Which statement best describes IFN-γ's effect on antigen presentation?

Which statement best describes IFN-γ's effect on antigen presentation?

• A. Stimulates antigen presentation by MHC class II molecules
• B. Inhibits MHC expression
• C. Blocks IL-2 production
• D. Promotes T cell activation

Answer: (A)

Interferon-γ enhances how the immune system presents antigens to helper T cells by upregulating MHC class II molecules on antigen-presenting cells like macrophages and dendritic cells. It does this primarily through inducing CIITA, the master regulator of MHC II transcription, so more peptide fragments can be displayed on the cell surface for recognition by CD4+ T cells. This boost in MHC class II presentation is a direct way IFN-γ strengthens antigen presentation, supporting a stronger helper T cell response and more effective activation of downstream immunity. Inhibiting MHC expression is the opposite of what IFN-γ does, and while IFN-γ can indirectly support T cell activation by improving presentation, the statement about stimulating MHC II–mediated antigen presentation captures the key, direct effect.

Interferon-γ enhances how the immune system presents antigens to helper T cells by upregulating MHC class II molecules on antigen-presenting cells like macrophages and dendritic cells. It does this primarily through inducing CIITA, the master regulator of MHC II transcription, so more peptide fragments can be displayed on the cell surface for recognition by CD4+ T cells. This boost in MHC class II presentation is a direct way IFN-γ strengthens antigen presentation, supporting a stronger helper T cell response and more effective activation of downstream immunity. Inhibiting MHC expression is the opposite of what IFN-γ does, and while IFN-γ can indirectly support T cell activation by improving presentation, the statement about stimulating MHC II–mediated antigen presentation captures the key, direct effect.