Immunobilan testing measures immunoglobulin A which is IGA and immunoglobulin M which is IgM. In healthy individuals pathogenic bacteria are found in low quantities in the gut and antibody titers in the blood are very low. With bacterial overgrowth, large quantities of IgA are produced and some IgA will be found in the bloodstream. High titers of IgM for intestinal bacteria is an indicator of increased intestinal permeability.