEN-CONTAINING AQUEOUS SOLUTION

PROBLEM TO BE SOLVED: To stabilize antigen activity of a pulmonary surfactant protein by coexisting the protein and a bivalent metallic ion. SOLUTION: A pulmonary surfactant protein and a bivalent metallic ion of a calcium, barium, magnesium or the like are coexisted to stabilize antigen activity of the pulmonary surfactant protein. The metallic ion is not always necessary to be an aqueous solution state, but may be coexisted with the pulmonary surfactant protein. Not only a solution-like state but also the pulmonary surfactant protein are bonded to a plate, and even if most moisture is removed, if the bivalent metallic ion is coexisted, the surfactant protein can be stabilized. A concentration of the coexisting bivalent metallic ion is in a range of about 0.01 to 100 mM. Thus, a standard stock solution of the surfactant protein needing a low-temperature preservation can be preserved and fed at an ambient temperature. A reaction temperature when measured can be executed at the ambient temperature, and operability of the measurement is remarkably improved.