Solar urticaria involves rapid mast cell STAT3 activation and neutrophil recruitment, with FcεRI as an upstream regulator.

BACKGROUND: Solar urticaria is a rare photodermatosis characterized by rapid-onset sunlight-induced urticaria, but its pathophysiology is not well understood. OBJECTIVE: We sought to define cutaneous cellular and molecular events in the evolution of solar urticaria following its initiation by solar-simulated UV radiation (SSR) and compare with healthy controls (HC). METHODS: Cutaneous biopsy specimens were taken from unexposed skin and skin exposed to a single low (physiologic) dose of SSR at 30 minutes, 3 hours, and 24 hours after exposure in 6 patients with solar urticaria and 6 HC. Biopsy specimens were assessed by immunohistochemistry and bulk RNA-sequencing analysis. RESULTS: In solar urticaria specimens, there was enrichment of several innate immune pathways, with striking early involvement of neutrophils, which was not observed in HC. Multiple proinflammatory cytokine and chemokine genes were upregulated (including IL20, IL6, and CXCL8) or identified as upstream regulators (including TNF, IL-1ß, and IFN-γ). IgE and FcεRI were identified as upstream regulators, and phosphorylated signal transducer and activator of transcription 3 expression in mast cells was increased in solar urticaria at 30 minutes and 3 hours after SSR exposure, suggesting a mechanism of mast cell activation. Clinical resolution of solar urticaria by 24 hours mirrored resolution of inflammatory gene signature profiles. Comparison with available datasets of chronic spontaneous urticaria showed transcriptomic similarities relating to immune activation, but several transcripts were identified solely in solar urticaria, including CXCL8 and CSF2/3. CONCLUSIONS: Solar urticaria is characterized by rapid signal transducer and activator of transcription 3 activation in mast cells and involvement of multiple chemotactic and innate inflammatory pathways, with FcεRI engagement indicated as an early event.

Impaired expression of metallothioneins contributes to allergen-induced inflammation in patients with atopic dermatitis.

Regulation of cutaneous immunity is severely compromised in inflammatory skin disease. To investigate the molecular crosstalk underpinning tolerance versus inflammation in atopic dermatitis, we utilise a human in vivo allergen challenge study, exposing atopic dermatitis patients to house dust mite. Here we analyse transcriptional programmes at the population and single cell levels in parallel with immunophenotyping of cutaneous immunocytes revealed a distinct dichotomy in atopic dermatitis patient responsiveness to house dust mite challenge. Our study shows that reactivity to house dust mite was associated with high basal levels of TNF-expressing cutaneous Th17 T cells, and documents the presence of hub structures where Langerhans cells and T cells co-localised. Mechanistically, we identify expression of metallothioneins and transcriptional programmes encoding antioxidant defences across all skin cell types, that appear to protect against allergen-induced inflammation. Furthermore, single nucleotide polymorphisms in the MTIX gene are associated with patients who did not react to house dust mite, opening up possibilities for therapeutic interventions modulating metallothionein expression in atopic dermatitis.

Analysis of Immune Landscape in Pancreatic and Ileal Neuroendocrine Tumours Demonstrates an Immune Cold Tumour Microenvironment.

INTRODUCTION: Neuroendocrine tumours (NETs) are rare tumours with an increasing incidence. While low- and intermediate-grade pancreatic NET (PanNET) and small intestinal NET (siNET) are slow growing, they have a relatively high rate of metastasizing to the liver, leading to substantially worse outcomes. In many solid tumours, the outcome is determined by the quality of the antitumour immune response. However, the quality and significance of antitumour responses in NETs are incompletely understood. This study provides clinico-pathological analyses of the tumour immune microenvironment in PanNET and siNETs. METHODS: Formalin-fixed paraffin-embedded tissue from consecutive resected PanNETs (61) and siNETs (131) was used to construct tissue microarrays (TMAs); 1-mm cores were taken from the tumour centre, stroma, tumour edge, and adjacent healthy tissue. TMAs were stained with antibodies against CD8, CD4, CD68, FoxP3, CD20, and NCR1. T-cell counts were compared with counts from lung cancers. RESULTS: For PanNET, median counts were CD8+ 35.4 cells/mm2, CD4+ 7.6 cells/mm2, and CD68+ macrophages 117.7 cells/mm2. For siNET, there were CD8+ 39.2 cells/mm2, CD4+ 24.1 cells/mm2, and CD68+ 139.2 cells/mm2. The CD8+ cell density in the tumour and liver metastases were significantly lower than in the adjacent normal tissues, without evidence of a cell-rich area at the tumour edge that might have suggested immune exclusion. T-cell counts in lung cancer were significantly higher than those in PanNET and siNETs: CD8+ 541 cells/mm2 and CD4+ 861 cells/mm2 (p ≤ 0.0001). CONCLUSION: PanNETs and siNETs are immune cold with no evidence of T cell exclusion; the low density of immune infiltrates indicates poor antitumour immune responses.

