Regulation of CD44 isoform expression and CD44-mediated signaling in human dendritic cells.

Dendritic cells (DCs) express CD44, a cell surface receptor for the extracellular matrix ligand hyaluronate, involved in cell-cell interactions and cell migration. Besides the "standard" form of CD44, a variety of splice variants contain an additional extracellular region encoded by 10 "variable" exons termed v1 to v10. The standard form of CD44 as well as variants containing exon v6 (CD44v6) are known to play important roles in the immune system, yet largely unexplored in the DC lineage. In this study, we examined the regulation of CD44 isoforms in human DCs derived from monocytes cultivated in the presence of GM-CSF and IL-4. We found that v3, v6 and v9 variants are all up-regulated upon TNF-alpha stimulation of DCs. In addition, we show that stimulation of DCs using anti-CD44 mAbs can induce DC agregation, up-regulation of accessory molecule expression and secretion of cytokines. A mAb directed against CD44v6 variants was shown to mediate some of these effects.