**Core Concept**
The tuberculin test (Mantoux test) detects the presence of sensitization to tuberculin proteins, specifically purified protein derivative (PPD), which are derived from *Mycobacterium tuberculosis*. It reflects a delayed-type hypersensitivity (DTH) reaction mediated by T-cells, indicating prior exposure to TB antigens.

**Why the Correct Answer is Right**
The tuberculin test measures the immune system's response to tubercle proteins. A positive reaction indicates that the individual has been previously exposed to TB antigens—either through past infection or active disease. This sensitivity is due to the activation of memory T-cells that recognize specific antigens like PPD. The test does not assess current infection or resistance, nor does it predict susceptibility or immunity.

**Why Each Wrong Option is Incorrect**
Option B: A positive test does not indicate resistance to TB; rather, it shows immune recognition of TB antigens. Resistance to TB is not assessed by this test.
Option C: Susceptibility to TB is not directly measured; the test reflects prior exposure, not risk of future infection.
Option D: The test does not confirm protective immune status; a positive result may occur in latent or active TB, and it does not guarantee protection against infection.

**Clinical Pearl / High-Yield Fact**
A positive tuberculin test only indicates exposure, not active disease. It is used in screening for latent TB infection, especially in high-risk populations. Always interpret results in context with clinical history and chest X-ray.

✓ Correct Answer: A. Previous or present sensitivity to tubercle proteins