Which white blood cell is primarily responsible for the nonspecific killing of tumor cells?

Natural killer (NK) cells play a crucial role in the immune system's defense against tumors and virally infected cells. These lymphocytes are key components of the innate immune response, which is characterized by its nonspecific nature. NK cells have the ability to recognize and eliminate cells that are stressed, abnormal, or transformed, including cancerous cells, without the need for prior sensitization or activation.

One of the hallmark features of NK cells is their use of activating receptors that interact with specific ligands on target cells. When they detect these abnormal cells, NK cells can induce apoptosis (programmed cell death) through the release of cytotoxic granules containing perforin and granzymes. This process contributes significantly to the elimination of tumors in the early stages of cancer development.

In contrast, other white blood cells such as neutrophils, B cells, and T cells have different roles in immune responses. Neutrophils primarily target bacterial infections and facilitate phagocytosis and inflammation. B cells are primarily involved in the adaptive immune response by producing antibodies to fight off specific pathogens. T cells, especially cytotoxic T cells, are crucial for a targeted immune response against infected or malignant cells but usually require prior exposure to the antigen.

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