Intratumoral follicular regulatory T cells curtail anti-PD-1 treatment efficacy.

Immune-checkpoint blockade (ICB) has shown remarkable clinical success in boosting antitumor immunity. However, the breadth of its cellular targets and specific mode of action remain elusive. We find that tumor-infiltrating follicular regulatory T (TFR) cells are prevalent in tumor tissues of several cancer types. They are primarily located within tertiary lymphoid structures and exhibit superior suppressive capacity and in vivo persistence as compared with regulatory T cells, with which they share a clonal and developmental relationship. In syngeneic tumor models, anti-PD-1 treatment increases the number of tumor-infiltrating TFR cells. Both TFR cell deficiency and the depletion of TFR cells with anti-CTLA-4 before anti-PD-1 treatment improve tumor control in mice. Notably, in a cohort of 271 patients with melanoma, treatment with anti-CTLA-4 followed by anti-PD-1 at progression was associated with better a survival outcome than monotherapy with anti-PD-1 or anti-CTLA-4, anti-PD-1 followed by anti-CTLA-4 at progression or concomitant combination therapy.

Beta-lactam-induced immediate hypersensitivity reactions: A genome-wide association study of a deeply phenotyped cohort.

BACKGROUND: ß-lactam antibiotics are associated with a variety of immune-mediated or hypersensitivity reactions, including immediate (type I) reactions mediated by antigen-specific IgE. OBJECTIVE: We sought to identify genetic predisposing factors for immediate reactions to ß-lactam antibiotics. METHODS: Patients with a clinical history of immediate hypersensitivity reactions to either penicillins or cephalosporins, which were immunologically confirmed, were recruited from allergy clinics. A genome-wide association study was conducted on 662 patients (the discovery cohort) with a diagnosis of immediate hypersensitivity and the main finding was replicated in a cohort of 98 Spanish cases, recruited using the same diagnostic criteria as the discovery cohort. RESULTS: Genome-wide association study identified rs71542416 within the Class II HLA region as the top hit (P = 2 × 10-14); this was in linkage disequilibrium with HLA-DRB1∗10:01 (odds ratio, 2.93; P = 5.4 × 10-7) and HLA-DQA1∗01:05 (odds ratio, 2.93, P = 5.4 × 10-7). Haplotype analysis identified that HLA-DRB1∗10:01 was a risk factor even without the HLA-DQA1∗01:05 allele. The association with HLA-DRB1∗10:01 was replicated in another cohort, with the meta-analysis of the discovery and replication cohorts showing that HLA-DRB1∗10:01 increased the risk of immediate hypersensitivity at a genome-wide level (odds ratio, 2.96; P = 4.1 × 10-9). No association with HLA-DRB1∗10:01 was identified in 268 patients with delayed hypersensitivity reactions to ß-lactams. CONCLUSIONS: HLA-DRB1∗10:01 predisposed to immediate hypersensitivity reactions to penicillins. Further work to identify other predisposing HLA and non-HLA loci is required.

M1hot tumor-associated macrophages boost tissue-resident memory T cells infiltration and survival in human lung cancer.

