Lack of IFN-γ production in response to IL-12 and IL-23. PHA-T-cell blasts from a positive control (C+), a negative control (C-), and the patient (P) were plated in 24-well plates and were left unstimulated (NS) or were stimulated with increasing concentrations of IL-12 for 48 hours (A) or IL-23 for 72 hours (B). Supernatants were harvested, and IFN-γ was quantified by ELISA.