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HIV tropism — The HIV virus primarily infects which cell population in humans?

Difficulty: Easy

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).

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