Composite immunoblot demonstrating the results of an adsorption and elution assay specific for serum IgG, IgA, and IgM recognizing OMPs of H. parainfluenzae (strain CF3115) or E. coli. Lanes: A, low-molecular-mass markers stained with Fast Stain; B, serum adsorbed with E. coli; C, serum adsorbed with H. parainfluenzae; D, native serum (1/200); E, antibodies eluted from E. coli; F, antibodies eluted from H. parainfluenzae; G, buffer-only control. Unlabelled lane, stain for total protein with colloidal gold.