Antigen Presentation And Cytokines Practice Test

A 1-year-old boy presents with recurrent bacterial and fungal infections, including Pneumocystis jirovecii pneumonia and chronic diarrhea. Laboratory studies show severe lymphopenia, particularly of CD4+ T cells, and hypogammaglobulinemia. Flow cytometry reveals that his peripheral blood mononuclear cells fail to express HLA-DR, -DP, and -DQ molecules on their surface. This patient's defect most directly impairs which of the following immunologic processes?

A 35-year-old woman is diagnosed with tuberculoid leprosy. A skin biopsy from a lesion shows numerous granulomas containing activated macrophages and CD4+ T lymphocytes. The containment of Mycobacterium leprae within these granulomas is heavily dependent on the cell-mediated immune response. Which of the following cytokines, produced by activated T helper cells, is most critical for activating the macrophages in this patient's lesions?