BACKGROUND: The role of tumor-associated macrophages (TAMs) in determining the outcome between the antitumor effects of the adaptive immune system and the tumor's anti-immunity stratagems, is controversial. Macrophages modulate their activities and phenotypes by integration of signals in the tumor microenvironment. Depending on how macrophages are activated, they may adopt so-called M1-like, antitumor or M2-like, protumor profiles. In many solid tumors, a dominance of M2-like macrophages is associated with poor outcomes but in some tumor types, strong M1-like profiles are linked to better outcomes. We aimed to investigate the interrelationship of these TAM populations to establish how they modulate the efficacy of the adaptive immune system in early lung cancer. METHODS: Macrophages from matched lung (non-tumor-associated macrophages (NTAMs)) and tumor samples (TAMs) from resected lung cancers were assessed by bulk and single-cell transcriptomic analysis. Protein expression of genes characteristic of M1-like (chemokine (C-X-C motif) ligand 9) or M2-like (matrix metallopeptidase 12) functions was confirmed by confocal microscopy. Immunohistochemistry related the distribution of TAM transcriptomic signatures to density of CD8+ tissue-resident memory T cells (TRM) in tumors and survival data from an independent cohort of 393 patients with lung cancer. RESULTS: TAMs have significantly different transcriptomic profiles from NTAMs with >1000 differentially expressed genes. TAMs displayed a strong M2-like signature with no significant variation between patients. However, single-cell RNA-sequencing supported by immuno-stained cells revealed that additionally, in 25% of patients the M2-like TAMs also co-expressed a strong/hot M1-like signature (M1hot). Importantly, there was a strong association between the density of M1hot TAMs and TRM cells in tumors that was in turn linked to better survival. Our data suggest a mechanism by which M1hot TAMs may recruit TRM cells via CXCL9 expression and sustain them by making available more of the essential fatty acids on which TRM depend. CONCLUSIONS: We showed that in early lung cancer, expression of M1-like and M2-like gene signatures are not mutually exclusive since the same TAMs can simultaneously display both gene-expression profiles. The presence of M1hot TAMs was associated with a strong TRM tumor-infiltrate and better outcomes. Thus, therapeutic approaches to re-program TAMs to an M1hot phenotype are likely to augment the adaptive antitumor responses.

Genomic programming of IRF4-expressing human Langerhans cells.

Langerhans cells (LC) can prime tolerogenic as well as immunogenic responses in skin, but the genomic states and transcription factors (TF) regulating these context-specific responses are unclear. Bulk and single-cell transcriptional profiling demonstrates that human migratory LCs are robustly programmed for MHC-I and MHC-II antigen presentation. Chromatin analysis reveals enrichment of ETS-IRF and AP1-IRF composite regulatory elements in antigen-presentation genes, coinciding with expression of the TFs, PU.1, IRF4 and BATF3 but not IRF8. Migration of LCs from the epidermis is accompanied by upregulation of IRF4, antigen processing components and co-stimulatory molecules. TNF stimulation augments LC cross-presentation while attenuating IRF4 expression. CRISPR-mediated editing reveals IRF4 to positively regulate the LC activation programme, but repress NF2EL2 and NF-kB pathway genes that promote responsiveness to oxidative stress and inflammatory cytokines. Thus, IRF4-dependent genomic programming of human migratory LCs appears to enable LC maturation while attenuating excessive inflammatory and immunogenic responses in the epidermis.

Correlation of HPV16 Gene Status and Gene Expression With Antibody Seropositivity and TIL Status in OPSCC.

