Environmental immunogens and T-cell-mediated responses in fibromyalgia: evidence for immune dysregulation and determinants of granuloma formation

Thirty-nine patients with fibromyalgia syndrome (FMS) according to American College of Rheumatology criteria were studied for cell-mediated sensitivity to environmental chemicals. Lymphocytes were tested by standard [(3)H]thymidine incorporation in vitro for T cell memory to 11 chemical substances. Concanavalin A (Con A) was used to demonstrate T cell proliferation. Controls were 25 contemporaneous healthy adults and 252 other concurrent standard controls without any aspect of FMS. Significantly higher (P < 0.01) stimulation indexes (SI) were found in FMS for aluminum, lead, and platinum; borderline higher (0.05 > P > 0.02) SI were found for cadmium and silicon. FMS patients showed sporadic responses to the specific substances tested, with no high-frequency result (>50%) and no obvious pattern. Mitogenic responses to Con A indicated some suppression of T cell functionality in FMS. Possible links between mitogenicity and immunogenic T cell proliferation, certain electrochemical specifics of granuloma formation, maintenance of connective tissue, and the fundamental nature of FMS are considered.

Contact sensitivity to nickel and other metals in jewelry reactors

BACKGROUND

Many patients who give a history of a dermatitis reaction to jewelry or metal contact with skin are negative to metals on standard patch testing. Some may be showing false-negative reactions.

OBJECTIVE

Our purpose was to determine whether patients with a history of jewelry reactions but whose standard patch tests were negative have a false-negative reaction or are allergic to metals other than nickel, cobalt, or chromium.

METHODS

Four hundred forty-nine patients were studied who gave a history of reacting to jewelry or metal. Of these, 210 were tested to the metals in the European standard series (ie, nickel, cobalt, and chromate), and 239 were tested to the metals in the standard series and to an extended metal series of palladium, gold, platinum, a second nickel salt, and a nickel/cobalt mixture. These were compared with 752 patients who did not give a history of jewelry or metal reactions, of which 50, besides the standard series, were also treated with the additional metal series.

RESULTS

A higher proportion of jewelry-reactive patients tested with the extended series reacted to nickel (and to other metals) than those who were tested only with the European standard series: (61% vs 38%; P <.0001 ). The use of the extended series showed that palladium allergy was common, present in 34% of nickel-allergic patients, but it always occurred with nickel sensitivity. Gold allergy coexisted with nickel sensitivity in 10% of cases. Testing simultaneously with separate patches containing 5% nickel sulfate and 5% nickel chloride showed a concordance of 71% in identified nickel-sensitive patients. Nickel sulfate was more likely than nickel chloride to detect nickel sensitivity. The use of a combined preparation of 2.5% nickel sulfate and 0.5% cobalt chloride in petrolatum revealed only 3 jewelry-reactive patients who were negative to other metals. There was a slightly higher proportion of atopic patients in the patch test-negative jewelry reactors group than in the positive group; however, the difference was not significant and it was not sufficient to account for the negative findings.

CONCLUSION

Some jewelry reactors who had negative patch tests are likely to be subclinically allergic to nickel. We suggest that the higher number of antigens, or perhaps the larger nickel load, in the extended metal series, resulted in a larger proportion of patients reacting. To better demonstrate nickel allergy in jewelry reactors, patients should be patch tested to a metal series that contains palladium and gold salts and perhaps a second nickel patch because these may reveal the presence of nickel sensitivity when standard patch tests would otherwise have been negative.

Hypersensitivity to metallic biomaterials: a review of leukocyte migration inhibition assays

Metal hypersensitivity is a well-established phenomenon occurring in a variety of domestic and workplace settings. Degradation products of metallic biomaterials may mediate metal hypersensitivity. However, little is known about the short- and long-term pharmacodynamics and bioavailability of circulating metal degradation products in vivo. Mechanisms by which in vivo metal sensitivity reactions occur have not been well characterized and the degree to which metal sensitivity may be a predisposing factor for eliciting an overaggressive immune response remains clinically unpredictable. In vitro leukocyte migration inhibition assays have been used for investigating cell-mediated hypersensitivity reactions to biomaterial and biomaterial degradation products. This review provides a historical and technical summary of four in vitro techniques used for determination of leukocyte migration activity: (1) membrane migration or Boyden chamber, (2) capillary tube, (3) leukocyte migration using agarose technique, and (4) collagen gels. It is difficult to determine which, if any, of these techniques is singularly best suited for the investigation of suspected biomaterial-related symptoms in patients. However, Boyden chamber membrane migration testing is recommended for clinical investigations, principally because a high degree of standardized investigator independent materials and methodologies is necessary for compiling and comparing the results of patients tested at various times over the length of an extended study. Ultimately, in vitro migration inhibition testing has the potential to provide a reliable means for predicting some complications and thus enhancing the outcome for patients receiving metallic implants. Continuing improvements in migration inhibition testing methods, used alone or in combination with other immunologic assays, will likely improve assessment of patients susceptible to biomaterial antigen-induced delayed-type hypersensitivity responses.

