In MAC-LD, patients with co-morbidity had lower MAC-GPL antibody levels than those without (1.50 vs. 5.54 IU/ml, p=0.009) and patients with malignancy had lower serum GPL IgA levels than those without (0.40 vs. 4.70 IU/ml, p=0.018). The gene discussed is CD79A; the disease is cancer.