RESUMEN
It is unknown whether closely related epidermal dendritic cells, Langerhans cells (LCs), and dermal dendritic cells (DDCs) have unique functions. In this study, we show that human DDCs have a broad TLR expression profile, whereas human LCs have a selective impaired expression of cell surface TLR2, TLR4, and TLR5, all involved in bacterial recognition. This distinct TLR expression profile is acquired during the TGF-beta1-driven development of LCs in vitro. Consequently, and in contrast to DDCs, LCs weakly respond to bacterial TLR2, TLR4, and TLR5 ligands in terms of cytokine production and maturation, as well as to whole Gram-positive and Gram-negative bacteria, whereas their responsiveness to viral TLR ligands and viruses is fully active and comparable to DDCs. Unresponsiveness of LCs to bacteria may be a mechanism that contributes to tolerance to bacterial commensals that colonize the skin.
Asunto(s)
Epidermis/inmunología , Bacterias Gramnegativas/inmunología , Bacterias Grampositivas/inmunología , Tolerancia Inmunológica , Células de Langerhans/inmunología , Receptor Toll-Like 2/inmunología , Receptor Toll-Like 4/inmunología , Receptor Toll-Like 5/inmunología , Diferenciación Celular/efectos de los fármacos , Diferenciación Celular/inmunología , Células Cultivadas , Células Epidérmicas , Epidermis/metabolismo , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/inmunología , Humanos , Tolerancia Inmunológica/efectos de los fármacos , Células de Langerhans/citología , Células de Langerhans/metabolismo , Receptor Toll-Like 2/biosíntesis , Receptor Toll-Like 4/biosíntesis , Receptor Toll-Like 5/biosíntesis , Factor de Crecimiento Transformador beta1/inmunología , Factor de Crecimiento Transformador beta1/farmacología , Virus/inmunologíaRESUMEN
Keratinocytes contribute to cutaneous immune responses through the expression of cytokines. We investigated whether human keratinocytes can express IL-23, a newly defined IFN-gamma-inducing cytokine composed of a unique p19 subunit and a p40 subunit shared with IL-12. Cultured keratinocytes from normal and lesional psoriatic skin were found to express constitutively mRNA for both subunits of IL-23. Low but significant levels of the heterodimeric IL-23 protein could be detected in cell lysates and supernatants from stimulated keratinocytes by immunoblotting and ELISA. Functional analysis showed that these low levels of keratinocyte-derived IL-23 were sufficient to enhance the IFN-gamma production by memory T cells. Immunostaining of skin sections confirmed expression of both subunits of IL-23 by keratinocytes in situ and also revealed expression of this cytokine in the dermal compartment. IL-23 expression was significantly higher in psoriatic lesional skin, compared with normal and psoriatic nonlesional skin. The immunostained preparations of cultured cells and IL-23 levels in culture supernatants did not show any difference between normal and psoriatic keratinocytes indicating no intrinsic aberration of IL-23 expression in keratinocytes from psoriatic skin. Double staining of cytospin preparations demonstrated that IL-23 p19 is also expressed by epidermal Langerhans cells, dermal dendritic cells, and macrophages. Psoriasis is a chronic inflammatory skin disease mediated by IFN-gamma-expressing type 1 memory T cells. As IL-23 is important to activate memory T cells to produce IFN-gamma, its augmented expression of IL-23 by keratinocytes and cutaneous APC may contribute to the perpetuation of the inflammation process in this disease.
Asunto(s)
Adyuvantes Inmunológicos/biosíntesis , Interleucinas/biosíntesis , Queratinocitos/inmunología , Queratinocitos/metabolismo , Psoriasis/inmunología , Piel/inmunología , Piel/metabolismo , Adyuvantes Inmunológicos/genética , Células Presentadoras de Antígenos/inmunología , Células Presentadoras de Antígenos/metabolismo , Células Presentadoras de Antígenos/patología , Células Cultivadas , Dermis/inmunología , Dermis/metabolismo , Dermis/patología , Dimerización , Epidermis/inmunología , Epidermis/metabolismo , Epidermis/patología , Humanos , Memoria Inmunológica/fisiología , Mediadores de Inflamación/metabolismo , Mediadores de Inflamación/fisiología , Interferón gamma/biosíntesis , Interleucina-23 , Subunidad p19 de la Interleucina-23 , Interleucinas/genética , Queratinocitos/patología , Psoriasis/metabolismo , Psoriasis/patología , ARN Mensajero/metabolismo , Linfocitos T/metabolismoRESUMEN
The type 1 T cell-derived cytokine interferon gamma (IFN-gamma) is overexpressed in psoriatic lesional skin. Recently, we have shown that a single high erythemal dose of broad-band ultraviolet B (UVB) irradiation reduces type 1 and favors type 2, i.e. interleukin-4 (IL-4), cytokine expression in normal and psoriatic skin. In this study, we wanted to see whether conventional narrow-band UVB (NB-UVB) therapy (i.e. repeated exposure to nonerythemal doses) also affects type 1/type 2 cytokine expression of T cells present in chronic plaque type psoriatic lesions. Staining of cryostat sections showed decreased expression of both IFN-gamma and IL-4 in situ after NB-UVB therapy. CD4(+) dermal T cell lines, derived from psoriatic lesional skin, displayed significantly decreased intracellular IFN-gamma expression during and after NB-UVB therapy as compared to pretreatment values. Intracellular IL-4 expression was increased in most patients after therapy. Analysis of the supernatants of these stimulated dermal T cells revealed that IFN-gamma production decreased significantly following NB-UVB therapy, whereas IL-4 expression increased in the T cell supernatants from most patients, confirming the intracellular determinations. In addition, IL-10 and transforming growth factor-beta levels in the supernatants appeared to be increased in the majority of patients following UVB therapy. Apart from the well-known killing effect of UVB on T cells, our results show that the improvement in psoriatic skin following NB-UVB therapy is also due to a reduced capacity of the surviving dermal T cells to express the proinflammatory cytokine IFN-gamma.
