AP BIOLOGY

Detailed explanation-1: -NK cells are cytotoxic lymphocytes that provide systemic defense against pathogens and malignancy. Although historically considered cells of the innate immune system, NK cells are now known to be capable of memory or memory-like immune responses in certain settings.

Detailed explanation-2: -Natural killer (NK) cells target and kill aberrant cells, such as virally infected and tumorigenic cells. Killing is mediated by cytotoxic molecules which are stored within secretory lysosomes, a specialized exocytic organelle found in NK cells.

Detailed explanation-3: -Memory-like NK cells differentiate either in vitro (with IL-15 support for survival), or in vivo in NSG mice or human patients. The resultant ML NK cells exhibit flexible, enhanced responses to a variety of NK cell stimuli, including tumor targets.

Detailed explanation-4: -B lymphocytes are the cells of the immune system that make antibodies to invading pathogens like viruses. They form memory cells that remember the same pathogen for faster antibody production in future infections.