Biomedical subjects

I Kimber

Publications and source records attributed to I Kimber.

At least 235 records · Page 13Linked to original sources

PubMed1991

Antigen-bearing dendritic cells in the draining lymph nodes of contact sensitized mice: cluster formation with lymphocytes.

Following topical exposure to skin-sensitizing chemicals, Langerhans' cells, a significant proportion of which bear antigen, are induced to migrate from the epidermis to the regional lymph node. There is evidence that the antigen-bearing cells which arrive in the draining lymph nodes have the functional characteristics of mature dendritic cells (DC) and efficiently induce T-lymphocyte activation in vitro and contact sensitization in vivo. In contrast, freshly isolated Langerhans' cells are known to be relatively inefficient antigen-presenting cells. Evidence exists that during culture in the presence of granulocyte/macrophage colony-stimulating factor, Langerhans' cells undergo a functional maturation and assume the characteristics of dendritic cells. We have speculated that, in response to chemical exposure and the stimulus to migrate. Langerhans' cells undergo a similar maturation in vivo. To investigate this we have examined the capacity of draining lymph node DC to form antigen-independent clusters with T lymphocytes. Previous studies have confirmed that freshly isolated Langerhans' cells are unable to form such clusters. We report, however, that the antigen-bearing DC which arrive in the draining lymph nodes following skin sensitization, and which are recently derived from epidermal Langerhans' cells, efficiently form clusters with lymphocytes. Thus, antigen-bearing DC were found to have formed clusters with lymphocytes in situ in the draining lymph node, and to readily form clusters with lymphocytes in vitro. In both cases a higher proportion of lymphocytes associated with DC in clusters were T cells. An interesting observation was that DC within draining nodes appeared more efficient at cluster formation than DC in resting nodes, and that within draining nodes antigen-bearing DC formed clusters with greater affinity and/or greater stability than DC which lacked antigen. Taken together these data demonstrate that Langerhans' cell-derived antigen-bearing cells which accumulate in the draining lymph nodes following skin sensitization form clusters with lymphocytes in the manner of mature DC. This is compatible with the hypothesis that, while in transit from the skin, Langerhans' cells are subject to a functional maturation comparable to that witnessed in vitro.

Animals↗

PubMed1991

Differential stimulation of immune function by respiratory and contact chemical allergens.

The nature of immune responses induced following topical exposure to 2,4-dinitrochlorobenzene (DNCB), a potent contact allergen which lacks the capacity to cause respiratory sensitization, and trimellitic anhydride (TMA), a respiratory allergen with comparatively weak skin-sensitizing potential, have been investigated. Exposure of BALB/c strain mice to concentrations of TMA and DNCB which resulted in equivalent levels of activation (cell proliferation) in lymph nodes draining the site of application (50% TMA and 1% DNCB) induced comparable levels of contact sensitization and IgG anti-hapten antibody production. However, under these conditions, exposure only to TMA resulted in an elevation of serum IgE. Furthermore, while TMA induced IgG2b rather than IgG2a antibody the reverse pattern was observed with DNCB. These data demonstrate that TMA and DNCB elicit qualitatively different immune responses which are consistent with their potential to cause respiratory and contact allergy, respectively. The possibility that the responses induced by these chemicals reflect a differential stimulation of T-helper cell subsets (Th1 and Th2) is discussed.

Allergens↗

PubMed1990

Identification of contact allergens using the murine local lymph node assay: comparisons with the Buehler occluded patch test in guinea pigs.

A murine local lymph node assay has been developed for the identification of contact sensitizing chemicals. In the present study, the performance of the local lymph node assay has been evaluated with twenty-four coded chemicals of previously unknown skin sensitizing potential and the results compared with predictions made from concurrent occluded patch tests (Buehler tests) in guinea pigs. The data presented demonstrate that the local lymph node assay successfully identified those chemicals that were classified as moderate or strong skin sensitizers in the Buehler test. In the present series of experiments, chemicals predicted to be mild sensitizers in the Buehler test were classified as 'not strong sensitizers' in the local lymph node assay. In the majority of instances, the Buehler test and local lymph node assay were in agreement with regard to the identification of non-sensitizing chemicals. However, two chemicals that were classified as non-sensitizers in the guinea pig test exhibited positive responses in the local lymph node assay and were predicted to be sensitizers. Some coloured chemicals resulted in obscured Buehler readings and, here, assessment was based upon histological examination of the challenge site. These compounds were examined also in the local lymph node assay and similar predictions of sensitizing potential were made. Taken together, the data reveal close, but not absolute, concordance between the local lymph node assay and the Buehler test. The relative merits of these predictive test methods are discussed.

