The cell which is primarily responsible for immunity to intracellular viruses, tumor cells, and fungi is- .

RRB Nsg. Superintendent -29 April-2025 (shift-2nd)

Applied Microbiology & Infection control

Medium

Appeared in: RRB Nsg. Superintendent -29 April-2025 (shift-2nd)

Explanation

T Lymphocytes are the primary effector cells of cell-mediated immunity (CMI).
CMI is the body's main defense against pathogens that live and replicate inside host cells (intracellular), as well as against tumor cells and fungi.
T Lymphocytes include different subsets: T Helper cells (CD4+) are crucial for activating immune responses against fungi, while T Cytotoxic cells (CD8+) directly kill virus-infected and tumor cells.
Because the question includes viruses, tumors, and fungi, the broader category of T Lymphocytes is the most complete answer, as it encompasses the cells responsible for all three.

Option A: Natural Killer (NK) cells are part of the innate immune system, not the adaptive system. While they do kill tumor and virus-infected cells, they are non-specific and are not considered the primary, targeted response, especially for fungal infections.
Option B: B Lymphocytes are responsible for humoral immunity, which involves producing antibodies. Antibodies are effective against extracellular pathogens (like bacteria in the bloodstream) but cannot reach pathogens that are already inside host cells.
Option D: T cytotoxic cells are a specific type of T lymphocyte. While they are the primary cells that kill virus-infected and tumor cells, they are not the main orchestrators of the immune response against fungi. That role falls to T helper cells.

Visual 1: Flowchart - A diagram illustrating the two branches of adaptive immunity: Humoral (B cells -> antibodies -> extracellular pathogens) and Cell-Mediated (T cells -> intracellular pathogens, tumors, fungi). This helps visualize the division of labor.
Visual 2: Diagram - An illustration showing a T cytotoxic cell binding to and destroying a virus-infected cell, and a T helper cell activating a macrophage to kill a fungus. This clarifies the different mechanisms within the T-cell family.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain The concept tested is the distinction between different types of lymphocytes and their specific roles in the adaptive immune response, particularly cell-mediated immunity as background academic context rather than a clinical decision trigger.
Understanding the role of T lymphocytes is critical in managing patients with immunodeficiencies. For example, in HIV/AIDS, the virus specifically targets and destroys CD4+ T helper cells, crippling the immune system and leaving the patient vulnerable to opportunistic infections, including fungi (like Pneumocystis jirovecii) and viruses.
What if? - If a patient is on immunosuppressive drugs after an organ transplant (which primarily target T-cell activation to prevent rejection), they become highly susceptible to the very same threats: intracellular viruses (like CMV), fungi (like Aspergillus), and certain cancers. This highlights the protective role of a functional T-cell response.
Monitoring the CD4 count is a standard practice in managing HIV patients. A low CD4 count indicates severe immune damage and a high risk of opportunistic infections.

How to Approach the Question

First, analyze the keywords in the question: 'intracellular viruses', 'tumor cells', and 'fungi'. These are the targets.
Recognize that all three targets are primarily handled by cell-mediated immunity because they are either inside cells or are abnormal host cells.
Recall the main cells of the adaptive immune system: B lymphocytes and T lymphocytes.
Associate B lymphocytes with humoral immunity (antibodies for extracellular pathogens) and T lymphocytes with cell-mediated immunity (for intracellular pathogens).
Evaluate the options. 'T Lymphocytes' is the broad category for cell-mediated immunity. 'T cytotoxic cells' is a sub-type. Since the question includes fungi (handled by T helper cells) in addition to viruses/tumors (handled by T cytotoxic cells), the most comprehensive answer is the parent category, T Lymphocytes.

Concept Tested & Keywords

Concept Tested: The concept tested is the distinction between different types of lymphocytes and their specific roles in the adaptive immune response, particularly cell-mediated immunity.
Stem keywords: cell, immunity, intracellular viruses, tumor cells, fungi
Lead-in keywords: primarily responsible

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