Cell mediated immunity is achieved by?

AIIMS Bhuvneshwar NO- 2018

Applied Physiology

Easy

Appeared in: AIIMS Bhuvneshwar NO- 2018

Explanation

Cell-mediated immunity (CMI) is a type of adaptive immune response mediated directly by T lymphocytes (T cells), not by antibodies.
T cells recognize and act against intracellular pathogens (like viruses and some bacteria), tumor cells, and foreign grafts.
Helper T cells (CD4+) coordinate the immune response by activating other cells, such as macrophages.
Cytotoxic T cells (CD8+) directly recognize and kill infected host cells or tumor cells, eliminating the source of the problem.

Option A: B cells are the primary cells of humoral immunity. They differentiate into plasma cells which produce and secrete antibodies.
Option C: Eosinophils are granulocytes of the innate immune system, not the adaptive immune system. Their main role is to combat parasitic infections and they are involved in allergic reactions.
Option D: Neutrophils are phagocytic cells of the innate immune system. They are first responders to acute bacterial infections but are not the primary mediators of the specific, long-term memory associated with cell-mediated immunity.

Visual 1: Diagram: A flowchart comparing the pathways of humoral immunity (B cells → plasma cells → antibodies) and cell-mediated immunity (T cells → helper/cytotoxic T cells → direct cell killing/activation of other cells).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Cell-Mediated vs. Humoral Immunity as background academic context rather than a clinical decision trigger.
Understanding CMI is crucial for managing diseases caused by intracellular pathogens like Mycobacterium tuberculosis and viruses such as HIV, where a strong T-cell response is essential for control.
CMI is the primary mechanism behind transplant rejection, where the recipient's T cells recognize the donor organ's cells as foreign and attack them. Immunosuppressive drugs often target T-cell activation.
What if? If a patient has a deficient T-cell count (as in Acquired Immunodeficiency Syndrome - AIDS), they become highly susceptible to opportunistic infections (like Pneumocystis pneumonia) and certain cancers. This is because their cell-mediated immunity is compromised, even if their antibody levels (humoral immunity) are initially normal.

How to Approach the Question

This is a factual recall question from the topic of immunology.
First, identify the core concept in the question: 'Cell-mediated immunity'.
Recall the two main branches of adaptive immunity: humoral and cellular (cell-mediated).
Associate humoral immunity with B cells and antibodies, which circulate in body fluids ('humors').
Associate cell-mediated immunity with T cells, which act directly on other cells.
Evaluate the options based on this core knowledge: B cells are for humoral immunity, while Eosinophils and Neutrophils are part of the innate immune system. This process of elimination leaves T cells as the correct answer.

Concept Tested & Keywords

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