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R J Dearman

Publications and source records attributed to R J Dearman.

At least 91 records · Page 5Linked to original sources
PubMed1998

Characteristics and regulation of the expression on interleukin 1 receptors by murine Langerhans cells and keratinocytes.

There is increasing evidence that interleukin 1beta (IL-1beta), a product in murine epidermis of Langerhans cells (LC) exclusively, contributes to the initiation and regulation of LC migration in response to skin sensitization. The hypothesis is that IL-1beta induces the production by keratinocytes of tumour necrosis factor alpha (TNF-alpha) which acts in a paracrine fashion on LC to provide one signal for migration. In addition, it is believed that IL-1beta acts in an autocrine fashion on LC to provide a second, TNF-alpha-independent, signal for the initiation of this response. The viability of this hypothesis is dependent upon the availability of appropriate membrane receptors. We describe therefore experiments designed to investigate the IL-1 receptor (IL-1R) status of keratinocytes, LC and lymph node dendritic cells (DC). Flow cytometric analyses of epidermal cell suspensions revealed at least 60% of LC positive for the type I IL-1R (IL-1RI). In contrast, only a small proportion of keratinocytes displayed surface IL-1RI, although high intracellular expression of this receptor could be detected either by flow cytometric analysis of cells permeabilized with saponin or by immunofluorescence microscopy. Expression of the type II IL-1R (IL-1RII) was detected at relatively low levels on both LC and keratinocytes. Interestingly, DC isolated from the lymph nodes of sensitized mice displayed upregulated expression of IL-1RI and lower levels of IL-1RII compared to LC. The conclusion drawn is that the IL-1R phenotype of LC and keratinocytes under resting conditions is consistent with the proposed contribution of IL-1beta to LC migration. Furthermore, the regulation of IL-1R expression by epidermal cells and DC will undoubtedly influence the development of cutaneous immune responses.

Animals↗
PubMed1998

Differential regulation by thalidomide and dexamethasone of cytokine expression in human peripheral blood mononuclear cells.

Immunosuppressive drugs are used routinely to reduce the inappropriate production of cytokines in an immune response. Recent attention has focused on drugs that selectively inhibit specific cytokines. Both thalidomide and dexamethasone have been reported to exhibit immunomodulatory effects on cytokines in vitro. We wished to examine the effects of thalidomide and dexamethasone on the production of cytokines by peripheral blood mononuclear cells (PBMC), following mitogenic stimulation, at the level of both secreted product and mRNA production. PBMC from healthy human volunteers were stimulated optimally with phytohaemagglutinin (PHA) in the presence of varying concentrations of thalidomide and dexamethasone using dimethyl sulphoxide (DMSO) as the solvent. Analysis of supernatants by enzyme-linked immunosorbent assay (ELISA) showed that thalidomide caused a dose-dependent inhibition of the pro-inflammatory cytokines interleukin 6 (IL-6) and tumour necrosis factor alpha (TNF-alpha), maximally reducing production by 20 (P < 0.05) and 30% (P < 0.01), respectively, compared with controls. However, thalidomide did not affect either proliferation or the production of interleukin 2 (IL-2), interleukin 4 (IL-4) or interleukin 10 (IL-10). A slight bell shaped inhibition of interferon gamma (IFN-gamma) was seen which was statistically significant (P < 0.05). In contrast, dexamethasone inhibited markedly the expression of all cytokines tested (IL-2, IL-4, IL-6, IL-10, IFN-gamma and TNF-alpha) in dose-dependent fashion, reducing levels to near to background. Reverse transcription-polymerase chain reaction (RT-PCR) analyses showed that thalidomide inhibited selectively the expression of TNF-alpha and IL-6 mRNA, whereas dexamethasone inhibited mRNA levels of all cytokines examined. The data indicate that dexamethasone is a broad range immunosuppressant inhibiting all cytokines tested in a dose-dependent manner at the level of both secreted product and mRNA. Conversely, thalidomide selectively inhibits the production of IL-6 and TNF-alpha. Due to their markedly different effects on cytokine production, and the fact that both drugs act at the level of transcription, we believe they influence separate pathways involved in cytokine gene regulation.

Anti-Inflammatory Agents↗
PubMed1998

Selective induction of type 2 cytokines following topical exposure of mice to platinum salts.

