Characterization of the altered cutaneous reactivity of transgenic mice whose keratinocytes overexpress B7-1

Immune receptors CD40 and CD86 in oral keratinocytes and implications for oral lichen planus

Lichen planus (LP) is a chronic T-cell-mediated mucocutaneous inflammatory disease that targets stratified epithelia, including those lining the oral cavity. The intraoral variant of LP (OLP) is associated with interferon (IFN)-γ production by infiltrating T lymphocytes; however, the role of epithelial cells in the etiopathogenesis OLP is not completely understood. There is however a growing body of evidence regarding the involvement of epithelial-derived cytokines, immune receptors, and costimulatory molecules in the pathobiological processes that promote and sustain OLP. In the present study, we used a reverse transcriptase-polymerase chain reaction assay to assess whether CD40-a receptor found mainly on antigen presenting cells-and the costimulatory molecule CD86 were expressed in oral keratinocytes (three strains of primary normal oral keratinocytes and the H357 cell line) in the presence or absence of IFN-γ. To further characterize the involvement of CD40 in OLP, expression and distribution of receptor and ligand (CD40/CD154) in tissues from OLP were evaluated by immunohistochemistry. The present results are the first to show that both CD40 and CD86 are constitutively expressed at low levels in oral keratinocytes and that their expression was enhanced by IFN-γ stimulation. The intensity of CD40 staining in OLP tissues was strong. Taken together, the results strongly suggest that CD40 and CD86 play a role in the pathophysiology of oral inflammatory diseases such as OLP.

Imunopatologia da dermatite de contato alérgica

A dermatite de contato alérgica é consequência de uma reação imune mediada por células T contra químicos de baixo peso molecular, denominados haptenos. É uma condição frequente que ocorre em todas as raças e faixas etárias e afeta a qualidade de vida de seus portadores. O mecanismo imunológico desta doença vem sendo revisto nas últimas décadas com significativo avanço no seu entendimento. A metabolização e o caminho dos haptenos, bem como a formação e o mecanismo de ação das células responsáveis tanto pela reação quanto pelo seu término, são discutidos neste artigo

Nanotechnology in vaccine development: a step forward

The study of nanotechnology for epicutaneous delivery of pharmaceuticals and vaccines is burgeoning. Topically applied nanomaterials have been shown to enter tape-stripped skin and reach draining lymph nodes in an inbred strain of mice. Nanomaterials in the form of plasmid DNA, proteins, and virus particles accumulate in hair follicles, diffuse via dendritic cells to draining lymph nodes, and elicit antigen-specific humoral and cell-mediated immunity. Topically immunized mice have also demonstrated resistance to infection with live virus. Advantages of nanotechnology include uniformity, reproducibility, and precision in the synthesis and manufacture of candidate compounds. Combined with novel pharmacokinetics and the possibility of targeted therapy, nanotechnology-based vaccines may prove superior to existing vaccines and have the potential to open therapeutic avenues for treating infectious disease and malignancy.

Topical Imiquimod Treatment Prevents UV-Light Induced Loss of Contact Hypersensitivity and Immune Tolerance

