In TB immunity is provided by –
**Core Concept**
Immunity to tuberculosis (TB) is primarily cell-mediated, involving the activation of **T lymphocytes** and the production of **cytokines**. This type of immunity is crucial for controlling the infection caused by **Mycobacterium tuberculosis**.
**Why the Correct Answer is Right**
The correct answer is related to the cell-mediated immunity provided by **T cells**, specifically **CD4+ T cells**, which play a key role in organizing the immune response against TB. These cells activate **macrophages** to kill the ingested bacteria, thereby containing the infection.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while **B cells** and antibodies are part of the immune response, they are not the primary mechanism of immunity against TB.
**Option B:** Incorrect as it does not specifically relate to the primary mechanism of immunity against TB.
**Option D:** Incorrect because, although **complement** system helps in opsonization, it is not the primary method of immunity against TB.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that **cell-mediated immunity** is crucial for defense against intracellular pathogens like **Mycobacterium tuberculosis**.
**Correct Answer:** D. Cell Mediated Immunity.