AIIMS Bhuvneshwar NO…: Cell mediated immunity is achieved by?

AIIMS Bhuvneshwar NO- 2018

Applied Microbiology & Infection control

Easy

Appeared in: AIIMS Bhuvneshwar NO- 2018

Explanation

Cell-mediated immunity (CMI) is a function of T lymphocytes (T cells), which are designed to combat pathogens that replicate inside host cells.
This response is carried out by two main types of T cells: CD4+ helper T cells and CD8+ cytotoxic T lymphocytes (CTLs).
CD4+ helper T cells secrete cytokines to activate other immune cells, like macrophages, to destroy ingested microbes.
CD8+ CTLs directly recognize and kill virus-infected cells and tumor cells, thereby eliminating the source of infection or abnormal growth.

Option A: B cells are the primary mediators of humoral immunity, not cell-mediated immunity. Their main function is to differentiate into plasma cells and produce antibodies.
Option C: Eosinophils are granulocytes of the innate immune system. Their primary role is in defense against multicellular parasites (like helminths) and in modulating allergic inflammatory responses.
Option D: Neutrophils are the most abundant type of white blood cell and are phagocytes of the innate immune system. They are first responders to acute bacterial infections.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Mediators of Cell-Mediated Immunity as background academic context rather than a clinical decision trigger.
Understanding cell-mediated immunity is crucial for nurses as it is the primary defense against intracellular pathogens like Mycobacterium tuberculosis (TB), viruses (e.g., HIV, influenza), fungi, and protozoa.
CMI is also responsible for anti-tumor immunity (cancer surveillance) and the rejection of transplanted organs, which is why transplant recipients require immunosuppressive drugs that often target T cell function.
What if a patient has a very low CD4+ T cell count, as seen in advanced HIV/AIDS? Their cell-mediated immunity is severely compromised. This makes them highly susceptible to opportunistic infections from intracellular pathogens (like Pneumocystis pneumonia, TB) and certain cancers, which a healthy immune system would normally control.

How to Approach the Question

First, identify the key concept in the question stem, which is 'cell-mediated immunity'.
Recall the two major arms of the adaptive immune system: humoral immunity and cell-mediated immunity.
Associate humoral immunity with antibodies, which circulate in the body's fluids (or 'humors'), and the B cells that produce them.
Associate cell-mediated immunity with cells that directly attack other cells. This is the primary role of T cells (T lymphocytes).
Evaluate the options: B cells are for humoral immunity. Eosinophils and neutrophils are part of the innate immune system with different functions. Therefore, T cells are the correct answer.

Concept Tested & Keywords

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E6 Pathology- ROBBINS & COTRAN PATHOLOGIC BASIS OF DISEASE 10TH Ed pp. 208-210, 210-212

E6 Medicine Harrison 22e Part 2 p. 667-669