Consistent with a hypomorphic effect, we find that the MM risk allele also associates with reduced levels of immunoglobulin A (IgA) and G (IgG) in healthy subjects (P=8.6 × 10−9 and P=6.4 × 10−3, respectively) and, potentially, with an increased risk of bacterial meningitis (OR=1.30; P=0.0024). This evidence concerns the gene CD79A and bacterial meningitis.