Final answer:
Natural Killer (NK) cells are lymphocytes that spontaneously attack developing tumor cells by recognizing and eliminating cells without “self” proteins or with abnormal markers. T cells also play a role in combating tumors, particularly when genetically modified in advanced cancer therapies.
Step-by-step explanation:
The lymphocytes that spontaneously attack developing tumor cells are known as Natural Killer (NK) cells. NK cells are a critical component of the innate immune system. They possess the ability to recognize and eliminate cells that do not express normal “self” proteins on their plasma membrane - a hallmark of many cancer cells. Moreover, these cells can respond to cells with foreign or abnormal markers, such as cells infected with viruses or cells with atypical surface proteins. NK cells accomplish this by scanning for altered expression of major histocompatibility complex (MHC) I molecules. When a discrepancy is detected, NK cells can induce apoptosis in these abnormal cells, including tumor cells, thereby inhibiting their uncontrollable division and invasion of other tissues.
Aside from NK cells, T lymphocytes (also known as T cells) also contribute to the immune defense against tumors. T cells provide cell-mediated immunity, physically attacking foreign or diseased cells. In certain advanced therapies, T cells from a cancer patient’s blood are genetically engineered to express chimeric antigen receptors (CARs) that specifically target cancer cell antigens, and are then reintroduced into the patient to combat the cancer directly.