Antibody response to common human viruses is shaped by genetic factors

donors (Fig 2, A and B). Patients with PGM3, known to cause a severe phenotype, had less expression of gp130 than did those with PGM3 (Fig 2, A and B), a finding attributed to the more profound impairment of glycosylation caused by the p.Glu340del mutation. PGM3 gene silencing will definitely further confirm the role of PGM3-dependent glycosylation in gp130 signaling. We also assessed the effect of tunicamycin, an inhibitor of N-glycosylation, on gp130-mediated signaling in EBV cell lines from a healthy donor. Tunicamycin treatment gradually replaced the glycosylated form of gp130 (;130 kDa) with its unglycosylated form (100 kDa) and inhibited STAT3 activation in response to IL-6 (Fig 2, C and D). The absence of the lower 100-kD band, corresponding to the unglycosylated gp130 isoform in the patients’ lysates (Fig 2, B), is likely due to proteasomal degradation, as has been seen in another study. Our results are consistent with the observation that N-glycosylation inhibition of gp130 abolishes IL-6–driven STAT3 activation in cultured cardiac myocytes. Collectively, our findings demonstrate that defective glycosylation in PGM3-deficient patients results in reduced expression of unglycosylated gp130 protein and consequently, impaired gp130-dependent STAT3 phosphorylation. This may account for the overlapping clinical features shared by PGM3 deficiency, AD-HIES, and gp130 deficiency. Indeed, we have shown that PGM3-deficient patients have defective IL-6 and IL-27 signaling. Impaired IL-6/gp130/STAT3 signaling in PGM3-deficient patients could explain in part low IL-17–producing T cells generated in vitro as well as lowmemory B cells. In addition, the impairment of T-cell proliferation and the increased proportion of TH2 cells observed in PGM3-deficient patients could be attributed to aberrant IL-27 signaling. Indeed, several reports showed that IL-27 plays a critical role in the suppression of TH2 responses. 9 Altogether, these functional cellular phenotypes observed in PGM3-deficient patients overlap with STAT3 loss of function and gp130-deficient patients and mechanistically tie the PGM3 deficiency to poor gp130-dependent STAT3 signaling.