Macrophages are first seen in the fetal intestine at 11-12 wk and rapidly increase in number during the 12- to 22-wk period of gestation. The development of macrophage populations in the fetal intestine precedes the appearance of lymphocytes and neutrophils and does not require the presence of dietary or microbial antigens. In this study, we investigated the role of chemerin, a recently discovered, relatively selective chemoattractant for macrophages, in the recruitment of macrophage precursors to the fetal intestine. Chemerin mRNA/protein expression was measured in jejunoileal tissue from 10- to 24-wk human fetuses, neonates operated for intestinal obstruction, and adults undergoing bariatric surgery. The expression of chemerin in intestinal epithelial cells (IECs) was confirmed by using cultured primary IECs and IEC-like cell lines in vitro. The regulatory mechanisms involved in chemerin expression were investigated by in silico and immunolocalization techniques. IECs in the fetal, but not mature, intestine express chemerin. Chemerin expression peaked in the fetal intestine at 20-24 wk and then decreased to original low levels by full term. During the 10- to 24-wk period, chemerin accounted for most of the macrophage chemotactic activity of cultured fetal IECs. The maturational changes in chemerin expression correlated with the expression of retinoic acid receptor-beta in the intestine. Chemerin is an important mediator of epithelial-macrophage cross talk in the fetal/premature, but not in the mature, intestine. Understanding the regulation of the gut macrophage pool is an important step in development of novel strategies to boost mucosal immunity in premature infants and other patient populations at risk of microbial translocation.

CXC chemokines with a glutamate-leucine-arginine (ELR) tripeptide motif (ELR؉ CXC chemokines) play an important role in leukocyte trafficking into the tissues. For reasons that are not well elucidated, circulating leukocytes are recruited into the tissues mainly in small vessels such as capillaries and venules. Because ELR ؉ CXC chemokines are important mediators of endothelial-leukocyte interaction, we compared chemokine expression by microvascular and aortic endothelium to investigate whether differences in chemokine expression by various endothelial types could, at least partially, explain the microvascular localization of endothelial-leukocyte interaction. Both in vitro and in vivo models indicate that ELR ؉ CXC chemokine expression is higher in microvascular endothelium than in aortic endothelial cells. These differences can be explained on the basis of the preferential activation of endothelial chemokine production by low intensity shear stress. Low shear activated endothelial ELR ؉ CXC chemokine production via cell surface heparan sulfates, ␤ 3 -integrins, focal adhesion kinase, the mitogen-activated protein kinase p38␤, mitogen-and stress-associated protein kinase-1, and the transcription factor.

Interleukin-8 (IL-8/CXCL8) is widely expressed in fetal tissues although inflammatory changes are not seen. Circulating IL-8 is comprised of an endothelial-derived 72 correlates with a maturational increase in the neutrophil chemotactic potency of plasma IL-8. The emergence of [ser-IL-8] 72 as the major isoform is likely due to increased plasma 77 -convertase activity and/or changes in the cellular sources of IL-8. Developmental changes in IL-8 isoforms may serve to minimize its inflammatory effects in the fetus and also provide a mechanism to restore its full activity after birth.

Anesthetic induction in pediatric patients can safely be performed using multiple modalities but requires a multifaceted review and discussion with the patient and the patient’s parents or legal guardians. Intravenous (IV), intramuscular (IM), rectal, and inhaled anesthetics are all options for pediatric anesthetic induction; however, the technique chosen should be based on review of patients’ medical, surgical, and anesthetic histories; physical examination findings; and the planned procedure. The thorough review of patients’ histories and discussions with their families will not only facilitate rapport between the anesthesiologist and the aforementioned parties, but also provide information that may aid in early identification and treatment of complications associated with induction.