Differential regulation of monocyte cytokine release by αV and β(2) integrins that bind CD23.

The human soluble CD23 (sCD23) protein displays highly pleiotropic cytokine-like activity. Monocytic cells express the sCD23-binding integrins αVβ(3), αVβ(5), αMβ(2) and αXβ(2), but it is unclear which of these four integrins most acutely regulates sCD23-driven cytokine release. The hypothesis that ligation of different sCD23-binding integrins promoted release of distinct subsets of cytokines was tested. Lipopolysaccharide (LPS) and sCD23 promoted release of distinct groups of cytokines from the THP-1 model cell line. The sCD23-driven cytokine release signature was characterized by elevated amounts of RANTES (CCL5) and a striking increase in interleukin-8 (IL-8; CXCL8) secretion, but little release of macrophage inflammatory protein 1β (MIP-1β; CCL4). Antibodies to αVβ(3) or αXβ(2) both promoted IL-8 release, consistent with the sCD23-driven pattern, but both also evoked strong MIP-1β secretion; simultaneous ligation of these two integrins further increased cytokine secretion but did not alter the pattern of cytokine output. In both model cell lines and primary tissue, integrin-mediated cytokine release was more pronounced in immature monocyte cells than in mature cells. The capacity of anti-integrin monoclonal antibodies to elicit a cytokine release response is epitope-dependent and also reflects the differentiation state of the cell. Although a pattern of cytokine release identical to that provoked by sCD23 could not be elicited with any individual anti-integrin monoclonal antibody, αXβ(2) and αVβ(3) appear to regulate IL-8 release, a hallmark feature of sCD23-driven cytokine secretion, more acutely than αMβ(2) or αVβ(5).