Search PubMed⌕ Search

Biomedical subjects

I Kimber

Publications and source records attributed to I Kimber.

At least 145 records · Page 8Linked to original sources
PubMed1996

Stimulation by oxazolone of increased IL-6, but not IL-10, in the skin of mice.

Interleukin 6 (IL-6), a multi-functional cytokine, is expressed constitutively by epidermal Langerhans cells and can be produced also by keratinocytes following stimulation. We have investigated the production of cutaneous IL-6 following topical exposure of mice to oxazolone, a potent contact allergen. Homogenates of ear skin prepared from untreated BALB/c strain mice, or from mice exposed on the dorsum of both ears to vehicle alone, contained low levels of IL-6. Topical application of oxazolone to the ears of mice induced a rapid and dose-dependent increase in IL-6 expression that was maximal 4-8 h following application and remained elevated for up to 24 h. Under the same conditions of exposure the expression of a second epidermal cytokine, interleukin 10, a product of keratinocytes, was unaffected. It is concluded that topical exposure to the chemical allergen oxazolone results in the selective stimulation of cutaneous cytokine production. The experimental approach described herein provides a simple and reliable method for the investigation of induced changes in the expression of skin cytokines.

Administration, Topical↗
PubMed1996

Workshop overview. Identification of respiratory allergens.

A variety of chemicals and proteins can sensitize the respiratory tract. Among these are materials of industrial importance, including certain diisocyanates, acid anhydrides, reactive dyes, and enzymes. Currently, no widely accepted or well-validated methods for the prospective identification of respiratory allergens exist. Most progress has been made with guinea pig methods where sensitizing potential is measured usually by assessment of changes in pulmonary function induced following sensitization and challenge. However, these methods are often prohibitively expensive, particularly for screening purposes. A number of alternative approaches are under consideration and are described here. The nature of the health problems associated with occupational respiratory sensitization, chemical structure-activity analyses as a tool for detecting pulmonary allergens, approaches used to test for respiratory allergens in guinea pigs, and alternative approaches using mice are all discussed. Finally, regulatory issues and needs with respect to respiratory sensitization are outlined.

Allergens↗
PubMed1996

Influence of dibutyl phthalate on dermal sensitization to fluorescein isothiocyanate.

What limited evidence there is indicates that the formulation in which a chemical allergen is encountered on the skin can have a marked impact upon the induction of cutaneous immune responses and the subsequent development of contact sensitization. The purpose of the present investigations was to examine further this phenomenon by analysis of the influence of dibutyl phthalate (DBP) on dermal sensitization to fluorescein isothiocyanate (FITC), a skin sensitizing fluorochrome. Addition of DBP augmented very substantially, in a dose-dependent fashion, the ability of topically applied FITC to stimulate proliferative responses in mice by draining lymph node cells (LNC), a correlate of skin sensitizing potential. Under these conditions, exposure of mice to DBP alone failed to elicit significant LNC responses. The influence of DBP on the accumulation of dendritic cells (DC) induced by FITC was examined also. Although 10% DBP had little effect on the numbers of DC found within draining nodes 18 hr following exposure of mice to FITC, the phthalate did result in a very substantial increase in the frequency of lymph node DC bearing detectable antigen (FITC+ DC). Furthermore, in the presence of DBP the median amount of FITC associated with antigen-bearing DC was higher. In vitro skin absorption studies indicated that DBP was associated with a small increase in percutaneous absorption of FITC. Collectively these data demonstrate that the vehicle formulation can exert a marked influence on dermal sensitization and that one mechanism which may be relevant is the increased acquisition of antigen by DC, associated possibly with altered penetration of the allergen into or through the skin.

Administration, Topical↗
PubMed1996

Characterization of chemical allergens as a function of divergent cytokine secretion profiles induced in mice.

