Which cell type is specifically identified as Natural Killer Cells?

Natural Killer (NK) Cells are specifically identified as Large Granular Lymphocytes. This classification arises from their distinctive morphology, characterized by the presence of large granules in the cytoplasm, which are packed with cytotoxic substances. NK cells play a crucial role in the immune system, specifically in the innate immune response. They are integral to the body’s defense against viral infections and tumor surveillance, capable of identifying and destroying stressed or abnormal cells without prior sensitization to them.

The large granular appearance of these cells under microscopy helps in their identification histologically, distinguishing them from the other lymphocyte types. Unlike B cells, which mature into plasma cells to produce antibodies, or T cells, which have various functions such as helping other immune cells (helper T cells) or remembering past infections (memory T cells), NK cells have a direct cytotoxic function. Their ability to recognize and kill infected or malignant cells inherently categorizes them within the subset of large granular lymphocytes, making them unique in their actions and characteristics.