Receptors low affinity

NK cells are a subset of lymphocytes found in blood and lymphoid tissues, especially the spleen. They are about 15 an in diameter, possess a kidney-shaped nucleus and have two or three large granules in the cytoplasm. They are derived from the bone marrow. NK cells have the ability to kill certain tumour lines and normal cells infected by virus. Killing by NK cells is not specific for viral antigenic epitopes, and is not restricted by MHC molecules. They do not possess CD3 but do express CD2, CD 16 and CD56, together with a low-affinity receptor for the Fc portion of IgG. 

Fc,RI High affinity receptor for IgE Fc,RII Low affinity receptor for IgE FcR Receptor for Fc region of antibody... 

In contrast to the enhanced receptor expression that occurs during activation and priming, the expression of some receptors actually decreases during this process. This is particularly evident with receptors such as CD16 (the low-affinity receptor for IgG) and the ligand that binds monoclonal antibody 31D8 (a surface molecule of undefined nature whose expression is closely linked to fMet-Leu-Phe responsiveness). These molecules are GPI-linked and are shed from the cell surface during activation (see Fig. 3.10). 

Most neurotrophin-sensitive cells express two receptor types on their surface a high-affinity receptor, which appears to mediate most/all of the biological actions of the neurotrophins, and a low-affinity receptor. The high-affinity receptors are all members of a family of tyrosine kinases (the Trks). They are similar to the receptors of many other growth factors, but are expressed almost exclusively on neuronal tissue. 

When IL-2 binds to high-affinity receptors, it becomes internalized following receptor-mediated endocytosis. After high-affinity binding, there is an increase in the stimulation of phosphoinositol turnover, redistribution of protein kinase C from the cytoplasm to the cell membrane, and an increased expression of IL-2 receptors, with low-affinity receptors being preferentially increased. 

Ah receptor (AHR) A protein coded for by a gene of the Ah locus. The initial location of the Ah receptor is believed to be in the cytosol and, after binding to a ligand such as TCDD, is transported to the nucleus. Binding of aromatic hydrocarbons to the Ah receptor of mice is a prerequisite for the induction of many xenobiotic metabolizing enzymes, as well as for two responses to TCDD epidermal hyperplasia and thymic atrophy. Ah-responsive mice have a high-affinity receptor, whereas the Ah-nonresponsive mice have a low-affinity receptor. 

J Schlessmger, I. Lax, and M. Lemmon. Regulation of growth factor activation by proteoglycans what is the role of the low affinity receptors Cell, 83 (3), 357-360, 1995. 

Beavil, A.J., Edmeades, R.L., Gould, H.J. and Sutton, B.J. (1992). cr-Helical coiled-coil stalks in the low-affinity receptor for IgE (Fc epsilon RII/CD23) and related C-type lectins. Proc. Natl. Acad. Sci. USA 89, 753-757. 

The ot-chain (IL 2Ra, CD25), originally called Tac (T activation), is a 55-kDa polypeptide (also named p55) that is a low-affinity receptor (1Q= 10 M). Cells that only express this receptor show detectable biological response to IL-2, IL-2Ra is not found on resting T cells, but it is efficiently induced by T-cell activation. A site on the IL-2B a-hehx is thought to bind to the p55 receptor. ... 

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