HIV Mechanism of Immune Deficiency — NEET Biology

Correct answer: B — S1, S2, S3, and S5 only

The core concept here focuses on the pathogenesis of AIDS and its specific effects on the immune system, including the roles of different cells and types of immunity. S1: This statement is correct. HIV specifically targets and replicates in helper T-lymphocytes, leading to their progressive decrease in number over time, which is a hallmark of AIDS progression. S2: This statement is correct. Macrophages are among the first cells HIV enters after infection, and they continuously produce virus particles, acting as an 'HIV factory'. S3: This statement is correct. The significant reduction in helper T-lymphocytes severely compromises the immune system, rendering the patient vulnerable to various opportunistic infections that a healthy immune system could easily combat, such as those caused by Mycobacterium, viruses, fungi, and parasites like Toxoplasma. S4: This statement is incorrect. HIV primarily targets helper T-lymphocytes and macrophages, not B-lymphocytes directly. While the overall immune response (including humoral immunity mediated by B-cells) is impaired, it's due to the destruction of helper T-cells which are crucial for B-cell activation, not direct targeting of B-cells. S5: This statement is correct. Active immunity is developed when a host's body produces antibodies in response to antigens. The initial immune response to HIV (or any pathogen) is a primary response, which is typically of low intensity but represents active immunity. Therefore, statements S1, S2, S3, and S5 are correct. This question evaluates the understanding of HIV's cellular targets, the consequences of infection, and basic immunity types.