Allergic contact dermatitis (contact sensitivity) may be caused by a wide variety of chemicals. In addition, some chemical allergens may also induce respiratory sensitization. It has been demonstrated previously that topical exposure of mice to chemical contact and respiratory sensitizers stimulates divergent immune responses consistent with the selective activation of T helper 1 (Th1)- and Th2-type cells, respectively. Thus, exposure to trimellitic: anhydride (TMA) induces hapten-specific IgE antibody and a substantial increase in the total serum concentration of IgE. Conversely, oxazolone fails to provoke IgE production. In addition, lymph node cells (LNC) isolated following repeated topical exposure of mice to oxazolone or TMA display cytokine secretion profiles characteristic of Th1- and Th2-type cell stimulation. The purpose of the present investigations was to determine whether chemical allergens other than TMA and oxazolone, the respiratory allergen toluene diisocyanate (TDI) and the skin sensitizer dinitrofluorobenzene (DNFB), provoke differential cytokine expression. The production of the Th1-type product interferon gamma (IFN-gamma) and the Th2-type cytokines interleukins 4 and 10 (IL-4 and IL-10) by TDI- and DNFB-activated LNC has been measured. LNC derived from DNFB-exposed animals expressed substantial amounts of IFN-gamma, but only low levels of IL-10 and mitogen-inducible IL-4; exposure to TDI resulted in the converse profile of cytokine secretion. These data demonstrate that repeated topical administration of chemical allergen of different classes elicits in mice divergent cytokine secretion patterns consistent with the selective stimulation of distinct Th subsets. Analysis of such cytokine production profiles may permit in a single integrated assay the simultaneous identification and classification of chemical allergens.

Allergens↗
PubMed1996

Adhesion molecule expression by epidermal Langerhans cells and lymph node dendritic cells: a comparison.

The migration of epidermal Langerhans cells (LC) and their transport of antigen from the skin to draining lymph nodes are of considerable importance in the induction of cutaneous immune responses, including contact sensitization. While in transit to the lymph nodes, LC are subject to a number of phenotypic changes required for their movement from the skin and acquisition of the capacity for antigen presentation. Among these are alterations in the expression of adhesion molecules that regulate interactions with the surrounding tissue matrix and with T lymphocytes. In the study described here, we investigated, using a combination of immunocytochemistry and flow cytometry, the expression by LC, and the lymph node dendritic cells into which they mature, of the three adhesion molecules, E-cadherin, intercellular adhesion molecule-1 (ICAM-1) and the membrane glycoprotein CD44. The migration of LC was associated with a marked reduction in the expression of E-cadherin, but a parallel upregulation of ICAM-1. No change in the expression of CD44 was detectable. The significance of these changes and their relevance for the functional maturation of LC are discussed.

Animals↗
PubMed1996

The role of dendritic cells in cutaneous immunity.

This article reviews the role of dendritic cells in cutaneous immunity. Langerhans cells (LC) found in the epidermis are the best-characterized dendritic cell population. They have the ability to process antigen in the periphery, transport it to the draining lymph nodes (DLN) where they are able to cluster with, and activate, antigen-specific naive T cells. During migration LC undergo phenotypic and functional changes which enable them to perform this function. There are other less well-characterized dendritic cells including dendritic epidermal T cells, dermal dendrocytes and dermal "LC-like' cells. Although there is no evidence that dendritic epidermal T cells (DETC) can present antigen or migrate to lymph nodes, they do influence the intensity of cutaneous immune responses to chemical haptens. Antigen-presenting cells (APC) in the dermis may provide alternative routes of antigen presentation which could be important in the regulation of skin immune responses. Therefore, dendritic cells are vital for the induction of immune responses to antigens encountered via the skin. LC are particularly important in primary immune responses due to their ability to activate naive T cells. The faster kinetics of secondary responses, and the ability of nonprofessional APC to induce effector function in previously activated cells, suggest that antigen presentation in the DLN may be less important in responses to previously encountered antigens. In these secondary responses, dendritic and nondendritic APC in the skin may directly induce effector functions from antigen-specific recirculating cells.

Animals↗
PubMed1996

Accessory cell requirements for T lymphocyte activation and interferon-gamma production in peripheral lymph nodes.

