Q. A 2-week-old female neonate is admitted to the neonatal intensive care unit due to sudden deterioration in function (she has become listless and poorly responsive). The mother has had regular prenatal care and she, herself, has no significant medical history. The neonate is up to date for BCG and hepatitis B vaccinations. The neonate has a tumultuous course in the ICU with a general unstoppable deterioration in major organ functions and ultimately succumbs to multi-organ failure and dies. Autopsy reveals malformed granulomas with acid-fast bacilli. An IL-12 receptor deficiency is suspected. A genetic disorder is suspected as being responsible for the IL-12 receptor deficiency. Abnormality/Deficiency of which of the following cytokines is to blame for triggering this patient's cascading deterioration?