Repeated topical exposure of BALB/c strain mice to organic chemical respiratory allergens, such as trimellitic anhydride (TMA), or contact allergens such as 2,4-dinitrochlorobenzene (DNCB), provokes characteristic cytokine secretion profiles consistent with the divergent activation of discrete T cell subpopulations. Under such conditions, lymph node cells (LNC) isolated from animals exposed to TMA elaborated comparatively large amounts of the type 2 cytokines interleukin 10 (IL-10) and mitogen-inducible interleukin 4 (IL-4), but only low levels of the type 1 product interferon gamma (IFN-gamma). In contrast, DNCB-activated LNC displayed the converse (type 1) cytokine secretion profile. We have now examined cytokine production induced by topical application to mice of respiratory sensitizing platinum salts; ammonium tetrachloroplatinite II, ammonium hexachloroplatinate IV and cis-dichlorodiammine platinum II. Metal salts were dissolved in dimethyl sulfoxide (DMSO). Cytokine secretion profiles were compared with those elicited following concurrent exposure to TMA or DNCB or to the vehicle acetone:olive oil (AOO) alone. All three platinum salts and TMA stimulated vigorous IL-4 and IL-10 production compared with DNCB-activated LNC; vehicle-stimulated LNC failed to elaborate detectable levels of either cytokine. However, DNCB and the DMSO vehicle provoked substantial IFN-gamma expression, whereas exposure to AOO vehicle resulted in a considerably weaker IFN-gamma response. Levels of this cytokine induced by treatment with respiratory allergens were, in the majority of cases, substantially lower than those observed with the relevant vehicle. Indeed, an inverse dose-response relationship for IFN-gamma expression was exhibited by all three platinum salts, suggestive of the elaboration by platinum salt activated LNC of an inhibitory factor or factors for IFN-gamma. These data suggest that it may be possible to identify those metal salts with respiratory sensitizing potential as a function of induced type 2 cytokine secretion patterns.

Administration, Topical↗
PubMed1998

Langerhans cells and chemical allergy.

Epidermal Langerhans cells (LCs) play a pivotal role in the induction of cutaneous immune responses, including those provoked by chemical allergens. The delivery by LCs of allergen to draining lymph nodes requires cell migration from the skin, a process that is dependent upon the availability of epidermal cytokines -particularly TNF-alpha and IL-1beta. Here we consider the ways in which these cytokines interact with LCs to both induce and regulate their mobilization in response to skin sensitization. In addition, the effects of these cytokines on both the selectivity of LC migration from the skin and protection of LCs from cell death are considered. Finally, the possible counter-regulatory activity of other cutaneous cytokines and the influence of LCs on the development of selective T lymphocyte responses are explored.

Allergens↗
PubMed1998

Cytokine production by CD4+ and CD8+ T cells in mice following primary exposure to chemical allergens: evidence for functional differentiation of T lymphocytes in vivo.

It has been demonstrated previously that repeated exposure of mice to chemical allergens of different types results in the development of qualitatively divergent immune responses characterized by the production by draining lymph node cells (LNC) of distinct cytokine patterns. Chronic exposure of mice to contact allergens, such as 2,4-dinitrochlorobenzene (DNCB), resulted in the secretion by LNC of low or undetectable levels of interleukins 4 and 10 (IL-4 and IL-10), but comparatively high levels of interferon gamma (IFN-gamma); the latter cytokine being produced by both CD4+ and CD8+ cells. In contrast, chronic exposure of mice to trimellitic anhydride (TMA), a respiratory allergen associated in humans with occupational asthma, induced instead the production by LNC of relatively high concentrations of IL-4 and IL-10, but little IFN-gamma. The low levels of IFN-gamma secretion which were provoked by treatment with TMA were shown to derive from CD8+ cells exclusively. In the present investigations we have sought to determine whether the polarized responses observed following repeated exposure to these chemical allergens are reflected by cytokine secretion patterns provoked by primary exposure. To this end, mice of BALB/c strain were exposed epicutaneously daily for 3 consecutive days to concentrations of DNCB and TMA (1 and 10%, respectively), or to oxazolone, another contact allergen (0.25%), that resulted in substantial proliferative activity in draining lymph nodes. The production by draining LNC of IFN-gamma and of mitogen-inducible IL-4 was measured by enzyme-linked immunosorbent assay and the relative contribution of CD4+ and CD8+ cells to the patterns of cytokine secretion observed was analyzed using both positive and negative selection methods. It was found that primary exposure to DNCB, oxazolone and TMA each resulted in the production by LNC of both IFN-gamma and IL-4. Selective depletion of, or enrichment for, CD4+ and CD8+ cells revealed that only CD4+ cells elaborated mitogen-inducible IL-4. Depletion of neither CD4+ nor CD8+ cells compromised the production by TMA- or DNCB-activated LNC of IFN-gamma, although positively selected CD8+ cells were considerably less able than CD4+ cells to elaborate this cytokine, presumably secondary to a lack of appropriate accessory cells. Taken together the results demonstrate that early during immune responses to DNCB or oxazolone and TMA there is no evidence for the selectivity of cytokine secretion patterns that characterizes responses following more chronic exposure. Moreover, it is clear that exposure to TMA initially induces the production of IFN-gamma by both CD4+ and CD8+ cells, whereas after more chronic treatment the secretion of this cytokine is a function of CD8+ cells exclusively. Collectively, these results indicate that the polarized responses that develop in mice following chronic exposure to different classes of chemical allergen are not reflected by the characteristics of primary immune responses. As such the development of qualitatively divergent immune responses to chemical allergens provides a paradigm for the evolution of differentiated T cell function with time and/or with antigen exposure.