INTRODUCTION: Human papillomavirus 16 (HPV16) is the main cause of oropharyngeal squamous cell carcinoma (OPSCC). To date, the links between HPV16 gene expression and adaptive immune responses have not been investigated. We evaluated the correlation of HPV16 DNA, RNA transcripts and features of adaptive immune response by evaluating antibody isotypes against E2, E7 antigens and density of tumor-infiltrating lymphocytes (TIL). MATERIAL AND METHODS: FFPE-tissue from 27/77 p16-positive OPSCC patients was available. DNA and RNA were extracted and quantified using qPCR for all HPV16 genes. The TIL status was assessed. Immune responses against E2 and E7 were quantified by ELISA (IgG, IgA, and IgM; 77 serum samples pre-treatment, 36 matched post-treatment). RESULTS: Amounts of HPV16 genes were highly correlated at DNA and RNA levels. RNA co-expression of all genes was detected in 37% (7/19). E7 qPCR results were correlated with higher anti-E7 antibody (IgG, IgA) level in the blood. Patients with high anti-E2 IgG antibody (>median) had better overall survival (p=0.0311); anti-E2 and anti-E7 IgA levels had no detectable effect. During the first 6 months after treatment, IgA but not IgG increased significantly, and >6 months both antibody classes declined over time. Patients with immune cell-rich tumors had higher levels of circulating antibodies against HPV antigens. CONCLUSION: We describe an HPV16 qPCR assay to quantify genomic and transcriptomic expression and correlate this with serum antibody levels against HPV16 oncoproteins. Understanding DNA/RNA expression, relationship to the antibody response in patients regarding treatment and outcome offers an attractive tool to improve patient care.

Single-cell transcriptomic analysis of tissue-resident memory T cells in human lung cancer.

High numbers of tissue-resident memory T (TRM) cells are associated with better clinical outcomes in cancer patients. However, the molecular characteristics that drive their efficient immune response to tumors are poorly understood. Here, single-cell and bulk transcriptomic analysis of TRM and non-TRM cells present in tumor and normal lung tissue from patients with lung cancer revealed that PD-1-expressing TRM cells in tumors were clonally expanded and enriched for transcripts linked to cell proliferation and cytotoxicity when compared with PD-1-expressing non-TRM cells. This feature was more prominent in the TRM cell subset coexpressing PD-1 and TIM-3, and it was validated by functional assays ex vivo and also reflected in their chromatin accessibility profile. This PD-1+TIM-3+ TRM cell subset was enriched in responders to PD-1 inhibitors and in tumors with a greater magnitude of CTL responses. These data highlight that not all CTLs expressing PD-1 are dysfunctional; on the contrary, TRM cells with PD-1 expression were enriched for features suggestive of superior functionality.

Anti-inflammatory potency testing of topical corticosteroids and calcineurin inhibitors in human volunteers sensitized to diphenylcyclopropenone.

AIMS: To quantify the anti-inflammatory potency of topical corticosteroids and topical calcineurin inhibitors by measuring the contact allergic response to a diphenylcyclopropenone (DPCP) challenge in de novo sensitized human volunteers. METHODS: Two randomized, double-blind, vehicle-controlled studies were performed encompassing 76 volunteers: 29 in the first and 47 in the second study. Topical drugs were applied pre- and/or post-treatment in block designs. The compounds were tested simultaneously under occluded patch tests covering DPCP-induced dermatitis. Inhibitory responses were assessed by visual scoring and measurements of the oedema thickness with ultrasound. RESULTS: When applied both before and after the DPCP challenge, significant anti-inflammatory effects were seen in descending order for tacrolimus 0.1% ointment, clobetasol propionate ointment, betamethasone valerate ointment and hydrocortisone butyrate ointment, while pimecrolimus cream, hydrocortisone ointment and vehicles had no significant effect. Only tacrolimus ointment (P < 0.01) demonstrated a consistent significant pre-treatment inhibitory effect compared with an untreated DPCP control. CONCLUSIONS: This human testing method in which the inflammation of experimentally induced allergic patch test reactions is quantified by objective measurement allows an analysis of the anti-inflammatory potency of not only topical corticosteroids, but also of drugs that have no effect on vasoconstriction. The method allowed comparison of the potencies of four topical corticosteroids and two calcineurin inhibitors.

Tissue-resident memory features are linked to the magnitude of cytotoxic T cell responses in human lung cancer.

Therapies that boost the anti-tumor responses of cytotoxic T lymphocytes (CTLs) have shown promise; however, clinical responses to the immunotherapeutic agents currently available vary considerably, and the molecular basis of this is unclear. We performed transcriptomic profiling of tumor-infiltrating CTLs from treatment-naive patients with lung cancer to define the molecular features associated with the robustness of anti-tumor immune responses. We observed considerable heterogeneity in the expression of molecules associated with activation of the T cell antigen receptor (TCR) and of immunological-checkpoint molecules such as 4-1BB, PD-1 and TIM-3. Tumors with a high density of CTLs showed enrichment for transcripts linked to tissue-resident memory cells (TRM cells), such as CD103, and CTLs from CD103hi tumors displayed features of enhanced cytotoxicity. A greater density of TRM cells in tumors was predictive of a better survival outcome in lung cancer, and this effect was independent of that conferred by CTL density. Here we define the 'molecular fingerprint' of tumor-infiltrating CTLs and identify potentially new targets for immunotherapy.

