The median functional MBL serum level in the patients with SLE (1.4 μg/ml, range 0.04 to 7.60 μg/ml) was comparable with that in 100 healthy laboratory workers (1.1 μg/ml, range 0.02 to 11.2 μg/ml). The gene discussed is MBL2; the disease is systemic lupus erythematosus.