Imiquimod (1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4-amine) is a TLR7 agonist that induces cytokine production in TLR7 bearing antigen-presenting cells (APCs), including IL-12, a cytokine that has been demonstrated to be a critical effector molecule for contact hypersensitivity (CHS). To test our hypothesis that topical applications of imiquimod may protect the skin immune system against the deleterious effects of UV light exposures, we treated animals with this agent, or its vehicle or nothing before UV exposures. Although topical imiquimod exposures before UV light did not prevent the depletion of epidermal Langerhans cells, it did prevent the loss of CHS. IL-12 was important in the protective role of imiquimod in preventing UV-induced loss of CHS, as systemic treatment of mice with an anti-IL-12 p70 monoclonal antibody blocked the protective effects of imiquimod. Additionally, only imiquimod-treated mice were resistant to hapten-specific tolerance induction after UV irradiation at the site of the initial sensitization with the hapten 2,4 dinitro-1-fluorobenzene. To model for the effects of TLR7 activation on the UV effect on antigen-APCs, XS52 cell line was used to study this interaction in an in vitro model system. This cell line expressed mRNA for TLR7, downregulated IkappaB, phosphorylated c-Jun N-terminal kinase, and secreted cytokines after exposure to imiquimod or lipopolysaccharide. Activation of the TLR7 signaling pathway on XS52 before UV-light exposures enhanced IL-12p70 secretion by this cell line. Similarly, activation of TLR7 on XS52 before UV-light exposure also prevented the UV-induced loss of IFN-gamma triggering in T cells during an allogeneic mixed lymphocyte reaction. Imiquimod-treated, UV-irradiated XS52 triggered a more vigorous IFN-gamma production than did either imiquimod-treated XS52 or UV-irradiated XS52, again suggesting a synergy between the two treatments. Lastly, enriched lymph node CD11c+ APCs from mice treated with UV irradiation, imiquimod alone or the combination of UV irradiation and imiquimod indicated the same in vivo synergy between imiquimod irradiation and UV irradiation in enhancing IL-12p70 production. These data suggest that topical imiquimod applications may play a role in preventing UV-induced impairment of the skin immune system, which is thought to be one of the critical events that allow the development of UV-induced skin cancers.

Keratinocyte-derived, CD80-mediated costimulation is associated with hapten-specific IgE production during contact hypersensitivity to TH1 haptens

Background B7-1 transgenic mice exhibit exaggerated and persistent contact hypersensitivity responses compared with normal mice. Objective Because B7-1 and B7-2 deliver different costimulatory signals to T cells during antigen presentation, the purpose of this study was to compare B7-1 and B7-2 on keratinocytes and to compare their effects on contact hypersensitivity. Methods Contact hypersensitivity was studied in transgenic mice whose keratinocytes constitutively expressed B7-1, B7-2, or no costimulatory molecules (nontransgenic mice). Results B7-1 transgenic mice, and to a lesser extent B7-2 transgenic mice, developed exaggerated ear swelling responses after sensitization and challenge with haptens such as trinitrochlorobenzene or dinitrofluorobenzene. Ear swelling responses in B7-1 transgenic mice were characterized by the presence of markedly elevated inflammatory cytokine transcripts (IL-6, TNF-alpha, and lymphotoxin beta) as well as IL-10 compared with either B7-2 or nontransgenic mice. Hapten-specific IgE was detected by ELISA in B7-1 transgenic mice but not B7-2 transgenic or nontransgenic mice. Only B7-1 transgenic mice exhibited significant immediate type ear swelling responses to the hapten trinitrochlorobenzene. In addition, their sera can passively transfer cutaneous anaphylaxis to naive C57BL/6 mice, indicating that the hapten-specific IgE was relevant to the immediate ear swelling responses. Conclusion These data suggest that keratinocyte-derived costimulation mediated by B7-1 but not B7-2 results in the emergence of T H 2-lymphocyte immune responses to T H 1 haptens. Because human keratinocytes have been noted to express B7-1-like molecules in certain inflammatory skin diseases, this model may be important in understanding the pathophysiology of T H 2-lymphocyte-mediated skin diseases such as atopic dermatitis.

Keratinocytes in atopic dermatitis: inflammatory signals

Atopic dermatitis (AD) is a chronic inflammatory skin disorder that usually predates the development of allergic airway disease. In most cases, this is thought to be an allergen-driven disease with prominent roles played by antigen presenting cells and effector Th2 cells. But keratinocytes, by virtue of their location, provide an important window to the environment and are also thought to contribute to the development of AD. In this review, we discuss several biologic attributes of keratinocytes that are relevant for AD: 1) intrinsic defects in barrier function, 2) production of inflammatory mediators that promote or maintain allergic inflammation, 3) keratinocyte apoptosis, 4) effects of staphylococcal toxins on keratinocytes, and 5) potential consequences of the expression of cosignaling molecules (eg, B7 family members) and receptors important for innate immune responses (eg, Toll receptors). Clearly, these findings have highlighted a more active role played by the epithelium than was previously recognized.

