The role of dendritic cells in contact hypersensitivity

Characterization of a CD44/CD122int memory CD8 T cell subset generated under sterile inflammatory conditions

Most memory CD8 T cell subsets that have been hitherto defined are generated in response to infectious pathogens. In this study, we have characterized the CD8 T cells that survive priming conditions, devoid of pathogen-derived danger signals. In both a TCR-transgenic model and a model of contact hypersensitivity, we show that the priming of naive CD8 T cells under sterile inflammatory conditions generates memory. The corresponding memory CD8 T cells can be identified by their intermediate expression levels of CD44 and CD122. We also show that CD44/122(int) memory CD8 T cells spontaneously develop in wild type mice and that they display intermediate levels of several other memory traits including functional (IFN-gamma secretion capacity, CCL5 messenger stores), phenotypic, and molecular (T-bet and eomesodermin expression levels) features. We finally show that they correspond to an early differentiation stage and can further differentiate in CD44/122(high) memory T cells. Altogether, our results identify a new memory CD8 T cell subset that is generated under sterile inflammatory conditions and involved in the recall contact hypersensitivity reactions that are responsible for allergic contact dermatitis.

Psychological Stress Exerts an Adjuvant Effect on Skin Dendritic Cell Functions In Vivo

Psychological stress affects the pathophysiology of infectious, inflammatory, and autoimmune diseases. However, the mechanisms by which stress could modulate immune responses in vivo are poorly understood. In this study, we report that application of a psychological stress before immunization exerts an adjuvant effect on dendritic cell (DC), resulting in increased primary and memory Ag-specific T cell immune responses. Acute stress dramatically enhanced the skin delayed-type hypersensitivity reaction to haptens, which is mediated by CD8(+) CTLs. This effect was due to increased migration of skin DCs, resulting in augmented CD8(+) T cell priming in draining lymph nodes and enhanced recruitment of CD8(+) T cell effectors in the skin upon challenge. This adjuvant effect of stress was mediated by norepinephrine (NE), but not corticosteroids, as demonstrated by normalization of the skin delayed-type hypersensitivity reaction and DC migratory properties following selective depletion of NE. These results suggest that release of NE by sympathetic nerve termini during a psychological stress exerts an adjuvant effect on DC by promoting enhanced migration to lymph nodes, resulting in increased Ag-specific T cell responses. Our findings may open new ways in the treatment of inflammatory diseases, e.g., psoriasis, allergic contact dermatitis, and atopic dermatitis.

Antigen-presenting cells in allergy

The complex interaction of the innate and adaptive immune system requires flexibility and cooperation among various cell types. In this regard, antigen-presenting-cells (APCs) play a pivotal role in transferring information from the periphery of the organism to lymphoid organs, where they initiate the activation of naive T cells. Dendritic cells, Langerhans' cells (LCs), and macrophages are also critical in the induction of allergic inflammation by presenting allergens to T lymphocytes and by contributing to the local recruitment of effector cells. Because of a complex genetic background, atopic individuals exhibit a dysregulation of T cell-mediated immune mechanisms. Attempts to understand the role APCs play in these pathophysiologic conditions are in progress and may allow development of new treatment strategies. In this review we will focus on the biology of APCs and their unique role in the induction and control of allergic inflammation.

The effect of VAS972 on allergic contact hypersensitivity

BACKGROUND

Contact hypersensitivity (CHS) is a Th1-mediated immune response that can be down-regulated by immunosuppressive agents such as cyclosporine and environmental stimuli such as ultraviolet light. Recently, an immunomodulation therapy, VAS972, has been developed which is believed to down-regulate the Th1 arm of the immune response. This VAS972 involves modifying autologous blood by controlled exposure to the oxidizing agent ozone and UVC light, at an elevated temperature ex vivo. The processed blood is then administered by intramuscular injection.

OBJECTIVE

To further evaluate the immune modulating effect of VAS972.

METHODS

We examined the effect of VAS972 treatment on CHS. Contact hypersensitivity was induced with dinitrofluorobenzene (DNFB) in animals receiving VAS972- processed blood, control blood, or saline. A preliminary study was also conducted to evaluate the effect of plasma and cellular fractions of processed blood.

RESULTS

Mice injected with VAS972-processed blood demonstrated a significantly lower (46%) CHS response than controls. Histologic examination of challenged ear skin from control mice displayed edema with a significant lymphocytic infiltration, whereas animals administered processed blood demonstrated a reduction in lymphocytic infiltration. Mice injected with either plasma or the cellular fraction of the VAS972-treated blood also demonstrated a significant suppression (49% and 41%, respectively).

CONCLUSION

The results of this study demonstrated that VAS972 suppresses CHS and cellular infiltration. Furthermore, the plasma and cellular components of the VAS972 treatment were also able to induce immunosuppression. This further supports the hypothesis that VAS972 down-regulates the Th1 arm of the immune response.

Dendritic cells: role in skin diseases and therapeutic applications

Dendritic cells have entered the centre stage of applied immunological research. Dermatologists knew for quite some time about the extraordinary capacity of these cells to induce immune responses. Recent progress in using these cells as potent adjuvant for the treatment of human cancer has inaugurated an unprecedented wave of publications about the role of these cells for the pathogenesis and treatment of various types of cancers and infectious diseases. This short review attempts to follow some of the origins of dendritic cell research with special regard to dermatology and gives a perspective on newer developments such as the use of dendritic cells to induce antigen-specific tolerance.