AIIMS CRE 2025: What is the normal CD8 T-cell count range?

AIIMS CRE 2025

Biochemistry and Nutrition

Easy

Appeared in: AIIMS CRE 2025

Explanation

The normal reference range for absolute CD8 T-cell count in healthy adults is typically between 300 and 1000 cells/μL.
The option 300–600 cells/μL falls squarely within this accepted normal range.
CD8 T-cells, or cytotoxic T-lymphocytes, are essential for cell-mediated immunity.
Their primary role is to identify and eliminate cells that are infected with intracellular pathogens (like viruses) or have become cancerous.

Option A: This range is significantly below the normal lower limit and indicates a state of CD8 lymphocytopenia, which implies a weakened immune system or immunosuppression.
Option C: While this range overlaps with the normal CD8 count, it represents a narrower, higher-end segment of the typical range and is less representative of the entire normal spectrum than 300-600 cells/μL.
Option D: This range represents the normal count for CD4 T-cells (helper T-cells), not CD8 T-cells. It is a common distractor in questions about lymphocyte counts.

Visual 1: Diagram: Illustrating the difference in function between a CD4 (Helper) T-cell activating other immune cells and a CD8 (Cytotoxic) T-cell directly killing an infected cell.
Visual 2: Chart: Showing the progression of CD4 and CD8 counts and the CD4:CD8 ratio over the course of an untreated HIV infection, highlighting the initial drop and subsequent inversion of the ratio.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Normal laboratory values for T-lymphocytes (CD8 T-cells) as background academic context rather than a clinical decision trigger.
Monitoring CD4 and CD8 counts is fundamental in managing patients with HIV. A low CD4 count (below 200 cells/μL) indicates severe immune suppression (AIDS) and high risk for opportunistic infections.
The CD4:CD8 ratio is a key indicator of immune dysregulation. An inverted ratio (less than 1.0) is a hallmark of HIV infection and can persist even in patients on effective antiretroviral therapy, indicating ongoing immune activation.
What if? If a patient on chemotherapy presents with a CD8 count of 150 cells/μL, the nurse should recognize this as severe lymphocytopenia, place the patient on neutropenic precautions to prevent infection, and report the critical lab value immediately, as the patient is at high risk for viral reactivations and other infections.

How to Approach the Question

First, identify the core of the question: it asks for a specific laboratory value, the normal range for CD8 T-cells.
This is a factual recall question. Access your knowledge of normal hematological values.
Evaluate each option. Recall that CD4 counts are generally higher than CD8 counts in healthy individuals.
Eliminate the range for CD4 cells (800–1200 cells/μL) as it's a common distractor.
Eliminate the range that is clearly too low and would indicate immunodeficiency (100–300 cells/μL).
Compare the remaining plausible options (300–600 and 450–750). Select the option that best represents the commonly accepted broad normal range for CD8 cells.

Concept Tested & Keywords

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E6 Textbook of Biochemistry for medical Students 11th Edition DM Vasudevan Part 2 — Subpart B (pp 240-463 of 478) p. 463-478