Immunological studies on Kawasaki disease: II. Isolation and characterization of an immunosuppressive factor in acute phase sera.

Acute phase serum from a patient with Kawasaki disease possessed strong inhibitory activity for the proliferative response of Con A-stimulated peripheral blood mononuclear cells. The inhibitor was fractionated step-wise by means of DEAE-Sephadex A-50 ion exchange chromatography followed by Sephadex G-100 gel filtration and high performance liquid chromatography. A major protein of 140 kD with 2000 times greater inhibitory activity than the original serum was identified in the final fraction. Immunization of mice with this fraction resulted in the production of three hybridoma clones secreting monoclonal antibodies (MoAb) of IgG1 class which blocked the inhibitory activity of the fraction. Two of these MoAb recognized the same epitope of the inhibitory factor, while the remaining MoAb was directed to a different epitope. Western blot analysis of acute phase sera by the MoAb demonstrated the presence of 140 kD molecules in 43 of 55 patients.