Allergens↗

PubMed1990

1-Chloromethylpyrene: a reference skin sensitizer and genotoxin.

1-Chloromethylpyrene (1-CMP) has been evaluated as a model mutagen and toxin related to the ultimate electrophiles derived from benzo[a]pyrene and 1-nitropyrene. It was mutagenic to Salmonella (greater than 100 pg/plate) and exceptionally reactive to DNA when assessed by the 32P-postlabelling technique. 1-CMP was inactive in a mouse bone micronucleus assay when administered by gavage, probably due to hydrolysis, whose kinetics have been studied (t1/2 approximately 23 min at 37 degrees C). However, as expected, it was a potent skin toxin as determined by its activity as a mitogen to mouse skin and its contact allergenicity, as determined using the local lymph node proliferative assay. It is concluded that 1-CMP will probably be a potent human skin carcinogen and contact allergen.

Animals↗

PubMed1990

Contact sensitization of mice to nickel sulphate and potassium dichromate.

The ability of nickel sulphate and potassium dichromate to induce contact sensitization in mice has been investigated. Topical exposure of mice to 0.5% potassium dichromate in dimethylsulphoxide (DMSO) under occlusion resulted in specific contact sensitization in each of 7 experiments. Although sensitization to nickel sulphate under the same conditions was weak and somewhat variable, evidence for significant levels of contact allergy was obtained in 4 of 7 experiments. In addition, repeated topical application of both nickel sulphate and potassium dichromate in DMSO was found to result in the induction of lymphocyte proliferative responses in lymph nodes draining the site of exposure. These data indicate that epicutaneous exposure to both metal salts may cause specific contact sensitization in mice.

Animals↗

PubMed1990

Antigen-restricted antigenic competition induced by 2,4-dinitrochlorobenzene: association with depression of lymphocyte proliferation.

2,4,6-Trinitrochlorobenzene (picryl chloride) and 2,4-dinitrochlorobenzene (DNCB) fail to cross-sensitize with respect to contact sensitivity in mice. Nevertheless, topical exposure of mice to DNCB and other skin-sensitizing dinitrobenzene derivatives was found to result in a significant impairment of draining lymph node cell proliferative responses induced following epicutaneous challenge with picryl chloride 5 days later. The inhibition of picryl chloride induced proliferation was associated with an impairment of contact sensitization to this chemical. The effect of DNCB on subsequent responses to picryl chloride was transient and no longer detectable 15 days following exposure. The inhibition of proliferation and contact sensitization caused by DNCB was largely restricted to picryl chloride. Thus, DNCB failed to influence the development of contact allergy to the unrelated chemical 4-ethoxymethylene-2-phenyloxazol-5-one (oxazolone) and exerted a far less pronounced effect on oxazolone-induced proliferative responses. These data, therefore, describe an antigen-restricted form of antigenic competition which is associated with a depression of the primary lymphocyte proliferative response.

Animals↗

PubMed1990

Contact hypersensitivity induces plasma interleukin 6.

Previous studies in this laboratory have revealed that elicitation reactions in contact-sensitized mice correlate closely with elevations in the serum concentration of acute-phase proteins. Regulation of the hepatic synthesis of acute-phase proteins is one of the many biological functions ascribed to interleukin 6 (IL-6). We now provide evidence that contact reactions are also associated with a rapid and substantial increase in the plasma concentration of IL-6. Quantitative assessment of plasma IL-6 may provide a useful serological method for the evaluation of experimental allergic contact dermatitis in mice, and possibly in other species.

Animals↗

PubMed1990

Correlation between lymphocyte proliferative responses and dendritic cell migration in regional lymph nodes following skin painting with contact-sensitizing agents.