Heterogeneity of CD80 gene transcription by human keratinocytes to allergens and irritants: relevance to allergic contact dermatitisin vivo

Using an in vitro assay for CD80 promoter activity, the transcriptional response of primary cultured human keratinocytes from different donors in response to allergens and irritants was studied. The CD80 promoter activity was increased reproducibly after exposure to certain chemicals. The epithelial cell lines HeLa and HaCaT also increased CD80 transcriptional activity in response to exposure to a panel of different allergens and irritants. Normal or immortalized keratinocytes responded reproducibly with a unique pattern to a panel of chemicals in which the culture increases CD80 transcription after exposure to certain chemicals and has no increase in CD80 transcription after exposure to other chemicals. Some keratinocyte cultures responded positively to certain chemicals whereas others did not respond to the same chemicals. Cultured keratinocytes from 16 of 20 adult donors (80%) responded to nitrochlorobenzene in vitro by increasing CD80 transcriptional activity, thus predicting subsequent sensitization to this same hapten (chi2= 7.2, P <0.0073). Thus, a keratinocyte CD80 gene expression assay exhibits good sensitivity in predicting allergic contact dermatitis for sensitizers such as dinitrochlorobenzene. These data suggest that there is a rationale for developing the use of gene-transcription-based predictive assays to identify individual susceptibility to cutaneous reactivity after exposure to allergens and irritants.

Keratinocytes induce local tolerance to skin graft by activating interleukin-10-secreting T cells in the context of costimulation molecule B7-H1

BACKGROUND

Intermingled skin grafting using autologous skin islets inlaid in allogeneic skin sheets was found to delay graft rejection, contributing to a significant reduction in mortality for patients with severe burns. In this study we examine the down-regulatory mechanisms underlying the effect of the autologous skin islets.

METHODS

Mixed culture of lymphocytes with epidermal cells of autologous and allogeneic origin were performed with a comparing of cell activity from cytokine-knockout mice. And the Th1/Th2-related cytokine profiles were examined.

RESULTS

Autologous keratinocytes act as potent inducers of suppression in the mixed culture by making a shift of the cytokine profile from Th1 to Th2. The observed suppression is predominantly mediated by interleukin (IL)-10, because the effect could be reversed by application of a neutralizing antibody to IL-10. The results of reconstitution experiments in BALB/c mice, with or without IL-10 gene-knockout, are consistent with this finding. These demonstrated that T cells were main effective components for the IL-10-related suppression. Furthermore, a newly identified member of the human B7 family (B7-H1) is found to play an important role in activating human IL-10-secreting lymphocytes. When transfected with the CD80 gene, autologous keratinocytes lost the ability to down-regulate the mixed cell culture, which effect could be reversed by introduction of the anti-CD80 antibody.

CONCLUSIONS

Our study provides new evidence that autologous keratinocytes present in intermingled skin grafts are inducers for local immune tolerance by expression of B1-H1 in their activation of the IL-10-secreting T cells.

Imiquimod 5-percent cream does not alter the natural history of recurrent herpes genitalis: a phase II, randomized, double-blind, placebo-controlled study

Present strategies for control of herpes genitalis recurrences require multiple daily doses of antiviral medication. Imiquimod, an immune response modifier, induces alpha interferon and interleukin-12; application in the presence of local herpes antigens during a recurrence may augment herpes simplex virus (HSV)-specific cell-mediated immunity. To test this theory, we performed a randomized, double-blind, placebo-controlled study of imiquimod 5% cream to assess safety and efficacy for decreasing recurrences. Patients with six or more recurrences of herpes genitalis per year applied study cream (imiquimod or placebo) to lesions one, two, or three times per week for 3 weeks for each recurrence during a 16-week treatment period. This was followed by a 16-week observation period. Of 124 patients randomized to the study, 103 completed the treatment period and 93 completed the observation period. The median times to first genital herpes recurrence were 53 days for those receiving placebo (n = 30) and 54, 60, and 64 days for those receiving imiquimod one time per week (n = 34), two times per week (n = 32), and three times per week (n = 28), respectively. The median annualized recurrence rates during the treatment period were 3.8, 4.9, 3.2, and 3.1, respectively. There were no statistically significant differences in the time to first recurrence or in the annualized recurrence rate between the imiquimod and placebo groups in either the treatment or the observation period. A trend in increased rates of local adverse events at the application site and a delay in lesion healing with more frequent dosing suggested a pharmacologic effect. Although clinical efficacy has been observed for imiquimod in other conditions in which a TH1-type immune response may be beneficial, including other viral infections such as those caused by human papillomavirus, no apparent effect on the short-term natural history of herpes genitalis recurrences was observed.