Asunto(s)
Interferón gamma/biosíntesis , Psoriasis/radioterapia , Linfocitos T/inmunología , Terapia Ultravioleta , Humanos , Interleucina-4/biosíntesis , Psoriasis/inmunología , Piel/inmunología , Piel/efectos de la radiaciónRESUMEN
To determine the effect of UVB exposure on the balance of type-1 or type-2 T-cells in skin, we examined the expression of key markers interferon (IFN)-gamma and interleukin (IL)-4 in cryostat sections. IFN-gamma mRNA was clearly detectable in nonirradiated control skin, and IFN-gamma protein was found in 2% of the dermal CD3pos T-cells, whereas IL-4 mRNA was hardly detectable, and no IL-4 protein was found. In contrast, IL-4 mRNA expression increased upon irradiation, and IL-4 was found in 2% of the T-cells at day 2 after UVB-exposure. Concomitantly, IFN-gamma mRNA expression decreased, and IFN-gamma protein became absent. We also analyzed T-cells present in primary dermal cell cultures, which were used as an in vitro equivalent of the in vivo situation. As compared with T-cells from control skin, T-cells in dermal cell cultures from UVB-exposed skin displayed an increased IL-4 and decreased IFN-gamma expression. No such skewing occurred when the T-cells from irradiated skin were cloned in the absence of a dermal microenvironment. Except for an occasional positive T-cell, type-1-associated cell-surface markers (CCR5, CXCR3) or type-2 markers (CCR3, CD30, CRTH2) were undetectable in situ. But these markers were expressed on cultured dermal T-cells from UVB-exposed and control skin at a comparable level, but did not correlate with the IFN-gamma and IL-4 production. Altogether, UVB-induced changes of the dermal microenvironment favor the development of type-2 T-cells.
Asunto(s)
Piel/efectos de la radiación , Linfocitos T/efectos de la radiación , Rayos Ultravioleta , Secuencia de Bases , Células Cultivadas , Cartilla de ADN , Humanos , Interferón gamma/genética , Interleucina-4/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Piel/citología , Piel/metabolismo , Linfocitos T/citologíaRESUMEN
UVB irradiation can cause considerable changes in the composition of cells in the skin and in cutaneous cytokine levels. We found that a single exposure of normal human skin to UVB induced an infiltration of numerous IL-4(+) cells. This recruitment was detectable in the papillary dermis already 5 h after irradiation, reaching a peak at 24 h and declining gradually thereafter. The IL-4(+) cells appeared in the epidermis at 24 h postradiation and reached a plateau at days 2 and 3. The number of IL-4(+) cells was markedly decreased in both dermis and epidermis at day 4, and at later time points, the IL-4 expression was absent. The IL-4(+) cells did not coexpress CD3 (T cells), tryptase (mast cells), CD56 (NK cells), and CD36 (macrophages). They did coexpress CD15 and CD11b, showed a clear association with elastase, and had a multilobed nucleus, indicating that UVB-induced infiltrating IL-4(+) cells are neutrophils. Blister fluid from irradiated skin, but not from control skin, contained IL-4 protein as well as increased levels of IL-6, IL-8, and TNF-alpha. In contrast to control cultures derived from nonirradiated skin, a predominant type 2 T cell response was detected in T cells present in primary dermal cell cultures derived from UVB-exposed skin. This type 2 shift was abolished when CD15(+) cells (i.e., neutrophils) were depleted from the dermal cell suspension before culturing, suggesting that neutrophils favor type 2 T cell responses in UVB-exposed skin.