CD40LG and Immunodeficiency: Decreased IgM levels are observed in primary immune deficiencies (severe combined immune deficiency, agammaglobulinemia (Bruton's disease), congenital IgM deficiency), or secondary immunodepression (inflammatory diseases of the colon, nephrotic syndrome, burns, and other conditions associated with protein loss, exposure to immunosuppressants, cytostatic medicines, and radiation).