IRAK-4 and MyD88 deficiencies impair antibacterial IgM responses. Levels of (A) IgM and (B) IgG specific for SP capsules, PC, SP TA, and SA TA. MyD88-deficient subjects (▲). (C) Amount of C3a released from serum after incubation with designated pneumococcal antigens. Control (n = 8), IRAK-4 deficient (n = 8), MyD88 deficient (n = 3). Data are results from 1 of 2 replicate experiments. (D) Levels of C3a detected in serum after incubation with PC correlate with levels of PC-specific IgM. P value represents the Spearman rank correlation test. *P < .05, **P < .01, ***P < .001.