title: Eotaxin is required for the baseline level of tissue eosinophils.
abstract: Eotaxin is an eosinophil-selective chemokine that is constitutively expressed in a variety of organs such as the intestine. Previous studies have demonstrated that the recruitment of eosinophils during inflammation is partially dependent on eotaxin, but the function of constitutive eotaxin during homeostasis has not been examined. To elucidate the biological role of this molecule, we now examine tissue levels of eosinophils in healthy states in wild-type and eotaxin-deficient mice. The lamina propria of the jejunum of wild-type mice is demonstrated to express eotaxin mRNA, but not mRNA for the related monocyte chemoattractant proteins. Wild-type mice contained readily detectable eosinophils in the lamina propria of the jejunum. In contrast, mice genetically deficient in eotaxin had a large selective reduction in the number of eosinophils residing in the jejunum. The reduction of tissue eosinophils was not limited to the jejunum, because a loss of thymic eosinophils was also observed in eotaxin-deficient mice. These studies demonstrate that eotaxin is a fundamental regulator of the physiological trafficking of eosinophils during healthy states. Because a variety of chemokines are constitutively expressed, their involvement in the baseline trafficking of leukocytes into nonhematopoietic tissue should now be considered.
authors.affiliation: Division of Pulmonary Medicine, Allergy, and Clinical Immunology, Children's Hospital Medical Center, Cincinnati, OH 45229, USA.
authors.forename: A N
authors.initials: AN
authors.lastname: Matthews
authors.forename: D S
authors.initials: DS
authors.lastname: Friend
authors.forename: N
authors.initials: N
authors.lastname: Zimmermann
authors.forename: M N
authors.initials: MN
authors.lastname: Sarafi
authors.forename: A D
authors.initials: AD
authors.lastname: Luster
authors.forename: E
authors.initials: E
authors.lastname: Pearlman
authors.forename: S E
authors.initials: SE
authors.lastname: Wert
authors.forename: M E
authors.initials: ME
authors.lastname: Rothenberg
mesh_terms: D000818:Animals; D001772:Blood Cell Count; D054413:Chemokine CCL11; D019742:Chemokines, CC; D002631:Chemotactic Factors, Eosinophil / Q000235:genetics*; D016207:Cytokines / Q000172:deficiency* / Q000235:genetics; D004804:Eosinophils / Q000166:cytology* / Q000502:physiology*; D017403:In Situ Hybridization; D007583:Jejunum / Q000166:cytology / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D012333:RNA, Messenger / Q000032:analysis
chemical_list: C515457:Ccl11 protein, mouse; D054413:Chemokine CCL11; D019742:Chemokines, CC; D002631:Chemotactic Factors, Eosinophil; D016207:Cytokines; D012333:RNA, Messenger