IL-12Rβ1–deficient subjects display low-avidity TT-specific IgG. (A) Serum IgM, IgG, and IgA levels in IL-12Rβ1–deficient subjects (n = 25) and control subjects (n = 38). Student t test. (B) Serum Ig levels at different ages. Each dot represents a sample from an individual subject. Linear regression and 95% confidence interval in each group (control or IL-12Rβ1 deficient) are indicated by solid lines and dotted lines, respectively. (C) CD138 staining of peripheral LN samples from IL-12Rβ1–deficient subjects and tonsil samples from control subjects. T-B cell aggregates in subject 2 are indicated by dotted lines. In control tonsils, secondary follicles are indicated by dotted lines, and the solid lines indicate the border between the mantle zone (MZ) and the GC. Bar equals 100 μm. (D) CD138⁺ cells with plasma cell morphology. Bar equals 10 μm. (E) TT-specific IgG of serum samples were assessed by enzyme-linked immunosorbent assay. IgG avidity was assessed by the index calculated as a percentage: (OD after urea treatment/OD of the reference well) × 100. (F) Rubella virus–specific IgG levels and their avidities were assessed by enzyme-linked immunosorbent assay. (G) Serum IgG levels against Epstein-Barr virus, cytomegalovirus, and varicella virus in IL-12Rβ1–deficient subjects and control subjects. Student t test.