HIV tropism — The HIV virus primarily infects which cell population in humans?
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ABrain neurons as the dominant target
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BCells of the immune system (e.g., CD4 T cells, macrophages, dendritic cells)
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CMature red blood cells in circulation
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DHepatocytes (liver parenchymal cells) as the main target
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ESkeletal muscle fibers as the main target
Answer
Correct Answer: Cells of the immune system (e.g., CD4 T cells, macrophages, dendritic cells)
Explanation
Introduction:Human immunodeficiency virus (HIV) causes progressive immune deficiency by targeting key immune cells. Recognizing the primary cellular targets explains both pathogenesis and clinical vulnerability to opportunistic infections.
Given Data / Assumptions:
- HIV entry requires CD4 along with coreceptors such as CCR5 or CXCR4.
- CD4 is expressed on helper T cells and subsets of macrophages and dendritic cells.
- RBCs lack nuclei and CD4, making them non-permissive for HIV infection.
Concept / Approach:Match viral receptor usage (CD4 plus coreceptors) to host cell types to identify the primary infected populations that drive immunodeficiency.
Step-by-Step Solution:
1) Identify cells expressing CD4: helper T cells, macrophages, dendritic cells.2) Recognize that coreceptor usage determines tissue tropism (CCR5, CXCR4).3) Conclude immune cells are the main targets, explaining CD4 T-cell depletion.Verification / Alternative check:Clinical monitoring of HIV focuses on CD4 T-cell counts and viral load; antiretroviral therapy restores CD4 levels by suppressing replication in these cell types.
Why Other Options Are Wrong:
a,d,e) While HIV can affect other tissues indirectly, the primary replication sites are immune cells.c) RBCs lack nuclei and CD4; they are not infected.Common Pitfalls:Assuming any cell can be infected; overlooking receptor/coreceptor requirements for viral entry.
Final Answer:Cells of the immune system (CD4 T cells, macrophages, dendritic cells).