Eosinophils high-affinity

The histamine H4-receptor which was discovered in 2001 has been shown to have a role in chemo-taxis and mediator release in various types of immune cells including mast cells, eosinophils, dendritic cells and T cells. H4-receptor antagonists have been shown to have anti-inflammatory properties and efficacy in a number of disease models, such as those for asthma and colitis in vivo. Cinnarizine has a high affinity for the H4-receptor. Recently other H4-receptor antagonists have been developed with high receptor affinity and specificity. The first few studies into the function of H4-receptors suggested... 

Fig. 9.3. Immunoglobulin E (IgE) and mast cell activation are important components of the mammalian response to cestode infections (ADCC, antibody dependent cell-mediated cytotoxicity Ag, antigen EO, eosinophils Feel, high affinity receptor for Fc portion of IgE LTs, leukotrienes Mac, macrophages NO, nitric oxide PGs, prostaglandins TNFa, tumour necrosis factor alpha).

FceRI is a high-affinity receptor. Apart from mast cells and basophils, it may be found on Langerhans cells, eosinophils, and monocytes. 

IgE antibodies have the unique ability to bind with high affinity to Fc<-RI receptors on mast cells and basophils, and induce degranulation and cytokine secretion by these cells when they are cross-linked by antigen. In addition to its central role in the patht nesis of atopic disorders, it has been speculated that IgE-mediated mast cell degranulation may have a role in the expulsion of gut and respiratory traa parasites. IgE may also have a role in eosinophil killing of parasites by IgE-mediated antibody-dependent cell-mediated cytotoxicity. Despite these observations, it is unclear whether IgE plays an indispensable role in protection against disease. 

Gounni, A.S., Lamkhioued, B., Tanaka, Y., Delaporte, E., Capron, A., Kinet, J.P. and Capron, M. (1994). High-affinity IgE receptor on eosinophils is involved in defence against parasites. Nature 367, 183-186. 

CCRl was the first isolated CC chernokine receptor. Originally identified as the RANTES (CCL5)/MIP-la (CCL3) receptor (62, 63), it was subsequently shovm that MCP-3 (CCL7) also binds with high affinity to CCRl (64). CCRl is expressed on various leukocyte cell types, including monocytes, T-cells, and eosinophils (see Table 4.1). In mouse, but not human, CCRl is also expressed on neutrophils (65). CCRl mRNA has also been detected in human dendritic cells (66). 

Surface FceRI expression on peripheral blood eosinophils has been variably observed in vivo since the first report of the high-affinity receptor on blood eosinophils (90) and remains a topic of controversy (91). The initial description involved blood eosinophils from subjects with hypereosinophilic syndromes (90), but subsequent studies have failed to reproduce these observations (85,92). Blood eosinophils express both mRNA and intracellular protein for the a and y subunits of the FceRI receptor complex but lack the P subunit protein. Eosinophils in culture with IL-5 release the a subunit protein into the culture supernatant, but the addition of IgE failed to induce expression of the receptor on the cell surface... 

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