Allergen-activated draining lymph node cells (LNC) isolated from mice exposed topically to the contact allergen oxazolone mount vigorous proliferative responses and secrete substantial amounts of interferon-gamma (IFN-gamma) when cultured with the T lymphocyte mitogen concanavalin A (con A). In contrast, although naive LNC prepared from untreated mice display con A-driven proliferative responses of comparable magnitude, they produce only very low levels of IFN-gamma. Secretion of IFN-gamma by con A-stimulated naive LNC was augmented significantly by the addition to culture of a small number of syngeneic dendritic cells (DC), under conditions where there was no influence on the vigour of proliferative responses and where the exogenous DC themselves failed to produce IFN-gamma. Augmentation of IFN-gamma production was not observed when exogenous populations depleted of DC were added to culture. It is proposed that discrete aspects of the primary activation of naive T lymphocytes display differential requirements for accessory cells and that the development of IFN-gamma producing cells necessitates sufficient numbers of dendritic cells.

Animals↗
PubMed1996

Antigen-induced unresponsiveness in contact sensitivity: association of depressed T lymphocyte proliferative responses with decreased interleukin 6 secretion.

Topical exposure of mice to the contact allergen oxazolone induces both 4 persistent antigen-specific down-regulation of subsequent lymph node cell (LNC) proliferative responses stimulated by the same chemical and a more transient depression of LNC proliferative responses provoked by exposure to unrelated chemical sensitizers: the latter being associated with antigenic competition in contact sensitivity. In this paper a relationship between reduced LNC proliferative activity and the secretion of interleukin 6 (IL-6) is described. Pretreatment of mice with oxazolone caused a persistent, dose-dependent inhibition of LNC proliferative activity and a parallel reduction of IL-6 secretion when mice were re-exposed, at a different site, to the same chemical. Consistent with dendritic cells (DC) being the major source of IL-6 within allergen-activated lymph nodes, depletion of Thy-lt T lymphocytes did not compromise production of this cytokine. Although in mice pretreated with oxazolone IL-6 secretion by cultured LNC was impaired markedly, the initial IL-6 content of freshly isolated LNC was apparently normal. These data suggest that the down-regulation of lymphocyte proliferative responses induced by exposure of mice to oxazolone, and the consequential impaired responsiveness, is associated with, and possibly secondary to, the reduced secretion by lymph node DC of IL-6, a cytokine that is a costimulator of T lymphocyte activation and the production of which correlates closely with the vigour of LNC proliferative activity.

Adjuvants, Immunologic↗
PubMed1996

Experimental assessment of the sensitizing properties of formaldehyde.

Formaldehyde causes upper respiratory tract irritation and has been reported in some investigations to be a cause of occupational allergic asthma. The data are equivocal, however, and it has proved difficult to confirm that exposure to formaldehyde induces respiratory sensitization or provokes the production of specific immunoglobulin E (IgE) antibody. In this study the sensitizing properties of formaldehyde were examined experimentally. This chemical elicited strong positive responses in three independent methods for the prospective identification of contact sensitizing chemicals-the guinea pig maximization test, the occluded patch test of Buehler and the murine local lymph node assay. In contrast, in a novel predictive test method for assessment of respiratory sensitization potential-the mouse IgE test-formaldehyde at the same test concentrations was negative. Furthermore, formaldehyde induced in mice a pattern of cytokine secretion by draining lymph node cells inconsistent with the stimulation of IgE antibody responses or respiratory sensitization. These data indicate that, although formaldehyde is a potent contact allergen, it lacks a significant potential to cause sensitization of the respiratory tract.

Administration, Topical↗
PubMed1996

The role of the skin in the development of chemical respiratory hypersensitivity.

Certain chemicals are known to cause occupational respiratory allergy associated with symptoms of pulmonary distress, including asthma and rhinitis. While there is no doubt that inhalation represents an important route of exposure for the development of sensitization to the inducing allergen, there is evidence that effective sensitization of the respiratory tract may result also from dermal contact with the chemical. The mechanisms relevant to the stimulation of respiratory sensitization following cutaneous exposure to chemical allergens and implications for the prevention of occupational asthma are considered here.