We have investigated whether there exists a correlation between the induction of draining lymph node cell (LNC) proliferation in contact allergy and the accumulation of dendritic cells (DC) within such lymph nodes. CBA/Ca mice, which compared with mice of BALB/c strain, mount a more vigorous lymphocyte proliferative response following sensitization, also exhibited a more marked accumulation of DC in draining lymph nodes 24 h following skin painting. Moreover, studies with the skin-sensitizing fluorochromes fluorescein isothiocyanate (FITC) and rhodamine B isothiocyanate (RITC) revealed that DC-enriched fractions of draining LNC prepared from CBA/Ca mice contained a higher percentage of antigen-bearing cells than did those from BALB/c mice. A relationship between DC migration into lymph nodes and the magnitude of the induced LNC proliferative response was also indicated by experiments performed in BALB/c mice with a variety of contact allergens. It was observed that there was a direct correlation between the vigour of the proliferative response measured 3 days following exposure and the frequency of DC in draining nodes at 24 h. Collectively these data suggest that following skin sensitization the migration of DC into the draining lymph nodes influences quantitatively the primary immune response and the development of contact allergy.

Allergens↗

PubMed1990

Requirements for antigenic competition in contact sensitivity.

The requirements for the induction of antigenic competition in murine contact sensitivity have been examined. Experiments with a variety of skin-sensitizing chemicals revealed a correlation between immunogenicity and the ability to inhibit subsequent responses to an unrelated contact allergen, oxazolone. Previous studies have suggested that, in contact sensitivity at least, antigenic competition is the consequence of a reduced lymphocyte proliferative response to the second antigen. We investigated whether the regulatory events which impair proliferation following exposure to the second antigen are induced as the result of a strong proliferative response to the first (competitor) antigen. It was found, however, that significant inhibition of the primary proliferative response to picryl chloride, by pretreatment of mice with either picryl sulphonic acid or 2,4-dinitrochlorobenzene, failed to prevent picryl chloride inducing antigenic competition for oxazolone. Our studies suggest that following topical exposure to potent skin allergens events other than proliferation in draining lymph nodes induce active immunoregulatory processes, one consequence of which is the appearance of antigenic competition.

Animals↗

PubMed1990

Phenotypic characteristics of antigen-bearing cells in the draining lymph nodes of contact sensitized mice.

Following contact sensitization of mice there is a rapid accumulation of dendritic cells (DC) within lymph nodes draining the site of exposure. Previous studies have revealed that cells bearing high levels of contact allergen can also be identified within the low buoyant density fraction of draining lymph node cells, and it has been assumed that the majority of these are DC. The purpose of the present study was to establish the phenotypic characteristics of the antigen-bearing cells which appear in lymph nodes within hours of skin painting with contact allergens, including the contact sensitizing fluorochromes fluorescein isothiocyanate (FITC) and rhodamine B isothiocyanate (RITC). Indirect immunofluorescence and two-colour immunofluorescence analyses revealed that initially all antigen-bearing cells which arrive in the draining lymph nodes express class II MHC antigens and exhibit a dendritic morphology. Phagocytic cells, cells reactive with F4/80 and anti-Mac-1 antibodies and lymphoblasts are not associated with detectable levels of antigen. In addition, although Thy-1+ cells co-fractionate with lymph node DC they are not dendritic in nature and are not associated with antigen. These data are compatible with the hypothesis that following skin sensitization epidermal Langerhans' cells bind antigen and transport it to the regional lymph nodes. In addition, it is clear that the recently described population of Thy-1+, Ia- dendritic cells within the murine epidermis do not perform a similar function.

Adenosine Triphosphatases↗

PubMed1990

Antigenic competition in contact sensitivity. Evidence for changes in dendritic cell migration and antigen handling.