The gene expression and immunohistochemical time-course of diphenylcyclopropenone-induced contact allergy in healthy humans following repeated epicutaneous challenges.

The gene expression time-course of repeated challenge of contact allergy (CA) remains largely unknown. Therefore, using diphenylcyclopropenone (DPCP) as model allergen in healthy humans we set out to examine: (i) the monotonous and complex gene expression time-course trajectories following repeated DPCP challenges to find the predominant gene expression pattern, (ii) the time-course of cell infiltration following repeated DPCP challenges and (iii) the transcriptome of a repeated CA exposure model. We obtained punch biopsies from control and DPCP-exposed skin from ten DPCP sensitized individuals at 5-6 monthly elicitation challenges. Biopsies were used for microarray gene expression profiling, histopathology and immunohistochemical staining. Validation of microarray data by qRT-PCR was performed on 15 selected genes. Early gene expression time points were also validated in an independent data set. An increasing and decreasing trend in gene expression followed by a plateau was predominantly observed during repeated DPCP challenges. Immune responses reached a plateau after two challenges histopathologically, immunohistochemically and in the time-course gene expression analysis. Transcriptional responses over time revealed a Th1/Th17 polarization as three upstream regulators (IFN-γ, IL-1 and IL-17) activated most of the top upregulated genes. Of the latter genes, 9 of 10 were the same throughout the time course. Excellent correlations between array and PCR data were observed. The transcriptional responses to DPCP over time followed a monotonous pattern. This response pattern confirms and supports the newly reported clinical time-course observations in de novo-sensitized individuals showing a plateau response, and thus, there is concordance between clinical response, histopathology, immunohistochemistry and microarray gene expression in volunteers de novo-sensitized to DPCP.

Persistent kallikrein 5 activation induces atopic dermatitis-like skin architecture independent of PAR2 activity.

BACKGROUND: Upregulation of kallikreins (KLKs) including KLK5 has been reported in atopic dermatitis (AD). KLK5 has biological functions that include degrading desmosomal proteins and inducing proinflammatory cytokine secretion through protease-activated receptor 2 (PAR2). However, due to the complex interactions between various cells in AD inflamed skin, it is difficult to dissect the precise and multiple roles of upregulated KLK5 in AD skin. OBJECTIVE: We investigated the effect of upregulated KLK5 on the expression of epidermal-related proteins and cytokines in keratinocytes and on skin architecture. METHODS: Lesional and nonlesional AD skin biopsies were collected for analysis of morphology and protein expression. The relationship between KLK5 and barrier-related molecules was investigated using an ex vivo dermatitis skin model with transient KLK5 expression and a cell model with persistent KLK5 expression. The influence of upregulated KLK5 on epidermal morphology was investigated using an in vivo skin graft model. RESULTS: Upregulation of KLK5 and abnormal expression of desmoglein 1 (DSG1) and filaggrin, but not PAR2 were identified in AD skin. PAR2 was increased in response to transient upregulation of KLK5, whereas persistently upregulated KLK5 did not show this effect. Persistently upregulated KLK5 degraded DSG1 and stimulated secretion of IL-8, IL-10, and thymic stromal lymphopoietin independent of PAR2 activity. With control of higher KLK5 activity by the inhibitor sunflower trypsin inhibitor G, restoration of DSG1 expression and a reduction in AD-related cytokine IL-8, thymic stromal lymphopoietin, and IL-10 secretion were observed. Furthermore, persistently elevated KLK5 could induce AD-like skin architecture in an in vivo skin graft model. CONCLUSIONS: Persistently upregulated KLK5 resulted in AD-like skin architecture and secretion of AD-related cytokines from keratinocytes in a PAR2 independent manner. Inhibition of KLK5-mediated effects may offer potential as a therapeutic approach in AD.

