The effect of oral indomethacin on psoriasis treated with the Ingram regime

Human fibroblasts support the expansion of IL-17-producing T cells via up-regulation of IL-23 production by dendritic cells

The initiation of immune responses is associated with the maturation of dendritic cells (DCs) and their migration to draining lymph nodes. En route activated DCs encounter cells of the tissue microenvironment, such as fibroblasts. Because we have shown that DCs interact with fibroblasts during immune responses, we studied the impact of skin fibroblasts on human monocyte-derived DC function and subsequent human T-cell (TC) differentiation. We show that fibroblasts support interleukin-23 (IL-23) secretion from DCs preactivated by lipopolysaccharide (DC(act)) compared with lipopolysaccharide-activated DCs alone. The underlying complex feedback-loop mechanism involves IL-1β/tumor necrosis factor-α (from DC(act)), which stimulate fibroblasts prostaglandin E(2) production. Prostaglandin E(2), in turn, acts on DC(act) and increases their IL-23 release. Furthermore, fibroblast-stimulated DC(act) are far superior to DC(act) alone, in promoting the expansion of Th17 cells in a Cox-2-, IL-23-dependent manner. Using CD4(+)CD45RO(+) memory TCs and CD4(+)CD45RA(+) naive TCs, we showed that fibroblasts induce a phenotype of DC(act) that promotes the expansion of Th17 cells. Moreover, in psoriasis, a prototypic immune response in which the importance of IL-23/Th17 is known, high expression of Cox-2 in fibroblasts was observed. In conclusion, skin fibroblasts are involved in regulation of IL-23 production in DCs and, as a result, of Th17 expansion.

Aetiology and pathogenesis of psoriasis

The hereditary transmission of psoriasis is suggested by epidemiological data and familial association, but remains incompletely defined, not appearing to follow simple autosomal dominant or recessive patterns. The confusion may be due to a multifactorial inheritance, or to inheritance of only a 'predisposition' to disease which requires an environmental stimuli for expression. Recent advances in genetic mapping indicate genetic heterogeneity, and suggest that definition of psoriasis at the level of the gene may soon be possible. Two of the three major pathogenic features of psoriasis--abnormal keratinocyte differentiation and hyperproliferation of keratinocytes--are secondary to altered growth and maturation kinetics related to the normal wound healing process. The third major pathogenic feature--infiltration of inflammatory components into the skin--can be explained by keratinocyte release of a wide variety of cytokines, immune and inflammatory modulators. Three theories have been proposed for the relationship between epidermal keratinocyte and immunocyte activation. The first theory proposes direct activation of epidermal keratinocytes by physical, chemical, or ultraviolet injury, increasing the synthesis and release of cytokines, which trigger T-lymphocyte activation in an antigen-independent fashion. The other two theories propose persistent T-lymphocyte stimulation as a result of either antigen/superantigen presentation by antigen-presenting cells, or as a result of autoreactivity. One or more of these mechanisms may be operative in different patients, at different times, or in response to different environmental stimuli. Also, the genetic heterogeneity of psoriasis suggests that different mechanisms could be linked to different genetic loci. Advances in understanding the aetiology and pathogenesis of psoriasis suggest the possibility of innovative, targeted therapies.