Psychological influences in psoriasis

It has long been recognized that living with a chronic condition, such as psoriasis, can have considerable impact on the individual concerned. In turn there is increased understanding that the psychological distress encountered as a result of this experience can have implications for the course of the disease. This short review takes this as a starting point and reviews psychological influences in psoriasis. The nature of the link between psoriasis and stress is explored and its implications for the patient are discussed in psychological and clinical terms. There seems little doubt that stress, either environmental or psoriasis induced, impacts on our patients and has important implications for the management of psoriasis.

A Short-Term Screening Protocol, Using Fibrillin-1 as a Reporter Molecule, for Photoaging Repair Agents

Photoaged skin is characterized by coarse and fine wrinkles. The mechanisms of wrinkle formation are undetermined, but appear to be due to changes within the matrix of the dermis and at the dermal-epidermal junction. Previous studies have identified marked reductions in procollagens I and III, collagen VII, and the fibrillin-rich microfibrillar apparatus in this area. Topically applied all-trans retinoic acid can repair photoaged dermal matrix, but this takes at least 6 mo of treatment. In this study, we have examined the abundance and distribution of fibrillin-1 prior to, and following, 192 wk of all-trans retinoic acid treatment. We have further developed a short-term protocol to determine the utility of potential repair agents, using fibrillin-1 as the marker for outcome. Individuals with clinically assessed severe photoaging were recruited to the study (n = 8). 0.025% all-trans retinoic acid, 5% sodium lauryl sulfate (irritant control), or vehicle were applied under occlusion to photoaged extensor forearm. A fourth control area was also occluded. After 96 h, punch biopsies were taken under local anesthesia and processed for either transmission electron microscopy or snap frozen. Frozen sections were prepared for immunohistochemistry and in situ hybridization immunohistochemistry. Electron microscopy revealed aberrant elastic fibers in the papillary dermis of photoaged forearm skin, with sparse microfibrillar apparatus and interstitial collagen. After application of 0.025% all-trans retinoic acid, there was increased deposition of both these dermal matrix components, with the aberrant elastic fibers no longer apparent. Significant increases (p < 0.05) were observed at the protein and mRNA levels for fibrillin-1 following all-trans retinoic acid and sodium lauryl sulfate treatments, with all-trans retinoic acid having a significantly greater effect than irritant control (p < 0.001); however, neither application had significant effect on the abundance of collagen VII or its mRNA. Investigation of collagen I synthesis revealed no difference following treatments. To ascertain the clinical relevance of using fibrillin-1 as a marker for photoaging, facial skin was biopsied at baseline and after long-term (192 wk) topical all-trans retinoic acid treatment (n = 5). Biopsies were wax-embedded and sections prepared for immunohistochemistry for fibrillin-1. Significant increases in the abundance of the microfibrillar apparatus was observed proximal to the dermal- epidermal junction (p < 0.001) following long-term all-trans retinoic acid application. This study indicates that all-trans retinoic acid can significantly affect fibrillin-1 content in photoaged skin. Furthermore, fibrillin-1 can be used as a "reporter" molecule in short-term protocols for testing the utility of topical agents in the repair of photoaged skin.

Activation of oral keratinocytes by mercuric chloride: relevance to dental amalgam-induced oral lichenoid reactions

BACKGROUND

Despite the benefits of mercury-containing amalgam dental fillings there are growing concerns regarding the potential adverse health effects arising from exposure to mercury released from fillings. In some individuals this process may result in a local lichenoid reaction of the oral mucosa.

OBJECTIVES

The aim of this study was to investigate the possibility that mercury salts released from amalgam fillings might act directly on oral keratinocytes to induce changes that could promote the development of such lesions.

METHODS

In vitro experiments were performed in which normal oral and cutaneous keratinocytes were cultured in the presence of mercuric chloride (HgCl2). ICAM-1 expression and the release of cytokines was determined by enzyme-linked immunosorbent assay techniques. T-cell binding to HgCl2-pretreated keratinocytes was assessed using a colorimetric method.

RESULTS

Subcytotoxic concentrations of HgCl2 induced a concentration-related increase in ICAM-1 expression and consequent T-cell binding on oral, but not cutaneous, keratinocytes. HgCl2 also stimulated the release of low levels of tumour necrosis factor-alpha and interleukin-8 (but not RANTES), and inhibited the release of interleukin-1alpha by oral keratinocytes.