Allergens↗
PubMed1998

Estimation of relative skin sensitizing potency using the local lymph node assay: a comparison of formaldehyde with glutaraldehyde.

BACKGROUND: Chemicals vary considerably in their intrinsic ability to cause allergic contact dermatitis. Presently, there are no experimental methods available for the quantitative assessment of the relative sensitizing potency of chemical allergens. OBJECTIVE: The objective of the investigations described here was to evaluate the use of the local lymph node assay for determining the relative skin sensitizing potential of chemicals. This has been addressed by comparing the sensitizing potency of formaldehyde with glutaraldehyde. METHODS: Dose responses induced by formaldehyde and glutaraldehyde in the local lymph node assay, using either acetone or dimethylformamide (DMF) as the application vehicle, have been measured. Relative skin sensitizing potency was estimated as a function of the amount of chemical required to induce a threefold increase in lymph node cell proliferative activity, a mathematically derived EC3 value (estimated concentration required to induce a stimulation index of 3). RESULTS: In both vehicles, glutaraldehyde induced substantially more vigorous responses in the local lymph node assay (EC3 values of 0.006mol/L in acetone and 0.002mol/L in DMF) than did formaldehyde (EC3 values of 0.18mol/L in acetone and 0.11mol/L in DMF). CONCLUSIONS: These results demonstrate that glutaraldehyde has a considerably greater potential to induce skin sensitization than does formaldehyde; the data are consistent with what is known of the ability of these chemicals to cause allergic contact dermatitis in humans. Using formaldehyde and glutaraldehyde as examples, the results here illustrate the utility of EC3 values derived from local lymph node assay responses for the estimation of the relative potency of skin sensitizing chemicals.

Allergens↗
PubMed1998

Lack of association between interleukin-6 production by contact allergen-activated draining lymph node cells and lymphoproliferative activity.

BACKGROUND: Previous investigations in BALB/c strain mice have revealed that, after skin sensitization, draining lymph node cells (LNC) produce high levels of interleukin 6 (IL-6) and that the secretion of this cytokine correlates closely with the proliferative activity of LNC. The main source of IL-6 within draining lymph nodes was found to be dendritic cells (DC), most of which derive from epidermal Langerhans cells. OBJECTIVE: To explore further the relationship between DC-derived IL-6 production in lymph nodes, LNC proliferative activity, and the development of contact sensitization, comparisons between BALB/c and C3H/HeN strains of mice have been conducted. METHODS: Contact sensitizing potential was measured in both strains of mice as a function of lymphocyte proliferative responses (assessed by the incorporation of radiolabelled thymidine) and challenge-induced increases in ear thickness. The concentration of IL-6 in skin homogenates and the production of IL-6 by allergen-activated LNC were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: In both strains of mouse, topical exposure to oxazolone, a potent contact allergen, induced a vigorous proliferative response by draining LNC and the development of skin sensitization. However, under these conditions of exposure, activated LNC prepared from mice of C3H/HeN strain failed to secrete substantial amounts of IL-6, the levels of this cytokine being on average some 20- to 40-fold less than those measured in BALB/c mice. The failure of LNC from C3H/HeN mice to secrete comparable levels of IL-6 was not attributable to a reduced ability of DC to accumulate in draining lymph nodes after skin sensitization. Nor did reduced IL-6 secretion by C3H/HeN LNC reflect a systemic inability to elaborate this cytokine. Epicutaneous exposure of C3H/HeN mice to oxazolone resulted in the induction of cutaneous IL-6 at levels similar to, or greater than, those observed after identical treatment of BALB/c strain mice. CONCLUSIONS: The conclusion drawn is that there does not exist a universal association between IL-6 production in draining lymph nodes and the vigor of proliferative responses by LNC. Further, cutaneous immune responses and skin sensitization may proceed apparently normally in the absence of high levels of IL-6 production by lymph node cells.

