CD4, soluble

Cluster determinant 4 (CD4), a type I transmembrane glycoprotein of the immunoglobulin family of receptors, playsan integral role in signal transduction and T-cell differentiation, development and activation. CD4 is constitutively expressed on thesurface of various immune cells, including monocytes, macrophages, eosinophils, dendritic cells, and most prominently Tlymphocytes, where it functions as an essential co-receptor and co-ligand for T-cell receptor (TCR) and major histocompatibilitycomplex class II (MHC-II) molecules. Ligation by MHC-II molecules on the surface of antigen-presenting cells can serve toinfluence adaptive immunity by facilitating helper T-cell activation and macrophage differentiation, while ligation by proinflammatorycytokine IL-16 can contribute to innate immunity by chemoattracting CD4-expressing peripheral immune cells alongan IL-16 gradient for their recruitment and activation at sites of inflammation. The protean functionality of CD4 extends pastimmunity as CD4 also notably serves as the major receptor for HIV-1 and human herpes virus 7 (HHV-7) infections. During HIVpathogenesis, CD4 acts instrumentally as a high-affinity entry receptor for the internalization of HIV-1 following binding of the viralenvelope glycoprotein gp120 to CD4’s extracellular domain. Recombinant Human sCD4 is amonomeric glycoprotein of 371 amino acid residues, which correspond to the extracellular CD4 domain, and a calculated molecularweight of 41.3 kDa. As a result of glycosylation, Recombinant Human sCD4 migrates with an apparent molecular mass of approximately 45-55 kDa by SDS-Page Gel analysis, under reducing conditions.