CONCLUSIONS

This study provides evidence that oral keratinocytes may play an integral part in initiating the pathogenesis of amalgam-induced lichenoid reactions.

Intermittent short courses of cyclosporine microemulsion for the long-term management of psoriasis: a 2-year cohort study

BACKGROUND

Cyclosporine is effective in psoriasis, but long-term continuous therapy may be limited by renal impairment and hypertension. Intermittent short courses of treatment should minimize side effects and improve the risk-benefit ratio.

OBJECTIVE

Our purpose was to assess the long-term efficacy and safety of intermittent short courses of the microemulsion formulation of cyclosporine (Neoral) in the management of chronic plaque psoriasis unresponsive to topical therapies.

METHODS

In a multicenter open cohort study, 76 subjects were treated intermittently over a 2-year period. Patients with chronic plaque psoriasis were treated with cyclosporine until clearance of psoriasis or for a maximum of 12 weeks. Patients were then randomized into two groups. Group A stopped cyclosporine abruptly, whereas group B had the dose reduced by 1 mg/kg per day each week until cessation, which was within 4 weeks. On relapsing, patients received further courses of cyclosporine. Intermittent treatment was continued in this way for 2 years.

RESULTS

There was no statistically significant difference in the percentage of time in remission during the 2-year period between patients randomized to stop cyclosporine abruptly (56.2%) and patients randomized to taper cyclosporine within 4 weeks (61.8%). The mean percentage of time that patients received treatment during the study was 40.5% for randomization group A, 46.2% for randomization group B, and 42.8% overall. The median time to relapse was 115.5 days after the first treatment course but became progressively shorter after multiple treatment courses. Mean blood pressure and serum creatinine levels did not show any clinically significant changes over time.

CONCLUSIONS

This study indicates that intermittent short courses of cyclosporine are effective in patients with moderate to severe psoriasis for up to 2 years while improving the safety profile relative to continuous cyclosporine monotherapy.

Cytokine gene polymorphisms in psoriasis

BACKGROUND

Cytokine production is under genetic control, and certain allelic variants of cytokine genes are associated with higher or lower cytokine production in vitro and in vivo. Psoriasis is associated with an overexpression in the involved skin of T-helper cell type 1 (Th1) cytokines, e.g. interferon (IFN) -gamma and tumour necrosis factor (TNF) alpha and relative underexpression of Th2 cytokines, e.g. interleukin (IL) -4 and IL-10. Objective We investigated the hypothesis that allelic variants of genes for a high production of Th1 cytokines or TNF-alpha, or conversely low production of Th2 cytokines might represent a risk factor for developing psoriasis.

METHODS

Genotyping for IFN-gamma, IL-10, IL-4 and TNF-alpha was undertaken for 84 patients with psoriasis and compared with control data on file.

RESULTS

Genotype frequencies showed no differences between patients and controls for IFN-gamma, TNF-alpha or IL-4. For IL-10, patients with late onset psoriasis (over 40 years) were more likely to be heterozygous at position - 1082 (P = 0.02), corresponding to intermediate production of IL-10 in vitro and in vivo.

CONCLUSIONS

Psoriasis is not determined by a genotype consistent with high production of Th1 cytokines or low production of Th2 cytokines. Thus, the Th1 cytokine profile found in psoriatic plaques is most likely a consequence of local factors.

Psoriasis: the future

The aetiology of psoriasis is still unclear but our knowledge of the psoriatic process has grown substantially over the last two decades. The future will undoubtedly bring advances in our understanding of the pathogenesis of psoriasis and, as a consequence, new therapies. Defining the molecular genetics of psoriasis will enhance our understanding of the disease process and hopefully facilitate the development of a representative animal model. This in itself will be a key step in the development and testing of new therapies. Precise identification of the immunological events involved in psoriasis will allow specific T-cell- and cytokine-targeted, and perhaps less toxic. immunotherapies. Anti-angiogenic agents that are in development for use in oncology may also be effective in psoriasis. The adaptation of current topical therapies such as retinoids and vitamin D analogues to produce more effective and better-tolerated formulations will also play a significant role in our future first-line management of patients. The increased recognition and better management of environmental trigger factors such as psychological distress will become an important factor in future psoriasis care. The development of physical therapies including photodynamic therapy and excimer lasers has the potential to expand the remit of psoriasis therapy. There is little doubt that the future for our patients with psoriasis is bright. However, this will only be achievable by a concerted research effort to understand all facets of this enigmatic disease ranging from the molecular to the environmental.