Effect of oral eicosapentaenoic acid on epidermal Langerhans cell numbers and PGD2 production in UVR-exposed human skin: a randomised controlled study.

Langerhans cells (LCs) are sentinels of skin's immune system, their loss from epidermis contributing to UVR suppression of cell-mediated immunity (CMI). Omega-3 polyunsaturated fatty acids show potential to reduce UVR suppression of CMI in mice and humans, potentially through modulation of LC migration. Our objectives were to examine whether eicosapentaenoic acid (EPA) ingestion influences UV-mediated effects on epidermal LC numbers and levels of immunomodulatory mediators including prostaglandin (PG)D2 , which is expressed by LC. In a double-blind randomised controlled study, healthy individuals took 5-g EPA-rich (n=40) or control (n=33) lipid for 12 weeks; UVR-exposed and unexposed skin samples were taken pre- and postsupplementation. Epidermal LC numbers were assessed by immunofluorescence for CD1a, and skin blister fluid PG and cytokines were quantified by LC-MS/MS and Luminex assay, respectively. Presupplementation, UVR reduced mean (SEM) LC number/mm2 from 913 (28) to 322 (40) (P<.001), and mean PGD2 level by 37% from 8.1 (11.6) to 5.1 (5.6) pg/µL; P<.001), while IL-8 level increased (P<.001). Despite confirmation of EPA bioavailability in red blood cells and skin in the active group, no between-group effect of EPA was found on UVR modulation of LC numbers, PGD2 or cytokine levels postsupplementation. Thus, no evidence was found for EPA reduction of photoimmunosuppression through an impact on epidermal LC numbers. Intriguingly, UVR exposure substantially reduced cutaneous PGD2 levels in humans, starkly contrasting with reported effects of UVR on other skin PG. Lowered PGD2 levels could reflect LC loss from the epidermis and/or altered dendritic cell activity and may be relevant for phototherapy of skin disease.

Anti-hapten antibodies in response to skin sensitization.

Whereas T lymphocyte (T cell) activation is the key event in the acquisition of skin sensitization and subsequent elicitation of allergic contact dermatitis, the humoral component of immune responses to organic contact allergens has received little consideration. There is evidence that, in experimental animals, topical exposure to potent contact allergens is associated with B cell activation and proliferation, and hapten-specific antibody production. However, there is very limited evidence available for anti-hapten antibody responses being induced following topical exposure of humans to contact allergens. Nevertheless, it is important to appreciate that there are almost no negative studies in which evidence for antibody production as the result of skin sensitization has been sought and not found. That is, there is absence of evidence rather than evidence of absence. Furthermore, exposure to chemical respiratory allergens, in which the skin has been implicated as a potential route of sensitization, results in anti-hapten antibody responses. It is proposed that skin sensitization to contact allergens will normally be accompanied by antibody production. The phenomenon is worthy of investigation, as anti-hapten antibodies could potentially influence and/or regulate the induction of skin sensitization. Moreover, such antibodies may provide an informative correlate of the extent to which sensitization has been acquired.

Genetic factors in susceptibility to contact sensitivity.

There are clear differences in individual susceptibility to the development of contact allergies; some individuals readily become allergic to many chemicals, and others remain clinically tolerant of everything that they come into contact with. A great number of molecules and pathways can contribute to the perturbation by xenobiotics and the subsequent possible immune response. It is necessary to consider susceptibility in two ways: as allergen-specific and as non-allergen-specific. It is likely that different receptor pathways and processes will be involved in the different forms of susceptibility. As investigations of the genetic control of such susceptibility have failed to identify major genetic control, it is likely that small contributions will be made by many components. Whereas genome-wide associations and transcriptome analyses may reveal genetic clues in the future, explanation of how/why the expression of multiple molecular components can be controlled in a coordinated fashion may follow from investigation of microRNAs. It is becoming clear that microRNAs can regulate the expression of multiple genes and even multiple components of biochemical pathways.

Exercise Intensity and Duration Effects on In Vivo Immunity.

