Interferons and cell sources: Which type of interferon is primarily produced by T lymphocytes in response to immune activation?

Introduction / Context:
Interferons are cytokines with antiviral, immunomodulatory, and antiproliferative actions. Recognizing which cells produce which interferon subtype is important in immunology.

Given Data / Assumptions:

• Type I interferons include interferon-α and interferon-β, produced by many cells including plasmacytoid dendritic cells and fibroblasts.
• Type II interferon is interferon-γ, produced mainly by activated T lymphocytes and NK cells.
• Interferon-γ has potent macrophage-activating and Th1-skewing effects.

Concept / Approach:
Match interferon subtype to its predominant cellular source. T cells are classically linked to interferon-γ production during cell-mediated responses.

Step-by-Step Solution:
Identify T lymphocyte-associated interferon: interferon-γ. Exclude interferon-α/β (type I, broad cellular sources). Select option “γ”. Note that NK cells also produce interferon-γ, reinforcing its immune role.

Verification / Alternative check:
Clinical assays measuring interferon-γ release (e.g., TB IGRA tests) demonstrate T cell-derived IFN-γ responses.

Why Other Options Are Wrong:
α and β are type I interferons not specific to T cells; combining γ with β is inaccurate for source specificity; λ is a distinct family with mucosal roles.

Common Pitfalls:
Assuming all interferons are produced by the same cell types; mixing type I and type II categories.

Final Answer:
γ.