**Core Concept**
Interferon gamma (IFN-γ) is a cytokine that plays a crucial role in the immune system's response to infections, particularly those caused by intracellular pathogens. It enhances the cytotoxic effects of macrophages by promoting their activation and maturation.

**Why the Correct Answer is Right**
IFN-γ is secreted by T cells, specifically by CD4+ and CD8+ T cells, in response to antigen presentation. This cytokine binds to its receptor on the surface of macrophages, activating the JAK-STAT signaling pathway, which leads to the production of nitric oxide and the enhancement of macrophage cytotoxicity. This is essential for the elimination of infected cells and the control of intracellular pathogens.

**Why Each Wrong Option is Incorrect**
**Option A:** Natural Killer (NK) cells are involved in innate immunity and can kill tumor cells and virus-infected cells, but they are not the primary source of IFN-γ.
**Option B:** Dendritic cells are antigen-presenting cells that play a crucial role in initiating immune responses, but they do not secrete IFN-γ.
**Option C:** B cells are responsible for producing antibodies, but they are not the primary source of IFN-γ.

**Clinical Pearl / High-Yield Fact**
IFN-γ is a key cytokine in the immune system's response to tuberculosis (TB) and other intracellular pathogens. Its deficiency or dysregulation can lead to increased susceptibility to TB and other infections.

**Correct Answer:** C. T cells