INTERFERON-ALPHA INDUCES THE EXPRESSION OF THE L-SELECTIN HOMING RECEPTOR IN HUMAN B-LYMPHOID CELLS

The L-selectin homing receptor expressed by lymphocytes mediates the initial attachment of these cells to high endothelial venules within peripheral lymph nodes. This adhesive interaction is required for the migration of B and T lymphocytes from the blood into peripheral lymph nodes. There is currently little information regarding the nature of the factors involved in the regulation of the synthesis and expression of L-selectin by lymphocytes. In this report, the immunomodulatory cytokine interferon-alpha (IFN-alpha) was shown to markedly upregulate the surface density of L-selectin in the established human B lymphoid Daudi cell line and in a subpopulation of tissue-derived human B lymphoid cells. Other cytokines such as EFN-gamma, tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-2, IL-4, IL-6, and low molecular weight B cell growth factor did not affect L-selectin surface expression in the model Daudi B cell line. Upregulation of L-selectin surface density in IFN-alpha-treated Daudi B cells correlated directly with an increase in L-selectin mRNA steady state levels and enhanced L-select-independent binding to a carbohydrate-based ligand, phosphomonoester core polysaccharide. Regulation of L-selectin mRNA by EFN-alpha had characteristics similar to that of classical IFN-stimulated genes including rapid kinetics of induction, protein-synthesis-independent induction, and sensitivity to tyrosine-kinase inhibitors. IFN-alpha did not upregulate L-selectin mRNA levels or surface expression in an IFN-resistant Daudi subclone which exhibits a defect in the signal transduction pathway required for the transcriptional induction of IFN-stimulated genes. These data demonstrate a fundamental role for IFN-alpha in regulating L-selectin synthesis and expression in human B lymphoid cells and suggest a mechanism whereby this cytokine regulates the regional trafficking of B cells to peripheral lymph nodes.