Differentiation of monocytes into dendritic cells in a model of transendothelial trafficking

Secondary Lymphoid-Tissue Chemokine (SLC) Is Chemotactic for Mature Dendritic Cells

Dendritic cells (DC) take up antigen from the periphery and migrate to the lymphoid organs where they present the processed antigens to T cells. The propensity of DC to migrate changes during DC maturation and is probably dependent on alterations in the expression of chemokine receptors on the surface of DC. Secondary lymphoid tissue chemokine (SLC), a recently discovered chemokine for naı̈ve T cells, is primarily expressed in secondary lymphoid organs and may be important for colocalizing T cells with other cell types important for T-cell activation. We show here that SLC is a potent chemokine for mature DC but does not act on immature DC. SLC also induced calcium mobilization specifically in mature DC. SLC and Epstein-Barr virus–induced molecule 1 ligand chemokine completely cross-desensitized the calcium response of each other, indicating that they share similar signaling pathways in DC. The finding that SLC is a potent chemokine for DC as well as naı̈ve T cells suggests that it plays a role in colocalizing these two cell types leading to cognate T-cell activation.

Developmental regulation of dendritic cell function

1998 saw key advances in our understanding of the molecular mechanisms whereby immature dendritic cells recognise foreign pathogens in tissues and are induced to migrate to secondary lymphoid organs. In particular, there have been some key insights into how dendritic cells subsequently direct the evolution of immune responses by differential expression of co-stimulatory molecules.

Secondary Lymphoid-Tissue Chemokine (SLC) Is Chemotactic for Mature Dendritic Cells

Dendritic cells (DC) take up antigen from the periphery and migrate to the lymphoid organs where they present the processed antigens to T cells. The propensity of DC to migrate changes during DC maturation and is probably dependent on alterations in the expression of chemokine receptors on the surface of DC. Secondary lymphoid tissue chemokine (SLC), a recently discovered chemokine for naı̈ve T cells, is primarily expressed in secondary lymphoid organs and may be important for colocalizing T cells with other cell types important for T-cell activation. We show here that SLC is a potent chemokine for mature DC but does not act on immature DC. SLC also induced calcium mobilization specifically in mature DC. SLC and Epstein-Barr virus–induced molecule 1 ligand chemokine completely cross-desensitized the calcium response of each other, indicating that they share similar signaling pathways in DC. The finding that SLC is a potent chemokine for DC as well as naı̈ve T cells suggests that it plays a role in colocalizing these two cell types leading to cognate T-cell activation.

Dendritic cells: expansion and differentiation with hematopoietic growth factors

Dendritic cells are critical initiators of immune responses mediated by T and B lymphocytes. Dendritic cells process antigens captured in the periphery, then emigrate to lymphoid organs. There they complete their maturation by upregulating important accessory molecules and secreting cytokines, all of which support potent stimulation of antigen-specific lymphocytes. These lymphocytes return to the periphery to complete the immune response. Investigators have discovered culture systems that use exogenous hematopoietic cytokines to support the growth, differentiation, and maturation of dendritic cells in larger numbers and greater purity than was ever before possible. This has rendered dendritic cells accessible to detailed experimental evaluations and clinical applications. Dendritic cells provide a powerful means of controlling both normal and pathologic immunity.

Reciprocal control of T helper cell and dendritic cell differentiation

It is not known whether subsets of dendritic cells provide different cytokine microenvironments that determine the differentiation of either type-1 T helper (TH1) or TH2 cells. Human monocyte (pDC1)-derived dendritic cells (DC1) were found to induce TH1 differentiation, whereas dendritic cells (DC2) derived from CD4+CD3-CD11c- plasmacytoid cells (pDC2) induced TH2 differentiation by use of a mechanism unaffected by interleukin-4 (IL-4) or IL-12. The TH2 cytokine IL-4 enhanced DC1 maturation and killed pDC2, an effect potentiated by IL-10 but blocked by CD40 ligand and interferon-gamma. Thus, a negative feedback loop from the mature T helper cells may selectively inhibit prolonged TH1 or TH2 responses by regulating survival of the appropriate dendritic cell subset.