Exacerbation of pustulosis palmaris et plantaris after topical application of metals accompanied by elevated levels of leukotriene B4 in pustules

BACKGROUND

Pustulosis palmaris et plantaris (PPP) is a chronic inflammatory disease consisting of polymorphonuclear leukocyte infiltration, and is often exacerbated by focal infections such as tonsillitis. In some cases, metal allergy has been reported.

OBJECTIVE

The purpose of this study was to evaluate (1) the significance of metal allergy in the formation of pustules, and (2) the participation of leukotriene (LT) B(4) in the formation of pustules of PPP.

METHODS

Patch tests with metals were performed on 7 patients with PPP, and both pustular and plasma levels of LTB(4) were measured in these 7 patients before and 48 hours after metal patch tests.

RESULTS

Palmoplantar pustules were exacerbated after the metal patch tests in all 7 patients. The mean levels of LTB(4) in plasma and pustules of the volar surface at 48 hours after the metal patch tests were significantly higher than those before the metal patch tests.

CONCLUSION

Metals can be important in the pathogenesis of PPP by contributing to the induction of high LTB(4) concentration in the pustules.

Enhanced allergic sensitization by residual oil fly ash particles is mediated by soluble metal constituents

Epidemiological studies have demonstrated an association between elevated levels of particulate matter (PM) air pollutants and exacerbation of asthma symptoms. We have shown in a Brown Norway (BN) rat model of house dust mite (HDM) allergy that preexposure to residual oil fly ash (ROFA) particles enhanced the sensitization phase such that the secondary immune response and associated lung injury were increased after allergen challenge. To determine whether the metals present in ROFA mediated this effect, BN rats were intratracheally instilled with either ROFA (1000 microg) or acidified saline + NiSO(4) (105.12 microg), VSO(4) (98.2 microg), FeSO(4) (58.49 microg), or a mixture (Mix) of each metal. HDM-specific IgE was higher in the serum of the ROFA, Ni, V, and Mix groups than in the HDM group after challenge, and antigen-induced bronchoconstriction responses were increased in the Ni group. Lymphocyte proliferation to antigen was increased in the ROFA, Ni, and V groups compared to controls. Total protein and eosinophil peroxidase levels were elevated in the Fe group, and eosinophil numbers in the bronchoalveolar lavage fluid (BALF) were increased in the ROFA and Fe groups compared to HDM control. IL-5 and IL-13 mRNA expression was also increased in the lung tissue of all metal and ROFA-treated groups, while BALF IL-10 was elevated in the Fe and Mix groups, and IL-6 and TNF-alpha were elevated in the metal and ROFA-treated groups compared to controls. These results suggest that ROFA's metallic constituents mediate enhancement of sensitization to HDM and that pulmonary inflammation may play a role in this adjuvant effect.

Relevant contact sensitivities in patients with the diagnosis of oral lichen planus

BACKGROUND

The concept of contact allergy aggravating or inducing oral lichenoid mucositis diagnosed as oral lichen planus (OLP) is well recognized but somewhat controversial.

OBJECTIVE

We sought to identify clinically relevant contact allergens that may be important in the management of patients with OLP.

METHODS

We retrospectively reviewed patients with OLP who had patch tests performed at Mayo Clinic Rochester and Mayo Clinic Scottsdale from 1994 to 1997 and 1988 to 1997, respectively.

RESULTS

Patch tests were performed on 46 patients with a clinical and histopathologic diagnosis of OLP. Of these, 25 (54%) had positive patch test results. Eighteen (72%) of the patients with positive results had clinically relevant reactions. Of the patients with positive metal reactions, 5 had improvement after removal of the metal prosthesis or restoration. Six others noted that their most troublesome areas were adjacent to metal dental restorations. Six patients with reactions to flavorings and one patient with an acrylate dental retainer sensitivity had improvement after avoiding these allergens.

CONCLUSION

Our findings support the concept that contact allergy to metals, flavorings, and plastics can be important in the pathogenesis and management of patients with oral lichenoid mucositis diagnosed as OLP.

Immunologic mechanisms in hypersensitivity reactions to metal ions: an overview

Metal ions such as Ni2+, Co2+, Cu2+, or Cr3+ are haptens with a high immunogenic potential, as contact dermatitis caused by ionic metals occurs in about 10-15% of the human population. Since alloys containing Ni2+, Co2+, and Cr3+ are components of implants in replacement surgery, dentures, orthodontic wires, and various other devices, adverse reactions to metal ions create serious problems in practical medicine as incompatibility reactions to metal-containing biomaterials. On the other hand, contact dermatitis to metal ions such as Ni2+ is a well-established model for studying the molecular mechanisms involved in the recognition of haptens by the immune system. Although many investigations have been performed to elucidate the molecular interactions causing contact hypersensitivity in man, many aspects remain to be clarified. This review will focus on the experimental data accumulated so far on the immunologic mechanisms responsible for the recognition of metal ions by T cells and eliciting adverse immune reactions causing contact dermatitis.

