Ly49

Article summary

Ly49 is a family of membrane C-type lectin-like receptors expressed mainly on NK cells but also on other immune cells (some CD8+ and CD3+ T lymphocytes, intestinal epithelial lymphocytes (IELs), NKT cells, uterine NK cells (uNK) cells, macrophages or dendritic cells). Their primary role is to bind MHC-I molecules to distinguish between self healthy cells and infected or altered cells. Ly49 family is coded by Klra gene cluster and include genes for both inhibitory and activating paired receptors, but most of them are inhibitory. Inhibitory Ly49 receptors play a role in the recognition of self cells and thus maintain self-tolerance and prevent autoimmunity by suppressing NK cell activation. On the other hand, activating receptors recognise ligands from cancer or viral infected cells (induced-self hypothesis) and are used when cells lack or have abnormal expression of MHC-I molecules (missing-self hypothesis), which activate cytokine production and cytotoxic activity of NK and immune cells. Ly49 receptors are expressed in some mammals including rodents, cattle and some primates but not in humans. Only one human gene homologous to rodent Ly49 receptors is found in the human genome, KLRA1P (LY49L), however, it represents a non-functional pseudogene. However killer cell immunoglobulin-like receptors (KIR) have the same function in humans.…

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