The new cell that takes part in innate immunity by killing virus-infected cells is:

ESIC Nursing Officer -2019 (Shift -1)

Applied Microbiology & Infection control

Easy

Appeared in: ESIC Nursing Officer -2019 (Shift -1)

Explanation

Natural Killer (NK) cells are lymphocytes that are a crucial part of the innate immune system.
Their primary function is to provide a rapid response to viral infections and to perform tumor surveillance.
NK cells recognize and kill virus-infected cells by detecting changes in surface molecules, such as the downregulation of MHC class I molecules, without needing prior exposure to the pathogen.
This ability to act without prior sensitization is a defining characteristic of the innate immune response, distinguishing NK cells from T cells.

Option A: Neutrophils are phagocytic cells of the innate immune system, but their main role is to combat bacterial and fungal infections by engulfing them. They are not the primary cell type for killing virus-infected host cells.
Option B: T cells, specifically cytotoxic T lymphocytes (CTLs), do kill virus-infected cells, but they are part of the adaptive immune system, not the innate immune system. They require prior activation and recognition of a specific antigen.
Option D: Macrophages are phagocytes and antigen-presenting cells (APCs) in the innate immune system. While they are involved in clearing virally infected cells and debris, their primary role is not the direct, non-specific killing characteristic of NK cells.

Visual 1: Diagram - An illustration showing an NK cell binding to a virus-infected cell and releasing cytotoxic granules (perforin and granzymes) to induce apoptosis, while ignoring a healthy cell with normal MHC class I expression.
Visual 2: Flowchart - A simple flowchart distinguishing the innate immune response (rapid, non-specific, involving NK cells and macrophages) from the adaptive immune response (slower, specific, involving T cells and B cells).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Cellular components of the innate immune system and their specific functions as background academic context rather than a clinical decision trigger.
NK cells provide a critical first line of defense against viral infections, helping to control viral replication before the adaptive immune response is fully mounted.
Deficiencies in NK cell number or function (NKD) can lead to increased susceptibility to severe and recurrent viral infections, particularly from the herpesvirus family (e.g., CMV, EBV, HSV).
What if? - If a patient has a genetic defect leading to NK cell deficiency, they would be highly vulnerable to certain viral infections and some cancers. Treatment might involve antiviral prophylaxis and potentially a hematopoietic stem cell transplant to restore immune function.

How to Approach the Question

First, dissect the question to identify the key requirements: the cell must be part of (1) 'innate immunity' and its function must be (2) 'killing virus-infected cells'.
Evaluate each option against the first requirement: 'innate immunity'. This eliminates T cells, which are part of the adaptive immune system.
Next, evaluate the remaining options (Neutrophil, NK cell, Macrophage) against the second requirement: 'killing virus-infected cells'.
Recall the primary functions: Neutrophils are mainly for bacteria, and Macrophages are primarily for phagocytosis and antigen presentation.
This leaves NK cells, whose specialized role is the direct killing of virus-infected and tumor cells in a non-specific, innate manner.
Confirm this by remembering that 'Natural Killer' refers to their ability to kill target cells without prior sensitization.

Concept Tested & Keywords

Concept Tested: Cellular components of the innate immune system and their specific functions.
Stem keywords: innate immunity, killing virus-infected cells
Lead-in keywords: is
Negative lead-in flag: false

Qgkx17x47HM-4pE7NZTh1E