Q.19

Which of the following cell types is infected by the human immunodeficiency virus-1?

(A) T-helper lymphocytes

(B) T-cytotoxic lymphocytes

(C) Plasma cells

(D) B-lymphocytes

HIV-1 Targets T-Helper Lymphocytes: MCQ Answer and Explanation

Human Immunodeficiency Virus-1 (HIV-1) primarily infects T-helper lymphocytes, leading to immune system collapse in AIDS. This SEO-optimized guide explains the correct answer for the MCQ on HIV-1 infected cell types, with detailed breakdowns of all options.

Correct Answer

The correct answer is (A) T-helper lymphocytes. HIV-1 specifically targets CD4+ T-helper cells (also called CD4 T cells) via its gp120 envelope protein binding to the CD4 receptor and a co-receptor like CCR5 or CXCR4. This infection causes progressive depletion of these cells, impairing immune coordination and leading to AIDS.

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Option Explanations

• (A) T-helper lymphocytes: Primary target; HIV-1 enters via CD4 receptor, replicates, and kills these cells directly or via immune-mediated lysis, reducing CD4 counts below 200/μL in advanced stages.

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• (B) T-cytotoxic lymphocytes: These CD8+ cells (CTLs) are not primary targets; they respond to HIV by killing infected cells but get functionally exhausted over time without direct infection.

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• (C) Plasma cells: Derived from B cells, they produce antibodies but lack CD4 receptors, so HIV-1 does not infect them efficiently; indirect dysfunction occurs via loss of T-helper help.

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• (D) B-lymphocytes: Express low CD4 levels and can be infected rarely, but HIV-1 mainly affects them indirectly through T-helper depletion, causing hypergammaglobulinemia initially.

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