Exogenous topical lactoferrin inhibits allergen-induced Langerhans cell migration and cutaneous inflammation in humans

BACKGROUND

Lactoferrin (LF), an iron-binding protein found in exocrine secretions, is known to possess antibacterial properties. It has recently been proposed that LF may also influence inflammatory reactions.

OBJECTIVES

To characterize in humans the ability of recombinant homologous LF to inhibit the induced migration of epidermal Langerhans cells (LCs) from the skin, a process known to be dependent upon the proinflammatory cytokines tumour necrosis factor (TNF)-alpha and interleukin 1beta and to influence cutaneous inflammatory reactions.

METHODS

We investigated the anti-inflammatory properties of LF in human volunteers.

RESULTS

Topical exposure to LF 2 h prior to sensitization caused a significant reduction in contact allergen (diphenylcyclopropenone, DPC)-induced LC migration from the epidermis as judged by the altered frequency of cells expressing either HLA-DR or CD1a determinants. That this reduction was secondary to an inhibition of TNF-alpha production was indicated by the fact that LF failed to influence LC migration induced by intradermal injection of this cytokine. In approximately 50% of those volunteers who displayed local inflammation in response to DPC, LF was found to cause a discernible reduction in the clinical severity of the reaction, associated with reduced infiltration of inflammatory cells.

CONCLUSIONS

These data demonstrate that LF is able to influence cutaneous immune and inflammatory responses, possibly because of an impaired production of local proinflammatory cytokines.

Distribution and expression of type VI collagen in photoaged skin

BACKGROUND

Several of the characteristic clinical features of photoaged skin, including wrinkling, are thought to be dependent on changes in the dermal matrix brought about by chronic sun exposure. Such changes include reductions in collagens I, III and VII, an increase in elastotic material in the reticular dermis and a marked reduction in the microfibrillar glycoprotein fibrillin.

OBJECTIVES

To examine whether type VI collagen, a microfibrillar collagen necessary for cell-cell and cell-matrix communication, is affected by the photoageing process.

METHODS

Six healthy volunteers with moderate to severe photoageing were enrolled into the study. Immunohistochemistry and in situ hybridization histochemistry were used to examine the levels of type VI collagen in photoprotected and photoaged sites.

RESULTS

In photoprotected skin, type VI collagen was concentrated in the papillary dermis immediately below the dermal-epidermal junction, around blood vessels, hair follicles and glandular structures. The distribution of type VI collagen was unchanged in photoaged skin, although we observed an increase in the abundance of the alpha3 chain of collagen VI in the upper papillary dermis, at its junction with the dermal-epidermal junction (P < 0.05). No alterations were observed for any alpha chain at the mRNA level.

CONCLUSIONS

These studies suggest that chronic sun exposure (photoageing) has little or no effect on either the distribution, abundance or levels of expression of type VI collagen in human skin. Thus, type VI collagen, unlike other matrix components so far studied, appears to be relatively unaffected by the photoageing process.

Topical tacrolimus in the management of peristomal pyoderma gangrenosum

BACKGROUND

Peristomal pyoderma gangrenosum (PPG) is a potentially disabling disease in stoma patients. Topical tacrolimus has been shown to be effective in the management of pyoderma gangrenosum. Unfortunately, greasy topical treatments may be impractical for PPG because of impaired appliance adhesion.

OBJECTIVE

The purpose of this open study was to evaluate the therapeutic effectiveness of topical tacrolimus 0.3% formulated in carmellose sodium paste compared with topical corticosteroid preparations in the management of PPG.

RESULTS

A total of 11 patients with PPG received treatment with topical tacrolimus 0.3% in Orabase trade mark and 13 with topical clobetasol propionate 0.05% as monotherapy in each case. Seven of the tacrolimus-treated group healed completely (mean time to healing: 5.1 weeks) compared with five of the clobetasol propionate-treated group (mean time to healing: 6.5 weeks). Topical tacrolimus was significantly more effective than clobetasol propionate in managing larger PPG lesions (ulcer diameter > 2 cm). In six patients, who had failed to respond adequately to multiple systemic and topical treatments for PPG, the addition of topical tacrolimus was associated with healing of PPG within 6 weeks.

CONCLUSION

These results suggest that topical tacrolimus 0.3% in Orabase trade mark is a more effective and expeditious treatment than clobetasol propionate 0.05% for PPG. It is significantly more effective than clobetasol propionate 0.05% in managing lesions larger than 2 cm in diameter. Topical tacrolimus may be highly effective when other systemic or topical treatments have been unsuccessful.

