Fig 1: Specificity and sensitivity of IgA detection.Purified human IgG, purified SIgA and recombinant IgA1 lambda (see Online Methods) were coated on to ELISA plates and detected with the same goat anti-human IgA-HRP conjugate used in the assays to detect saliva and serum IgA S-protein antibodies. The plot shows net OD450 values as a function of the amounts of the three antibodies added to the ELISA wells during the coating stage.