Identification of possible calcium dependent antigens in lithium diiodosalicylate extraction of group A, type 12 streptococcal cell membranes.

Group A, type 12 streptococcal cell membranes were extracted by aqueous lithium diiodosalicylate (LIS) and the extract treated with trifluorotrichloroethane (Genetron). An initial component was isolated (GLCM) which was soluble in aqueous buffer, but was heavily contaminated with LIS. Dialysis of GLCM vs. 0.01 M Tris-EDTA (TE) buffer yielded a weakly antigenic component, TE-GLCM, with negligible contamination by LIS. Subsequent dialysis of TE-GLCM vs. isotonic calcium chloride produced two fractions, a soluble one (CMS) and a precipitate (CMP). It was demonstrated that CMS possessed immunological characteristics distinct from TE-GLCM and CMP. CMS was shown to be a calcium dependent antigen, and immunologically related to human glomerular basement membrane (GBM) antigens.