Successful treatment of severe recalcitrant psoriasis with combination infliximab and methotrexate

Plaques of psoriasis contain increased levels of cytokines, including tumour necrosis factor-alpha (TNF-alpha), which are thought to be essential to the maintenance of the psoriatic process. We report the successful treatment of severe, recalcitrant psoriasis when infliximab (a monoclonal antibody to TNF-alpha) was used in combination with methotrexate.

The contribution of perceptions of stigmatisation to disability in patients with psoriasis

OBJECTIVE

The aim of the present study was to assess the significance of general and psoriasis specific psychological variables in patients with psoriasis and to examine the relative importance of disease status and these psychological variables in predicting psoriasis-related disability.

METHOD

A total of 115 patients with psoriasis underwent clinical assessment and completed a number of psychological and psoriasis specific questionnaires.

RESULTS

High levels of self-reported distress were identified with 43% and 10% of patients scoring as probable cases on the Hospital Anxiety and Depression Scale (HADS) subscales of anxiety (mean 9.3+/-4.9) and depression (mean 4.8+/-3.7), respectively. Multiple regression analysis indicated that clinical severity of psoriasis and anatomical area of involvement had no impact on psychological distress and disability. Perceptions of stigmatisation were significantly related to both psychological distress and degree of disability (P's<.001) and accounted for a significant amount of the variance in disability over and above general psychological distress (F change=11.03; P<.001).

CONCLUSION

Psychological factors were much stronger determinants of disability in patients with psoriasis than disease severity, location or duration. This has important implications in relation to the clinical management of psoriasis.

Combination regimens of topical calcipotriene in chronic plaque psoriasis: systematic review of efficacy and tolerability

OBJECTIVE

To examine the efficacy and tolerability of calcipotriene combined with phototherapy or systemic therapies compared with monotherapy for the treatment of chronic plaque psoriasis.

DESIGN

Quantitative systematic review of 11 randomized controlled trials involving a total of 756 patients with plaque psoriasis.

MAIN OUTCOME MEASURES

Rate ratios (RRs) for marked improvement or clearance in patient and investigator overall assessments of response; mean difference in percentage change in Psoriasis Area and Severity Index; and RRs for clearance in patient and investigator overall assessments of response. Adverse effects were estimated with the RR and the rate difference in terms of withdrawal rate, proportion of patients experiencing adverse events, and proportion of patients with cutaneous and noncutaneous adverse effects.

RESULTS

Antipsoriatic effects of acitretin, cyclosporine, and psoralen-UV-A phototherapy were enhanced with the addition of topical calcipotriene using the Psoriasis Area and Severity Index as the outcome, but this is not translated into an increase in the number of patients who achieve at least marked improvement. At the end of treatment, the RRs for marked improvement or clearance in patient assessments were as follows: calcipotriene plus acitretin vs acitretin alone (12 weeks), 1.4 (95% confidence interval [CI], 1.0-1. 9); calcipotriene plus cyclosporine vs cyclosporine alone (6 weeks), 1.2 (95% CI, 0.9-1.6); and calcipotriene plus psoralen-UV-A vs psoralen-UV-A alone (12 weeks), 1.2 (95% CI, 0.9-1.6). Patients were also no more likely to obtain marked improvement or better with calcipotriene plus UV-B therapy than with UV-B therapy alone (RR, 1. 0; 95% CI, 0.8-1.1 at 8 weeks in the patient assessment). There is limited evidence that use of calcipotriene might reduce the cumulative exposure to phototherapy and systemic treatment. During the short duration of these trials, there were no significant differences in withdrawal rates or adverse effects between the combined regimens and their corresponding monotherapy control interventions.

CONCLUSIONS

Overall, there is insufficient evidence to support any large effects in favor of combination treatment. In the patient assessments, the results do not show an adjuvant effect, but there is some evidence that use of calcipotriene might reduce cumulative exposure to systemic therapy to obtain clearance. There were no long-term morbidity data on the effectiveness of any of the combinations studied. Given that psoriasis is a chronic recurrent disease for most patients, longer trials are needed to determine whether the addition of topical calcipotriene to systemic therapy improves the risk-benefit ratio by reducing the long-term risk of toxic effects. Equally important is the need to examine the impact of such combinations on the duration of remission after treatment.