Administration, Cutaneous↗
PubMed1996

Predictive testing for respiratory sensitization in the mouse.

Attempts to develop predictive test methods for the identification of chemical respiratory allergens have to date focused almost exclusively on the guinea pig. In recent years there has, however, been a growing interest in the mouse as a model for examination of sensitization potential. In this article two alternative approaches to the toxicological investigation of respiratory sensitization are described. Both are based on an understanding of the nature of immune responses induced in mice by chemical allergens. The mouse IgE test seeks to identify chemicals capable of causing allergic sensitization of the respiratory tract as a function of induced increases in the serum concentration of IgE. The second approach, cytokine fingerprinting, makes use of the observation that chemical allergens of different types provoke in mice qualitatively divergent immune responses characterized by discrete cytokine secretion profiles.

Allergens↗
PubMed1996

The local lymph node assay: a viable alternative to currently accepted skin sensitization tests.

The prospective identification of skin sensitizing chemicals is a vital prerequisite for their proper risk management. Traditionally this has been achieved largely by the conduct of guinea pig assays such as the maximization and Buehler tests. These methods are recommended by the Organisation for Economic Cooperation and Development (OECD) and are required by the European Union (EU) for the evaluation of new substances. However, a novel mechanistically based method, the local lymph node assay (LLNA), has been the focus of substantial validation activity in recent years. This material is reviewed in this paper. It is shown that the LLNA has been validated successfully by five interlaboratory assessments as well as by comparisons with guinea pig tests and human data. The method also offers clear advantages to the user in terms of objectivity, time and cost, and delivers important animal welfare benefits. In consequence, it is recommended that the LLNA be formally adopted by the OECD in Guideline 406 and accepted by the EU and US EPA as a method suitable for the classification of the skin sensitizing potential of chemicals.

Allergens↗
PubMed1996

Constitutive and inducible expression of interleukin-6 by Langerhans cells and lymph node dendritic cells.

During the induction phase of contact sensitization and other cutaneous immune responses a proportion of epidermal Langerhans cells (LC) is induced to leave the skin and migrate via afferent lymphatics to lymph nodes draining the site of exposure. The cells that accumulate in draining nodes have acquired the characteristics of immunostimulatory dendritic cells and effectively present antigen to responsive T lymphocytes. In the present study we have questioned whether LC in the epidermis and the lymph node dendritic cells into which they develop express interleukin-6 (IL-6), a cytokine that has been shown to serve as an important costimulator of T lymphocyte activation. In situ immunocytochemical analyses using a biotin-streptavidin staining technique revealed that dendritic cells resident in the epidermis of untreated mice constitutively express this cytokine. Keratinocytes expressed detectable IL-6 only following local exposure to the contact allergen oxazolone. Such treatment also appeared to enhance the expression by epidermal dendritic cells of this cytokine. Analyses of unfractionated and LC-enriched and -depleted populations of epidermal cells revealed a close correlation between major histocompatibility complex (MHC) class II (Ia) antigen expression and staining for IL-6, implicating LC as the sole or major source of this cytokine in unstimulated epidermis. Finally, compared with tissue isolated from mice treated with vehicle alone, draining lymph nodes prepared from animals 18 hr following sensitization with oxazolone displayed a substantial increase in both the frequency of dendritic cells and the number of IL-6+ cells within the paracortex. These data demonstrate that resident epidermal LC and the dendritic cells into which they develop are important sources of IL-6. Their constitutive and inducible expression of this cytokine will facilitate the induction of cutaneous immune responses.

Animals↗
PubMed1996

Comparison between the phenotype and function of maturing dendritic cells from spleen and lymph nodes.