The frequency and antigen-bearing characteristics of dendritic cells (DC) within draining lymph nodes have been examined during antigenic competition in contact sensitivity. Pre-exposure of mice to oxazolone on the flank resulted in a marked depression of subsequent fluorescein isothiocyanate (FITC)-induced lymph node cell (LNC) proliferation. Antigenic competition was associated with an increased frequency of DC in the draining lymph nodes, but also with a reduced amount of antigen per cell. Thus, at 24 hr the draining nodes of FITC-challenged mice previously exposed to oxazolone exhibited an increased number of DC compared with control animals. Flow cytometric analysis revealed, however, that the percentage of antigen-bearing DC was reduced and that the median amount of antigen borne by DC was lower. Since exposure to oxazolone caused a significant increase in the frequency of DC in distant nodes, the changes observed in antigenic competition may, at least in part, be attributable to systemic effects on DC migration following application of the first antigen. These data indicate that the reduced primary proliferative response which characterizes antigenic competition in contact sensitivity is associated with, and may result from, induced changes in dendritic cell behaviour.

Animals↗

PubMed1990

Systemic migration of dendritic cells during contact sensitization.

Twenty-four hours after skin painting mice on the flank with the contact sensitizer fluorescein isothiocyanate (FITC), the number of dendritic cells (DC) increased sharply, not only in draining but also in contralateral (CLN) and distant lymph nodes. High levels of antigen were detected on up to 50% of DC isolated from draining lymph nodes (DLN), and these cells were potent stimulators of naive T cells in vitro. Less than 3% of DC from contralateral and distant lymph nodes carried detectable antigen and did not induce significant T-cell proliferation. A significant number of DC had migrated to draining, contralateral and distant lymph nodes without acquiring detectable antigen. This indicates that there is a systemic signal causing the movement of DC to lymph nodes. This appears to be independent of mature T cells, as the systemic migration of DC also occurred in nude mice.

Animals↗

PubMed1990

Production of interleukin-1 by draining lymph node cells during the induction phase of contact sensitization in mice.

Biologically active interleukin-1 (IL-1) has been detected in supernatants of draining lymph node cells isolated from contact-sensitized mice. Induction of IL-1 was dependent upon the concentration of sensitizer applied and occurred within 2 hr of exposure. The IL-1 activity could not be attributed to other interleukins and was neutralized by a specific antiserum. Reduced concentrations of IL-1 were produced by cells isolated from the draining nodes of mice that had been pre-exposed to the sensitizer. Since IL-1 has the potential to influence several aspects of lymphocyte activation, the production of significant concentrations of biologically active IL-1 by draining lymph node cells indicates that it is likely to play an important role in the afferent phase of contact sensitization.

Animals↗

PubMed1989

Immunotoxicology: suppressive and stimulatory effects of drugs and environmental chemicals on the immune system. A discussion.

The fundamental characteristic of the adaptive immune system which has evolved in the vertebrates is the ability to recognise, and subsequently destroy, "foreign", and potentially harmful, antigens. The selective advantage which the immune system confers is the capacity to resist infectious, and possibly malignant, disease. It has been apparent for many years that individuals in whom immune function is impaired, due either to a congenital defect or to other factors such as treatment with certain immunosuppressive drugs, exhibit an increased susceptibility to infection and, in some cases, an elevated risk of developing at least some forms of malignancy. There is an increasing awareness from rodent studies that a variety of drugs and environmental chemicals have the potential to unintentionally impair components of the immune system. Risk assessment, based upon data from chemically induced changes in one or more parameters of immune function, is, however, dependent upon a knowledge of the functional reserve of the immune system. One of the objectives of the meeting from which this report derives was to examine what sources of information are available, and what experimental protocols can be employed, to permit accurate evaluation of immunological reserve. Although, under normal circumstances, the immune system selectively and specifically recognises foreign antigen, it is clear that the potential to recognise "self" is present and that in certain circumstances this potential is realised. Antibodies directed against normal tissue antigens have been shown to be associated with, and in some instances the presumptive cause of, "autoimmune" disease. There is a growing list of drugs and chemicals which are capable of eliciting autoantibodies and pathological autoimmune reactions. A second purpose of this meeting and of this report was to review the current state of knowledge regarding drug- and chemical-induced autoimmunity.

Adjuvants, Immunologic↗

PubMed1989

A murine local lymph node assay for the identification of contact allergens. Assay development and results of an initial validation study.