The spectrum of skin disorders in abdominal stoma patients

BACKGROUND

Skin integrity is essential for the normal usage of a stoma appliance. However, there is little published on the prevalence, nature or management of stoma-related skin disorders. Objectives To document stoma-related skin disorders in a large cohort of patients.

METHODS

We sent a postal questionnaire to all surviving patients who had had abdominal stoma surgery at Hope Hospital, Salford, U.K. in the 10 years from 1 January 1989. Those reporting skin disease were invited to attend a clinic run by a dermatologist and a stoma-care specialist nurse. All lesions were categorized and swabs taken for microbiological examination.

RESULTS

Of 525 surviving patients, 325 (62%) replied to the questionnaire. Of these, 73% reported a skin problem that had affected normal stoma bag use. Dermatoses included irritant reactions, particularly from leakage of urine or faeces (42%); pre-existing skin diseases, principally psoriasis, seborrhoeic dermatitis and eczema (20%); infections (6%); allergic contact dermatitis (0.7%) and pyoderma gangrenosum (0.6% annual incidence). A further 15% of patients with skin problems had persistent or recurrent dermatitis not explained by allergy, frank infection or faecal irritation. This responded to short-term treatment with topical corticosteroids. Further investigation is under way into its pathogenesis.

CONCLUSIONS

Skin disorders are common in stoma patients, and various patterns can be recognized and effectively treated.

Investigation of cytomegalovirus and human herpes viruses 6 and 7 as possible causative antigens in psoriasis

Psoriasis is probably a T-cell-mediated autoimmune disease. Infectious models of autoimmune diseases have been proposed and in psoriasis, it has been suggested that there may be molecular mimicry between streptococcal antigens and epidermal keratins. The immunological profile of stable psoriasis plaques suggests, however, that viral antigens may be important. We investigated, using polymerase chain reaction techniques, whether DNA from either cytomegalovirus (CMV) or human herpes viruses (HHV) 6 and 7 is present in the skin of patients (n = 10) with chronic plaque psoriasis. We also investigated 29 patients for the presence of serum IgG to CMV. We found no evidence of CMV or HHV 7 DNA in psoriasis plaques although DNA for HHV 6 was detected in both involved and uninvolved skin in 1 out of 10 patients. There was no statistically significant increase in prior CMV infection, as assessed by the presence or absence of serum IgG to CMV, in psoriasis, compared to our local population. Although there is circumstantial evidence that viral antigens may be important in the pathogenesis of psoriasis we found no evidence to link infection with CMV or HHV 6 and 7 with subsequent development of chronic plaque psoriasis.

Cost-effectiveness analysis of topical calcipotriol versus short-contact dithranol. In the treatment of mild to moderate plaque psoriasis

OBJECTIVE

To examine the relative cost effectiveness of topical calcipotriol and short-contact dithranol in the treatment of mild to moderate plaque psoriasis.

DESIGN AND SETTING

This was a modelling study from the perspective of the UK National Health Service as payer.

METHODS

The interventions were compared using 2 decision-analytic models: one using a short term horizon (12 weeks) and the other using a longer term horizon (up to 1 year). Clinical success of treatment and relapse rates were obtained from the results of randomised controlled trials.

MAIN OUTCOME MEASURES AND RESULTS

The outcome measure used was the degree of improvement in psoriasis as judged by the patient. In the short term comparison, calcipotriol was the most effective treatment (60.8% success), but it was also the most expensive (96.03 Pounds; 2000 values). The incremental cost per success was 577.50 Pounds using a 12-week course of calcipotriol compared with short-contact dithranol. Over the long term horizon, first-line treatment with calcipotriol still had the highest expected cost per successful treatment (164.91 Pounds), but the incremental cost using this strategy was 38.66 Pounds compared with short-contact dithranol. In terms of cost per successful day's treatment (i.e. the cost for a day in which the patient reported a marked improvement or cleared lesions), the cost of each additional successful day's treatment was 19.93 Pounds when using calcipotriol as first-line treatment rather than short-contact dithranol.

CONCLUSION

The combination of differences in drug acquisition costs and relapse rates can lead to large differences in the comparative cost effectiveness of topical treatments for plaque psoriasis. From the perspective of the prescriber, the results of this analysis suggest that selecting short-contact dithranol as first-line treatment was the most cost-effective strategy.

