Which immune cells are primarily responsible for recognizing and destroying infected host cells?

Natural killer cells play a crucial role in the immune response, specifically in the recognition and destruction of infected host cells. They are a type of lymphocyte that can identify cells harboring intracellular pathogens, such as viruses. Once they detect these infected cells, natural killer cells can directly induce apoptosis, or programmed cell death, effectively eliminating the threat.

The capacity of natural killer cells to target and kill infected cells without the need for prior sensitization to the pathogen makes them a rapid and essential component of the innate immune system. They perform this function through a combination of activating and inhibitory receptors that assess the expression of stress ligands on the surface of infected or transformed cells. When these receptors detect abnormal signals, natural killer cells release cytotoxic substances that lead to the destruction of the infected cells.

This function is particularly important in the early stages of infection, prior to the adaptive immune response becoming fully activated, thus bridging the innate and adaptive immune systems. In summary, the primary responsibility of natural killer cells is to recognize and directly eliminate infected host cells, establishing them as a critical line of defense in immune surveillance.