<unk> s, also known as<unk> s or large granular lymphocytes (LGL), are a type of cytotoxic lymphocyte critical to the innate immune system that belong to the rapidly expanding family of innate lymphoid<unk> s (ILC) and represent 5–20% of all circulating lymphocytes in humans. The role of<unk> s is analogous to that of cytotoxic T<unk> s in the vertebrate adaptive immune response.<unk> s provide rapid responses to virus-infected<unk>  and other intracellular pathogens acting at around 3 days after infection, and respond to tumor formation. Typically, immune<unk> s detect the major histocompatibility complex (MHC) presented on infected<unk>  surfaces, triggering cytokine release, causing the death of the infected<unk>  by lysis or apoptosis.<unk> s are unique, however, as they have the ability to recognize and kill stressed<unk> s in the absence of antibodies and MHC, allowing for a much faster immune reaction. They were named<unk>  killers" because of the notion that they do not require activation to kill<unk> s that are missing "self" markers of MHC class 1. This role is especially important because harmful<unk> s that are missing MHC I markers cannot be detected and destroyed by other immune<unk> s, such as T lymphocyte<unk> s.<unk> s can be identified by the presence of CD56 and the absence of CD3 (CD56+, CD3−).<unk> s (belonging to the group of innate lymphoid<unk> s) are one of the three kinds of<unk> s differentiated from the common lymphoid progenitor, the other two being B and T lymphocytes.<unk> s are known to differentiate and mature in the bone marrow, lymph nodes, spleen, tonsils, and thymus, where they then enter into the circulation.<unk> s differ from<unk>  killer T<unk> s <unk> Ts) phenotypically, by origin and by respective effector functions; often,<unk>  activity promotes<unk>  activity by secreting interferon gamma. In contrast to<unk> s,<unk> s do not express T-cell antigen receptors (TCR) or pan T marker CD3 or surface immunoglobulins (Ig) B<unk>  receptors, but they usually express the surface markers CD16 (FcγRIII) and CD57 in humans,<unk> 1.1 or<unk> 1.2 in C57BL/6 mice. The<unk> p46<unk>  surface marker constitutes, at the moment, another<unk>  marker of preference being expressed in both humans, several strains of mice (including BALB/c mice) and in three common monkey species. In addition to<unk> s being effectors of innate immunity, both activating and inhibitory<unk>  receptors play important functional roles, including self tolerance and the sustaining of<unk>  activity.<unk> s also play a role in the adaptive immune response: numerous experiments have demonstrated their ability to readily adjust to the immediate environment and formulate antigen-specific immunological memory, fundamental for responding to secondary infections with the same antigen. The role of<unk> s in both the innate and adaptive immune responses is becoming increasingly important in research using<unk>  activity as a potential cancer therapy.
Natural killer cell
Natural killer T cell
T cell
Cytokine-induced killer cell
Dendritic cell
Reactive lymphocyte
Mast cell
Monocyte