Topical sucralfate in the management of peristomal skin disease: an open study

Dermatoses affecting the skin around stoma sites are common and difficult to treat. We have investigated the effectiveness of topical sucralfate in the management of peristomal dermatoses in adults using an open study design. Apart from forming a physical barrier to further irritation, sucralfate binds to basic fibroblast growth factor preventing its degradation and thereby promotes healing. In eight out of nine patients with faecal or urine erosions, daily, topical sucralfate treatment was associated with healing within 4 weeks. There was limited or no response to treatment in a further nine patients with traumatic ulcers, excoriated dermatitis or pyoderma gangrenosum. Topical sucralfate represents a safe, inexpensive and effective therapeutic intervention, particularly for those patients with high output or short stomas where repeated stoma leakage may be unavoidable.

Peristomal dermatoses: a novel indication for topical steroid lotions

BACKGROUND

Dermatoses that interfere with the normal use of a stoma appliance are common. When preventable causes, such as infection or allergy, are not identified, barrier preparations or topical steroids have been used. However, topical medicaments formulated in a cream or ointment base will cause stoma bags to detach, resulting in leaks.

OBJECTIVE

Our purpose was to investigate the efficacy and suitability of corticosteroids in aqueous/alcohol lotions in the management of peristomal dermatoses.

METHODS

A clinic run by a dermatologist and 2 stoma nurses was created. Patients with a variety of noninfective, inflammatory dermatoses were treated with topical corticosteroid lotions up to a maximum of 4 weeks, with occasional use thereafter in some cases.

RESULTS

Topical, aqueous/alcohol, corticosteroid lotions have been used in 60 patients and have proved particularly useful for the treatment of irritant dermatitis, pyoderma gangrenosum, psoriasis, and constitutional eczema. After the initial treatment course, occasional applications, approximately every 2 weeks, may be necessary to control the skin disorder. This low frequency of application minimizes the risk of side effects so that we have not identified local or systemic side effects in any of the patients treated so far.

CONCLUSION

Topical corticosteroids formulated in aqueous alcohol lotion are effective and acceptable treatments for peristomal dermatoses. If used appropriately, the risk of side effects is low.

Basal cell carcinoma

BACKGROUND

Basal cell carcinoma (BCC) is characterized by marked interpatient variation in tumor accrual. The authors previously reported that presentation with a cluster of BCC is associated with an inherited predisposition to develop many additional lesions suggesting clustering is a critical event. A cluster is defined as the presence of two or more new, primary BCCs, at initial or later presentation.

METHODS

The authors recruited 927 cases and determined whether 1) clustering was an early or late event and 2) tumor accrual was altered after clustering.

RESULTS

In the cases, 669 patients developed only 1 lesion, 112 patients presented more than once but with single lesions (single presentation phenotype[SPP]-more), 94 cases had a cluster at first presentation (multiple presentation phenotype [MPP]-cluster initial), and 52 cases first presented with 1 lesion but later had a cluster (MPP-cluster later). The authors found that 1) clustering occurred relatively late. The mean ages at first presentation with 1 BCC of the SPP-more (61.5 years) and MPP-cluster later patients (60.4 years) were similar although presentations with clusters in the MPP-cluster initial (67.6 years, P = 0.0002) and -cluster later cases (68.1 years, P = 0.002) occurred significantly later. 2) Clustering was associated with increased accrual. Thus, 26 patients (MPP-cluster later/a) in the MPP-cluster later group had a additional BCC postcluster. Mean accrual post-cluster (1.99 BCC/year) in these cases was significantly increased (P = 0.0001) compared with precluster accrual (0.39 BCC/year).

CONCLUSIONS

The authors found that the formation of BCC clusters represents a critical event such that after a cluster presentation, tumor accrual is significantly increased. Cluster presentation is a relatively late event suggesting reduced effectiveness in immune surveillance.

Langerhans cell migration

Epidermal Langerhans cells (LC) play pivotal roles in the induction of cutaneous immune responses. Encounter with antigen in the skin, or other stimuli, cause the mobilization of LC and their migration, via afferent lymphatics, to draining lymph nodes where they localize within the paracortex. During their movement from the skin LC acquire the characteristics of immunostimulatory dendritic cells (DC) such that the antigen-bearing cells which accumulate in lymph nodes are able to provoke specific T-lymphocyte responses. Epidermal cytokines initiate and regulate LC migration (and maturation), of particular importance being interleukin-1beta and tumour necrosis factor-alpha. Collectively, these cytokines, together with relevant chemokine receptor-ligand interactions, effect the liberation of LC from the epidermis and their directed movement to, and localization within, peripheral lymph nodes. Described here are the phenotypic changes induced during the activation of LC and the mechanisms through which their migration is regulated.