What is the primary role of natural killer (NK) cells in the immune response?

• A. To enhance antibody production
• B. To identify and destroy infected or cancerous cells
• C. To activate T-cells
• D. To produce histamines

Answer: (B)

Natural killer (NK) cells play a crucial role in the immune response primarily by identifying and destroying infected or cancerous cells. They are a type of lymphocyte that responds quickly to virally infected cells and tumors, serving as a first line of defense in the innate immune system. NK cells recognize stressed cells in the absence of antibodies and MHC (Major Histocompatibility Complex) class restrictions, which allows them to act more rapidly than adaptive immune cells.

When NK cells encounter a target cell, they can induce apoptosis (programmed cell death) through the release of cytotoxic granules containing perforin and granzymes. This process helps to eliminate infected or malignant cells before a more specific adaptive immune response, such as T-cell activation, is initiated. The ability to detect and destroy compromised cells is vital in preventing the spread of infections and controlling tumor growth.

While other immune cells also have important functions—such as activating T-cells or producing histamines—these tasks are not the primary role of NK cells. Their specific function in recognizing and eliminating threatened cells is what distinguishes them within the immune system.