PURPOSE: To examine the effects of intensity and duration of exercise stress on induction of in vivo immunity in humans using experimental contact hypersensitivity (CHS) with the novel antigen diphenylcyclopropenone (DPCP). METHODS: Sixty-four healthy males completed either 30 min running at 60% V˙O2peak (30MI), 30 min running at 80% V˙O2peak (30HI), 120 min running at 60% V˙O2peak (120MI), or seated rest (CON). Twenty min later, the subjects received a sensitizing dose of DPCP; and 4 wk later, the strength of immune reactivity was quantified by measuring the cutaneous responses to a low dose-series challenge with DPCP on the upper inner arm. Circulating epinephrine, norepinephrine and cortisol were measured before, after, and 1 h after exercise or CON. Next, to understand better whether the decrease in CHS response on 120MI was due to local inflammatory or T-cell-mediated processes, in a crossover design, 11 healthy males performed 120MI and CON, and cutaneous responses to a dose series of the irritant, croton oil (CO), were assessed on the upper inner arm. RESULTS: Immune induction by DPCP was impaired by 120MI (skinfold thickness -67% vs CON; P < 0.05). However, immune induction was unaffected by 30MI and 30HI despite elevated circulating catecholamines (30HI vs pre: P < 0.01) and greater circulating cortisol post 30HI (vs CON; P < 0.01). There was no effect of 120MI on skin irritant responses to CO. CONCLUSIONS: Prolonged moderate-intensity exercise, but not short-lasting high- or short-lasting moderate-intensity exercise, decreases the induction of in vivo immunity. No effect of prolonged moderate-intensity exercise on the skin's response to irritant challenge points toward a suppression of cell-mediated immunity in the observed decrease in CHS. Diphenylcyclopropenone provides an attractive tool to assess the effect of exercise on in vivo immunity.

Contact hypersensitivity: quantitative aspects, susceptibility and risk factors.

The development of allergic sensitisation by environmental chemicals results in allergic contact dermatitis and highly undesirable morbidity and disability. This form of hypersensitivity is mediated by specific T lymphocytes that recognise the chemical sensitiser bound to self-proteins. Use of deliberate experimental contact sensitisation with dinitrochlorobenzene (DNCB) has been used to investigate the human immune system which exhibits dose-related responses. Many factors contribute to whether sensitisation occurs and the nature and magnitude of the immune response. Chemicals vary in sensitising potency, mainly reflecting their intrinsic protein-binding properties. The amount of sensitiser reaching the immune system is determined by many factors of which the concentration (dose per unit area), the relative lipid solubility and molecular weight are the most critical. Host-related factors contributing to the nature and magnitude of immune responses are mainly genetically determined including gender, age, the biochemical/physical integrity of the epidermal barrier and the quality of the innate and adaptive immune systems. The underlying mechanisms must be elucidated before it will be possible to make reliable predictions of whether a given individual will develop allergic sensitisation by a given chemical.

Nutritional abrogation of photoimmunosuppression: in vivo investigations.

Skin cancer is a major public health concern, and the primary aetiological factor in the majority of skin cancers is ultraviolet radiation (UVR) exposure. UVR not only induces potentially mutagenic DNA damage but also suppresses cell-mediated immunity (CMI), allowing cancerous cells to escape destruction and progress to tumours. A considerable proportion of an individual's annual sun exposure is obtained outside the vacation period when topical and physical measures for photoprotection are irregularly used. Certain nutrients could provide an adjunctive protective role, and evidence is accruing from experimental studies to support their use in abrogation of photoimmunosuppression. Moreover, developments in clinical research methods to evaluate impact of solar-simulated radiation on cutaneous CMI allow the immune protective potential of nutritional agents to be examined in humans in vivo. This article summarises the mediation of CMI and its suppression by UVR, evaluates the methodology for quantitative assessment in vivo, reviews the human studies reported on nutritional abrogation of photoimmunosuppression including recent randomized controlled trials and discusses the mechanisms of photoprotection by the nutrients. This includes, in addition to antioxidants, novel studies of omega-3 polyunsaturated fatty acids and nicotinamide.