What lymphocytes function as part of the innate immunity to defend against intracellular pathogens?
The correct answer and explanation is:
The lymphocytes that function as part of the innate immunity to defend against intracellular pathogens are natural killer (NK) cells.
Explanation:
Natural killer cells are a type of lymphocyte that play a key role in the body’s innate immune response, particularly in recognizing and eliminating cells infected by intracellular pathogens like viruses or certain bacteria. Unlike other lymphocytes such as T cells and B cells, which are part of the adaptive immune system, NK cells operate without the need for prior exposure to the pathogen. This means that they can immediately respond to infected or stressed cells.
NK cells identify infected cells through changes in the surface markers of these cells. Healthy cells typically express certain molecules, such as MHC (Major Histocompatibility Complex) class I, which help the immune system differentiate between self and non-self cells. However, when a cell becomes infected with a virus or transformed by cancer, it often downregulates or loses these MHC class I molecules. NK cells recognize this loss and bind to these cells, triggering their destruction.
NK cells are equipped with cytotoxic granules that contain enzymes like perforin and granzymes. Perforin forms pores in the target cell’s membrane, allowing granzymes to enter the cell and induce apoptosis (programmed cell death). Additionally, NK cells can release cytokines like interferon-gamma (IFN-γ) that help activate other immune cells and amplify the immune response against the pathogen.
These cells are critical for early defense against infections before the adaptive immune system can mount a more specific and long-lasting response. NK cells contribute to the overall immune surveillance, constantly monitoring for abnormal cells, including infected or tumorigenic cells, helping to contain infections and prevent their spread.