Modulation of CXC Chemokine Receptor Expression and Function in Human Neutrophils during Aging In Vitro Suggests a Role in Their Clearance from Circulation

Figure 3

Potential function of CXC chemokine receptors in human neutrophils during aging in vivo. In this model of the putative function of CXC chemokine receptors in aging human neutrophils, the increased expression of CXCR4 in senescent cells circulating in the peripheral blood (PB) is paralleled by loss of CXCR2, resulting in migration to sites with a high SDF-1 concentration such as the bone marrow (BM) or alternatively to other sites of neutrophil sequestration, where they undergo degradation. Similar to in vivo observations in the mouse, CXCR2 might also contribute the release of human neutrophils from the bone marrow. Both IL-8 receptors, CXCR1 and particularly CXCR2, may contribute to extravasation of PMN. In the tissue, further migration toward areas of inflammation (inflamm.) is still mediated by CXCR1 together with CXCR4, even when the process of aging has already started.