The development of an alternative predictive test for the identification of contact sensitizing chemicals is described. The method is based upon the fact that, following epicutaneous application, sensitizing chemicals initiate a primary immunological response in the draining lymph node(s) which is characterized by lymphocyte proliferation. Experimental conditions for the measurement in vitro of the induced lymph node cell proliferative response have been optimized. On the basis of the data presented a local lymph node assay was developed in which CBA/Ca strain mice were exposed daily, for 3 consecutive days, to various concentrations of the test chemical, or to vehicle alone, on the dorsum of the ear. Lymph node activation was measured subsequently as a function of increased node weight, the frequency of large pyroninophilic cells and lymphocyte proliferation in the presence or absence of an exogenous source of interleukin 2 (IL-2). The results of a validation study are reported in which 22 well-characterized sensitizing chemicals of varying potency were examined. With the exception of three chemicals where water was used as the application vehicle, positive responses, defined as a substantial increase in lymphocyte proliferative activity, were recorded with all these test materials. Under the conditions employed non-sensitizing chemicals, including non-sensitizing irritant chemicals, failed to influence the immunological status of the draining lymph node. Taken together, the data suggest that the local lymph node assay provides the basis for a rapid and cost-effective alternative to the currently available guinea pig predictive test methods. The local lymph node assay may be of particular value for the evaluation of coloured or irritant chemicals.

Allergens↗

PubMed1989

Antigen-specific regulation of T lymphocyte proliferative responses to contact-sensitizing chemicals in the guinea pig.

Skin painting of guinea pigs with either 4-ethoxymethylene-2-phenyloxazol-5-one or 2,4-dinitrofluorobenzene induced not only a primary proliferative response in the draining lymph node but also the systemic suppression of subsequent proliferative responses to topically applied hapten. The inhibition of lymphocyte proliferation, as assessed by the incorporation of [3H]-thymidine and the presence of large pyroninophilic cells in the paracortex, was hapten-specific and long-lasting. This study demonstrates that, in common with the mouse, the sensitization of guinea pigs results in the induction of a hapten-specific suppressor mechanism, which serves to control the proliferative response following reexposure to hapten. However, the antigen-nonspecific suppression of proliferation observed in the mouse following exposure to some potent contact sensitizers was not, under the conditions employed, detectable in the guinea pig.

Allergens↗

PubMed1989

Aspects of the immune response to contact allergens: opportunities for the development and modification of predictive test methods.

A variety of guinea-pig tests are currently employed to assess the skin-sensitizing potential of chemicals. Although some such tests, in particular the guinea-pig maximization test and the occluded patch test of Buehler, have become well established, widely applied and are of proven value in the safety evaluation of chemicals, they have certain limitations. It is the purpose of this review to examine various aspects of the immune response to contact allergens and the way in which an understanding of the molecular and cellular events that characterize the induction and elicitation of contact sensitivity may be applied to the development and modification of predictive test methods. Attention is focused on the role of dendritic cell migration and T lymphocyte activation during the induction phase of skin allergy and the association of acute-phase proteins and vasoactive amines with the elicitation reaction.

Allergens↗

PubMed1989

The role of antibody density in the immune lysis of sensitised erythrocytes. A mathematical appreciation.

The influence of sensitizing antibody density on target cell selection by effector monocytes was examined by modifying the sensitization of red cells either by dilution of the antiserum, variation of the number of erythrocytes or both in a cold target competition assay of antibody-dependent cellular cytotoxicity (ADCC). Human A1 and B erythrocyte target and competitor cells were employed in the presence of hyperimmune anti-A and anti-B sera at concentrations above that necessary for saturation of red cells with respect to lytic susceptibility. When the number of red cells was kept constant and the dilution of antisera was varied a linear relationship between the competitive capacity of erythrocytes and the concentration of sensitizing antiserum was observed. When the number of target (competitor) cells and the concentration of antisera were varied simultaneously it was apparent that the competitive capacity was dependent upon the relative densities of the sensitizing antibodies. When competition was tested in the presence of suboptimal concentrations of complement, rather than effector cells it was observed that, in common with ADCC, the effectiveness of cold competition was dependent upon the concentration of sensitizing antibody.

ABO Blood-Group System↗