We compared the capacity of mature dendritic cells (DC) from lymph nodes and maturing DC from spleens in their capacity to stimulate responses to the small hapten picryl sulphonic acid (PIC) and to the same hapten conjugated to ovalbumin (PIC-OVA) and requiring processing. Surface expression of major histocompatibility complex (MHC) class II molecules, which are upregulated during maturation of splenic DC, were studied as an independent marker of maturation. Freshly isolated lymph node DC had a veiled appearance and high levels of class II expression. DC separated from suspensions of spleen cells expressed the DC-specific marker NLDC-145, but were small, had low levels of MHC class II molecules and expressed stem cell antigen. Those DC from spleen cells cultured for 24 and 48 hr showed the development of typical veiled DC morphology and high class II expression. Lymph node DC stimulated high levels of primary T-cell proliferation to PIC, but failed to stimulate primary responses to PIC-OVA. Splenic DC isolated immediately failed to stimulate primary responses to either antigen. More mature spleen DC stimulated responses both to PIC and PIC-OVA. Surprisingly, development of the capacity to stimulate responses to PIC preceded that of stimulating PIC-OVA responses. The capacity of the DC to process and present PIC-OVA was maintained during the culture period. The results indicate that both the form of the antigen and the source and maturity of the DC are critical in determining the responses stimulated in T lymphocytes.

Animals↗
PubMed1996

Contribution of CD4+ and CD8+ T lymphocyte subsets to the cytokine secretion patterns induced in mice during sensitization to contact and respiratory chemical allergens.

Chemical allergens of different types, those that cause in humans allergic contact dermatitis or occupational asthma induce in mice divergent immune responses characteristic, respectively, of T-helper 1 (Th1)- and Th2-type cell activation. Such responses are associated with the development of different cytokine secretion patterns by draining lymph node cells (LNC), such that contact allergens stimulate vigorous interferon-gamma (IFN-gamma) production, but little secretion of the Th2 cytokines interleukin-4 and interleukin-10 (IL-4 and IL-10), whereas the converse pattern is provoked by respiratory allergens. Using selective depletion with antibody and complement we have here examined the relative contribution of CD4+ and CD8+ T lymphocytes to the cytokine secretion patterns of draining LNC isolated from mice sensitized to chemical allergens. Mice received repeated topical applications of respiratory allergens, trimellitic anhydride (TMA) or diphenylmethane diisocyanate (MDI), or of contact allergens 2,4-dinitrochlorobenzene (DNCB) or formaldehyde. Thirteen days following the initiation of exposure the production by draining LNC of IL-10, IFN-gamma and mitogen (concanavalin A)-inducible IL-4 was measured by enzyme-linked immunosorbent assay (ELISA) after various periods of culture. It was found that the high levels of IL-4 and IL-10 secretion stimulated by TMA or MDI, and the lower levels of these cytokines induced by DNCB or formaldehyde, were in all cases dependent upon the presence of CD4- cells. In contrast, the comparatively high concentrations of IFN-gamma observed following exposure to contact allergens were found to be derived from CD4+ cells, and in the case of DNCB from CD8+ cells also. The low levels of IFN-gamma induced by treatment with TMA or MDI were associated largely or wholly with CD8+ cells. These data indicate that the type 2 cytokine responses induced to different extents by both contact and respiratory chemical allergens are almost exclusively a function of CD4+ cells, but that IFN-gamma is produced by either CD4+ cells in the case of contact allergens or largely by CD8+ cells in the case of chemical respiratory allergens.

Allergens↗
PubMed1996

Dichloronitrobenzene: a reappraisal of its skin sensitization potential.

Unlike the closely related chemical dinitrochlorobenzene (DNCB), which is a very strong contact allergen, dichloronitrobenzene (DCNB) has been widely regarded as a non-allergen and, as such, a useful control for its strongly sensitizing counterpart. Nevertheless, it is still an organic chemical species readily capable of penetrating skin and, rather than being regarded as completely inert, it has even been suggested to react with the immune system in such a way that it induces specific tolerance to its chemical structure. We investigated whether DCNB was in reality a non-allergen, or rather merely a weak contact sensitizer. In both a rigorously conducted guinea pig maximization test and in a modified murine local lymph node assay, DCNB was demonstrated to possess weak sensitizing activity. On this basis, DCNB cannot be regarded as inert with respect to contact allergic potential, and is therefore inappropriate as a negative control in studies of skin sensitization.

Animals↗