PURPOSE: To obtain a diagnosing reagent for Kawasaki's disease and infectious disease of Streptococcus pyogenes of group A by using a monoclonal antibody produced by a fused cell between an antibody-forming cell prepared by immunizing a mouse with Streptococcal pyrogenic exotoxin derived from Streptococcus pyogenes of group A and a mouse derived myeloma cell.

CONSTITUTION: A monoclonal antibody produced by a fused cell between an antibody-forming cell prepared by immunizing a mouse with Streptococcal pyrogenic exotoxin(SPE) derived from Streptococcus pyogenes of group A and a mouse derived myeloma cell is used. Streptococcal pyrogenic exotoxin existing in a specimen (e.g. serum of Kawasaki's disease) is assayed by the following method. First, a test solution is mixed with a monoclonal antibody containing Sterptococcal pyrogenic exotoxin, then reacted with enzyme labeled serum immunoglobulin and then treated with a coloring solution and the absorbance of formed color tone at 500nm is measured.