The keratinocyte as a target for staphylococcal bacterial toxins

Skin infections with Staphylococcus aureus are not only an important cause of morbidity and even mortality, but are thought to serve as initiation and/or persistance factors for numerous inflammatory skin diseases, including psoriasis and atopic dermatitis. One mechanism by which S. aureus can modulate the immune system is through the production of proteins such as superantigenic toxins, Protein A, as well through the cytolytic alpha-toxin. This review serves to discuss the biology of these three types of proteins, with emphasis on their ability to stimulate the production of powerful pro-inflammatory lipid- and protein-derived cytokines in keratinocytes. Characterization of interactions between these proteins and the keratinocyte can provide a better understanding of how bacterial infection modulates inflammatory skin diseases, as well as provide the basis for improved therapies involving antibacterial agents.

Allergens and irritants transcriptionally upregulate CD80 gene expression in human keratinocytes

The human CD80 costimulatory molecule is an important signal between professional antigen-presenting cells and T helper cells. The immunobiology of CD80 expression by keratinocytes, especially during allergic and irritant contact dermatitis, however, is less well understood. CD80 cell surface expression and gene transcription by keratinocytes was increased when keratinocytes were exposed to certain allergens (chemicals that induce inflammation via hapten-specific T cells) and irritants (chemicals that are toxic to epidermal cells). Therefore, the human CD80 promoter was cloned and luciferase reporter constructs containing various promoter fragments were engineered. Promoter mapping of these CD80 constructs in transiently transfected keratinocytes showed that a construct containing the proximal 231 bp immediately upstream of the transcription start site of the CD80 promoter was most active in keratinocytes and was inducible to a level ranging from 2- to 10-fold higher in keratinocytes treated with certain allergens and irritants, compared with untreated keratinocytes. This pattern of promoter fragment activity in keratinocytes is identical to that found in professional antigen-presenting cells. This is the first demonstration that the CD80 promoter is active in keratinocytes and that this activity is further increased in keratinocytes treated with certain allergens and irritants. These data suggest that allergens and irritants may, in part, break peripheral tolerance by their direct effects on keratinocyte costimulatory molecule expression, thereby facilitating interactions with epidermotropic T helper cells via the CD80-CD28 or CTLA-4 pathways.

CD86 (B7-2), but not CD80 (B7-1), expression in the epidermis of transgenic mice enhances the immunogenicity of primary cutaneous Candida albicans infections

Transgenic (Tg) mice whose epidermal keratinocytes constitutively overexpress either B7-1 (CD80) or B7-2 (CD86) exhibited exaggerated cutaneous delayed type hypersensitivity (DTH) to haptens compared to non-Tg mice. To determine whether enhanced DTH in these Tg mice is seen in response to cutaneous fungal infections, a primary infection with Candida albicans was established by inoculating this organism on the occluded skin of Tg and non-Tg mice. These infections resolved 7 days after removal of occlusive dressing in all three groups of mice, without evidence of exaggerated inflammation in either the Tg or non-Tg mice. Only B7-2 Tg mice developed enhanced Th1-lymphocyte-mediated immune responses to C. albicans antigens after resolving this infection: enhanced footpad swelling in response to intradermal C. albicans antigens, enhanced production of mRNA encoding Th1 lymphokines in draining lymph nodes, and increased gamma interferon secreted into culture supernatants by lymph node T lymphocytes stimulated with Candida antigens in vitro. Lastly, Western blotting of sera from mice that had resolved this fungal infection indicated that only B7-2 Tg mice recognized a wide range of Candida-associated antigens. These data suggest that these two costimulatory molecules, when expressed by keratinocytes, do not deliver identical signals to C. albicans antigen-reactive Th1 lymphocytes. The enhanced immune response in B7-2 Tg mice to a cutaneous C. albicans infection demonstrates the importance of antigen presentation and costimulation in immune reactivity to fungi. Furthermore, B7-2 Tg mice may be useful in identification of protective Candida antigens.