The mean concentrations of IgG (8.66±2.58 g l−1) and IgM (0.35±0.12 g l−1) in the ovarian cancer patients’ AFs were lower than the average concentrations in normal human sera, despite the fact that the total protein concentrations in the malignant AFs were 93–140% of the serum values. The gene discussed is CD40LG; the disease is ovarian carcinoma.