IMMUNOLOGY

Detailed explanation-1: -NK cells, however, are generally considered to be components of innate immune defense because they lack antigen-specific cell surface receptors.

Detailed explanation-2: -Numerous cells are involved in the innate immune response such as phagocytes (macrophages and neutrophils), dendritic cells, mast cells, basophils, eosinophils, natural killer (NK) cells and innate lymphoid cells. Phagocytes are sub-divided into two main cell types: neutrophils and macrophages.

Detailed explanation-3: -NK cells. NK cells constitute the primary innate immune cell type responsible for killing non-MHC expressing cancer cells, releasing small cytotoxic proteins such as perforin and granzyme that cause apoptosis in target cells.