The INDIVIDUALIST

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Immunology

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Description

IL-5 is an interleukin produced by T helper-2 cells and mast cells. Its functions are to stimulate B cell growth and increase immunoglobulin secretion. It is also a key mediator in eosinophil activation.

Discussion

As the main regulator of eosinopoiesis, eosinophil maturation and activation, and IgA production, IL5 contributes in several ways to human immune defenses against various pathogens, including helminths and infectious agents of the digestive and respiratory tracts. On the other hand, the increase in number of eosinophils and the activation of these cells, both of which are related to elevated IL5 production, are the cause of severe pathologic disorders, as in asthma or hypereosinophilic syndromes.

Abstracts

Effect of vitamin E-bonded dialyzer on eosinophilia in haemodialysis patients

Nephrol Dial Transplant. 2005 Sep;20(9):1932-5. Epub 2005 May 26. Kojima K, Oda K, Homma H, Takahashi K, Kanda Y, Inokami T, Uchida S.

  • BACKGROUND: Eosinophilia in haemodialysis patients probably results from allergy to haemodialysis-related materials, including dialyzer membranes. We examined the effects of vitamin E-bonded dialyzers on eosinophil counts in haemodialysis patients. METHODS: We enrolled seven patients who were on regular haemodialysis and had sustained eosinophilia. White blood cell, eosinophil, CD4- and CD8-positive lymphocyte counts, and serum interleukin-5 (IL-5) and IgE levels were determined before, 2 and 4 weeks after switching to vitamin E-bonded dialyzers. RESULTS: Eosinophil and CD4-positive lymphocyte counts and serum IL-5 were significantly (P = 0.003, 0.003 and 0.031, respectively) decreased after switching to vitamin E-bonded dialyzers. CD8-positive lymphocyte counts and serum IgE levels were unaltered. Crossover tests in two cases reproduced the higher eosinophilia within 4 weeks after returning to the original non-vitamin E-bonded dialyzer. Conclusion: Vitamin E-bonded dialyzers may ameliorate eosinophilia through a mechanism mediated by a decrease in IL-5 secretion by CD4-positive lymphocytes.
Retinoic acid modulates IL-5 receptor expression and selectively inhibits eosinophil-basophil differentiation of hemopoietic progenitor cells.

J Allergy Clin Immunol. 2002 Feb;109(2):307-13. Upham JW, Sehmi R, Hayes LM, Howie K, Lundahl J, Denburg JA.

  • BACKGROUND: IL-5 plays a central role in eosinophil and basophil differentiation, exerting its effects through the IL-5 receptor (IL-5Ralpha). Currently, little is known concerning regulation of IL-5Ralpha expression in the context of commitment of hemopoietic progenitor cells to the eosinophil and basophil lineages. OBJECTIVE: Because all-trans retinoic acid (ATRA) is known to modulate some aspects of hemopoietic differentiation, we examined the effects of ATRA on eosinophil-basophil differentiation and IL-5Ralpha expression. METHODS: Progenitor cells were obtained from bone marrow aspirates and cord blood samples. Enriched populations of CD34(+) cells were isolated by means of positive immunomagnetic selection with MACS beads. RESULTS: In semisolid methylcellulose cultures of normal human bone marrow, ATRA (10(-6) mol/L) selectively suppressed eosinophil-basophil colony-forming units but had no effect on granulocyte-macrophage colony-forming units. Similarly, ATRA (10(-6) mol/L) inhibited eosinophil-basophil differentiation of cord blood CD34(+) cells in liquid culture, whereas neutrophil differentiation proceeded without impediment. Most importantly, these effects of ATRA (10(-8) to 10(-6) mol/L) on CD34(+) cells were associated with a dose-dependent inhibition of IL-5Ralpha but no change in GM-CSF receptor expression, as detected with flow cytometry. CONCLUSIONS: These findings indicate that retinoids can differentially regulate expression of IL-5Ralpha, but not GM-CSF receptor, and that these effects have functional consequences in vitro on eosinophil and basophil differentiation.

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