Effect of keratinocyte cytokines on Thy-1+ dendritic epidermal cells

Dynamics of the interaction of γδ T cells with their neighbors in vivo

γδ T cells are a diverse component of the immune system in humans and mice with presumably important but still largely unknown functions. Understanding the dynamic interaction of γδ T cells with their neighbors should help to understand their physiological role. This review addresses recent advances and strategies to visualize the dynamic interactions of γδ T cells with their neighbors in vivo. Current knowledge regarding the dynamic contacts of tissue resident γδ T cells and epithelial cells, but also of the communication between circulating γδ T cells and DCs, monocytes and FoxP3(+) regulatory T cells is revisited with emphasis on the role of γδ T cell motility.

Interleukin (IL)-15 promotes the growth of murine epidermal gamma delta T cells by a mechanism involving the beta- and gamma c-chains of the IL-2 receptor

Dendritic epidermal T cells (DETC) are skin-specific members of the epithelial gamma delta T-cell family in mice. We have reported previously that the growth of DETC is promoted by interleukin (IL)-2 in an autocrine fashion, or by IL-7, which is secreted by neighboring keratinocytes. Here we report that DETC growth is promoted by IL-15, a newly discovered T-cell growth factor that is produced in lymphoid as well as nonlymphoid tissues. Recombinant IL-15 promoted the growth of the 7-17 DETC line in a time- and dose-dependent fashion. Using monoclonal antibodies against alpha-, beta-, or gamma c-chains of the IL-2 receptor complex, we observed that the combination of anti-beta chain and anti-gamma c chain antibodies blocked IL-15 responsiveness completely, whereas anti-alpha chain had no effect. These results indicate that this gamma delta T-cell line uses the beta/gamma c heterodimer for proliferative responses to IL-15. Antibodies against IL-2 or IL-7 did not block IL-15-driven proliferation of 7-17 DETC, indicating that IL-15 promotes their growth in an IL-2- and IL-7-independent manner. Both the surface expression of beta/gamma c heterodimers and the IL-15 responsiveness of 7-17 DETC were highest 1 to 8 days after concanavalin A stimulation, and both declined substantially 21 days after stimulation, illustrating regulation by the state of cell activation. Working with epidermal cells that were freshly procured from CBA mice, we noted that IL-15 promoted conavalin-A-triggered growth of Thy-1+ cells (i.e., DETC), but not of the Thy-1- cells. The gamma c-chain was not expressed by freshly procured DETC, becoming detectable within 48 h after concanavalin A stimulation. We propose that IL-15 facilitates the growth of epithelial gamma delta T cells by a beta/gamma c receptor-dependent mechanism.

Production of IL-3 by non-transformed primary neonatal murine keratinocytes: evidence for constitutive IL-3 gene expression in neonatal epidermis

Interleukin 3 (IL-3) is a cytokine produced by activated T lymphocytes that is best understood as a hematopoietic growth and differentiation factor. Production of IL-3 by other cell types is controversial; while certain transformed non-lymphocyte cell lines can produce IL-3, it is generally assumed that their non-transformed counterparts do not. It has been previously reported that Pam 212, a transformed murine keratinocyte cell line, produces IL-3. In this study we report that IL-3 can also be secreted by normal murine keratinocytes. Using a cell line (FL5.12) which is responsive to IL-3 and not to other keratinocyte derived cytokines, (e.g. GM-CSF, IL-1 and IL-6), we tested conditioned media from cultures of normal neonatal keratinocytes for biologically active IL-3. These media stimulated the proliferation of FL5.12, and the effect could be neutralized by specific antibodies to IL-3. The presence of IL-3 mRNA was demonstrated by polymerase chain reaction (PCR) amplification of reverse transcribed IL-3 mRNA from cultured normal neonatal keratinocytes and confirmed by Southern blot analysis. By similar techniques, IL-3 mRNA could be identified in freshly isolated neonatal epidermis but not dermis. These data indicated that IL-3 is produced by keratinocytes in the skin of normal neonatal mice, raising the likelihood that the neonatal epidermal microenvironment may have hematopoietic or lymphopoietic properties.