Expression pattern of CXCR3, CXCR4, and CCR3 chemokine receptors in the developing human brain

Chemokine receptors are essential components of the immune and central nerv ous systems, but little is known about their distribution during developmen t. We evaluated the distribution of 3 chemokine receptors: CXCR3, CXCR4, an d CCR3 in the human developing brain. Of these, CXCR3 was the only receptor expressed in fetal brain at 26 wk of gestation and its expression was rest ricted to glial cells, endothelial cells, and the choroid plexus. Neuronal staining was only seen at term in the Purkinje cells of the cerebellum. CCR 3 appeared only at term in both neurons and glial cells. The expression pat tern of these 2 receptors in the late gestation and term resembled that of adults. CXCR4 could not be detected in the fetal brain on neurons nor on gl ial cells. By examining pediatric cases, we determined that CXCR4 expressio n commences sometimes between 3.5 and 4.5 yr. Two of the chemokine receptor s examined. CCR3 and CXCR3, can be used as co-receptor together with CD4 fo r HIV entry, but neither was expressed during the second trimester of pregn ancy. Our findings suggest that it is unlikely that CCR3 or CXCR4 play a ma jor role in HIV-1 transmission in the fetal brain before 37 wk of gestation .