Allergens↗
PubMed1997

Interleukin 1 beta and the stimulation of Langerhans cell migration: comparisons with tumour necrosis factor alpha.

Epidermal Langerhans cells (LC) and the cells into which they mature are believed to play a pivotal role in cutaneous immune function. The induction phase of contact sensitization is associated with the migration of LC from the skin and their accumulation as dendritic cells (DC) in lymph nodes draining the site of exposure. We have demonstrated previously that tumour necrosis factor alpha (TNF-alpha), an epidermal cytokine produced by keratinocytes, provides one signal for LC migration. We describe here experiments designed to evaluate the influence of interleukin 1 beta (IL-1 beta), a product exclusively of LC in murine epidermis, on LC migration, LC morphology and DC accumulation, and to compare the effects of this cytokine with those of TNF-alpha. Both cytokines induced a significant reduction in the frequency of epidermal LC and the arrival of DC in draining lymph nodes. Changes in both parameters were induced more rapidly following intradermal administration of TNF-alpha than were observed after treatment with IL-1 beta. However, the reduction in LC frequency was more persistent with IL-1 beta. Both cytokines caused the activation of LC, characterized by the acquisition of a more dendritic morphology and the increased expression of Ia molecules. These results demonstrate that IL-1 beta and TNF-alpha can each stimulate the migration of epidermal LC, but that the changes induced by these cytokines are not identical.

Animals↗
PubMed1997

A re-appraisal of the skin-sensitizing activity of 2,4-dinitrothiocyanobenzene.

A debate continues regarding the immunological properties of 2,4-dinitrothiocyanobenzene (DNTB). In some investigations this chemical was shown not to cause skin sensitization when applied topically but to induce instead hyporesponsiveness or immunological tolerance. In other studies DNTB was found to cause skin sensitization, but not tolerance. However, this chemical continues to be used to discriminate between the properties of skin sensitizing and non-sensitizing chemicals. This study demonstrates that topical exposure of mice to DNTB induces skin sensitization in mice and that this is associated with the accumulation of dendritic cells in draining lymph nodes and the stimulation of lymph node cell proliferation; the latter responses being of equivalent magnitude to those stimulated by 2,4-dinitrochlorobenzene (DNCB), a chemical known to cause contact sensitization. Moreover, exposure of mice to DNTB, as with exposure to DNCB, resulted in the development of a cytokine secretion pattern by draining lymph node cells (LNC) characteristic of contact allergens. Thus, DNTB and DNCB each induced the production by LNC of high levels of interferon-gamma, but little or no interleukin 4 or interleukin 10. Finally, DNTB was shown in the guinea pig maximization test to behave as an extreme skin sensitizer. These results confirm that DNTB should not be regarded as a universal tolerogen and that it possesses a significant potential to induce contact sensitization. The use of this chemical as a presumptive non-sensitizer and/or tolerogen for the evaluation of the selectivity of new predictive test methods for the identification of contact allergens is therefore considered to be inappropriate.

Administration, Topical↗
PubMed1997

Characteristics of antibody responses induced in mice by protein allergens.

Whereas many foreign proteins are immunogenic, only a proportion is also allergenic, having the capacity to induce the quality of immune response necessary to support the production of IgE antibody. We have demonstrated previously that intraperitoneal administration to mice of proteins such as ovalbumin (OVA) or the industrial enzyme A. oryzae lipase, which possess significant allergenic potential, stimulates the production of both IgG and IgE antibody. Identical exposure to bovine serum albumin (BSA), a protein with limited potential to cause immediate respiratory or gastrointestinal hypersensitivity reactions, induced IgG responses only. In the current investigations, the quality of immune responses induced following exposure to these proteins via mucosal tissue (intranasal) has been compared with those provoked following administration via a non-mucosal (intraperitoneal) route of exposure. Intranasal or intraperitoneal administration of BSA, OVA or A. oryzae lipase elicited in each case vigorous IgG and IgG1 antibody responses. For all three proteins, at every concentration tested, and via both routes of exposure, IgG1 antibody titres paralleled closely IgG titres. However, the three materials displayed a differential potential to provoke IgE responses and this correlated with their known allergenic potential in humans. Thus, OVA and A. oryzae lipase stimulated strong IgE antibody responses, whereas BSA provoked low titre IgE only at the highest concentration tested (5% administered intraperitoneally). The quality of induced responses was not affected by the route of exposure. It would appear, therefore, that the stimulation of IgG and IgG1 antibody responses is a reflection of protein immunogenicity whereas protein allergenicity is associated with the induction of strong IgE responses.

