Detection of Lea substance in saliva stains by enzyme-linked immunosorbent assay (ELISA) using anti-gum arabic serum

It is known that rabbit anti-gum arabic (GA) serum has cross-reactivity with Lea antigen, and that, by using this cross-reactive anti-Lea antibody, the presence of Lea antigen in red blood cells and saliva can be demonstrated with accuracy. We have devised a rapid and highly sensitive method for detecting Lea substance in human saliva by the enzyme-linked immunosorbent assay (ELISA) method using an anti-Lea antibody isolated from anti-GA serum by affinity chromatography on Synsorb Lea. The ELISA plate, coated with the specific anti-Lea antibody, adsorbed the Lea substance in saliva which was subsequently identified by adding enzyme labeled anti-Lea IgG in that order. The method could detect the Lea substance in Le(a+) saliva stains as small as 0.1 by 0.1 cm in size that had been stored at room temperature for three weeks and in Le(a+) saliva stains 0.7 by 0.7 cm in size that had been stored for ten years. This method seems to be useful for quantitative analyses of the Lea substance in various body fluids.