Administration, Intranasal↗
PubMed1997

Langerhans cells require signals from both tumour necrosis factor-alpha and interleukin-1 beta for migration.

The induction phase of contact sensitization is associated with the movement of epidermal Langerhans cells (LC) from the skin and their migration, via afferent lymphatics, to draining lymph nodes where they accumulate as immunostimulatory dendritic cells (DC). It has been demonstrated previously that tumour necrosis factor-alpha (TNF-alpha) provides an important signal for LC migration and that in the absence of this cytokine, movement of LC from the epidermis to regional lymph nodes is inhibited. Recent evidence indicates that interleukin-1 beta (IL-1 beta), a cytokine produced in murine epidermis exclusively by LC, may also play a role in LC migration. The purpose of the investigations described here was to clarify, using relevant neutralizing anti-cytokine antibodies, the contributions made by TNF-alpha and IL-1 beta to the migration of LC from the epidermis. It was found that like anti-TNF-alpha, anti-IL-1 beta administered systemically to mice (by intraperitoneal injection), prior to skin sensitization with the contact allergen oxazolone, resulted in a marked inhibition of DC accumulation in draining lymph nodes. It was shown also that anti-IL-1 beta inhibited TNF-alpha-induced LC migration and DC accumulation and that; in similar fashion, the stimulation of LC migration and DC accumulation induced by IL-1 beta was compromised by prior treatment with anti-TNF-alpha. Based upon these data it is proposed that the stimulation of LC migration in response to skin sensitization requires the receipt by LC of two independent signals, one provided by TNF-alpha and the other by IL-1 beta. Morphological analyses of LC in epidermal sheets prepared from animals exposed to these cytokines with or without prior systemic treatment with anti-cytokine antibody suggested that the changes induced in LC by TNF-alpha and IL-1 beta may include the altered expression of adhesion molecules and acquisition of the ability to interact with and pass through the basement membrane.

Animals↗
PubMed1997

Dinitrohalobenzenes: evaluation of relative skin sensitization potential using the local lymph node assay.

The dinitrohalobenzenes are known to cause skin sensitization and have been used in many seminal investigations of the relationships between physicochemical characteristics and sensitizing potential. The electrophilic theory of skin sensitization implies that contact allergic potential should correlate positively with ability of chemicals to react with proteins to form immunogenic hapten-protein conjugates. It is intriguing, therefore, that previous studies in guinea pigs and mice have suggested that such correlations do not apply to dinitrohalobenzenes. To address this, we have examined, using the murine local lymph node assay (LLNA), the sensitizing activity of 2,4-dinitrofluorobenzene (DNFB), 2,4-dinitrochlorobenzene (DNCB), 2,4-dinitrobromo-benzene (DNBB) and 2,4-dinitroiodobenzene (DNIB). In contrast to previous investigations, it was found that the ability of these chemicals to provoke responses in the LLNA correlated closely with their reported protein reactivity. On the basis of these data, it is proposed that dinitrohalobenzenes conform to the electrophilic theory of skin sensitization and that they should be regarded as direct acting haptens.

Allergens↗
PubMed1997

Differential induction of cutaneous TNF-alpha and IL-6 by topically applied chemicals.

BACKGROUND: Increasing evidence shows that contact allergens and skin irritants can induce or upregulate the cutaneous expression of cytokines, including those that are required for the initiation of immune responses and which participate in inflammatory reactions. OBJECTIVE: The present investigation compared the ability of the skin allergens oxazolone and 2,4-dinitrochlorobenzene (DNCB) and the skin irritant benzalkonium chloride (BZC) to stimulate the cutaneous expression of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) in mice. RESULTS: Each chemical tested induced the dose-dependent production of IL-6 with similar kinetic profiles. BZC was less effective at provoking increases in this cytokine; concentrations (1%) that caused marked edema failed to stimulate significant changes in IL-6 expression. Under conditions of topical exposure in which each of these chemicals caused a vigorous inflammatory response in the skin, as measured by induced edema and the increased production of IL-6, only oxazolone and DNCB stimulated expression of TNF-alpha. The failure of BZC to initiate TNF-alpha production in the skin was not attributable to inhibition of the bioassay used to measure this cytokine and was apparently independent of the stimulation by this chemical of TNF-alpha inhibitory factors. CONCLUSION: These data indicate that not all chemicals that have the ability to cause skin irritation and cutaneous inflammation will elicit detectable TNF-alpha responses and that characterization of cutaneous irritants and allergens on the basis of induced cytokine expression patterns in the skin must be approached with caution.

Adjuvants, Immunologic↗