Identification of metal allergens in the local lymph node assay

BACKGROUND

The murine local lymph node assay (LLNA) has recently been endorsed as a validated alternative to guinea pig methods for the identification of skin sensitization hazard. Nevertheless, there has been some debate regarding the utility of this method for the detection of metal contact allergens.

OBJECTIVE

In these investigations, we have used the LLNA to determine the skin sensitization potential of 13 metal salts, 8 of which were considered to possess a significant ability to sensitize man, whereas the remaining 5 were judged to lack such potential.

RESULTS

The predictions from the LLNA were correct for 7 of the 8 (88%) sensitizing metals and for 4 of the 5 (80%) nonsensitizers when considered against the experience of these metals as human skin sensitizers. Thus, the overall predictive accuracy of the LLNA in relation to metals was 11/13 (85%), which is very similar to the accuracy of approximately 88% in relation to a much larger number of low-molecular-weight organic chemicals, as reported previously.

CONCLUSION

These data provide support for the potential utility of the LLNA in hazard identification of metal contact allergens.

Nickel allergy in mice: enhanced sensitization capacity of nickel at higher oxidation states

Attempts to induce contact hypersensitivity to nickel in mice using, e.g., Ni(II)Cl2 often failed. Here, we report that sensitization was achieved by injecting Ni(II)Cl2 in combination with either CFA or an irritant, such as SDS and PMA, or IL-12, or by administering nickel at higher oxidation states, i.e., Ni(III) and Ni(IV). Although Ni(II), given alone, was ineffective in T cell priming, it sufficed for eliciting recall responses in vivo and in vitro, suggesting that Ni(II) is able to provide an effective signal 1 for T cell activation, but is unable to provide an adequate signal 2 for priming. Immunization of mice with nickel-binding proteins pretreated with Ni(IV), but not with Ni(II), allowed them to generate nickel-specific CD4+ T cell hybridomas. Ni(II) sufficed for restimulation of T cell hybridomas; in this and other aspects as well, the hybridomas resembled the nickel-specific human T cell clones reported in the literature. Interestingly, restimulation of hybridomas did not require the original Ni(IV)-protein complex used for priming, suggesting either that the nickel ions underwent ligand exchange toward unknown self proteins or peptides or that nickel recognition by the TCR is carrier-independent. In conclusion, we found that Ni(III) and Ni(IV), but not Ni(II) alone, were able to sensitize naive T cells. Since both Ni(III) and Ni(IV) can be generated from Ni(II) by reactive oxygen species, released during inflammation, our findings might explain why in humans nickel contact dermatitis develops much more readily in irritated than in normal skin.

Evaluation of a colloidal metal immunoassay device for the detection of tricyclic antidepressants in urine

BACKGROUND

The sensitivity and selectivity of a colloidal metal immunoassay device (Triage Plus TCA) which is designed for the rapid detection of tricyclic antidepressant drugs in urine at a total tricyclic antidepressant concentration of 1000 ng/mL or greater were evaluated.

METHODS

The sensitivity of the Triage Plus assay was determined by adding known amounts of amitriptyline, nortriptyline, imipramine, desipramine, doxepin and desmethyl-doxepin to drug free urine. The selectivity of the assay was determined by adding known concentrations of 32 drugs or drug metabolites commonly encountered in emergency department admissions to drug free urine. Triage Plus results from clinical urine specimens containing either amitriptyline, nortriptyline, imipramine, desipramine, doxepin and desmethyl-doxepin were compared to those obtained with thin layer chromatography and high performance liquid chromatography.

RESULTS

Triage Plus yielded a positive response to gravimetrically prepared urines of tricyclic antidepressant at the stated cut-off value (1,000 ng/mL), and at 80% (800 ng/mL) and 50% (500 ng/mL) of the cut-off with amitriptyline, nortriptyline, imipramine, desipramine and doxepin. Other tricyclic antidepressant drugs, clomipramine and protriptyline were positive at 1000 ng/mL. Significant cross-reactivity was observed only with cyclobenzaprine at 1000 ng/mL. No significant cross reactivity was found at 1.0 g/L for 32 drugs commonly encountered in emergency department admissions. A 95% (70/74) agreement of positive tricyclic antidepressant results was observed between Triage Plus and thin layer chromatography. Discordant urines were found by high performance liquid chromatography to contain tricyclic antidepressant concentrations below the cut-off value of the colloidal metal assay.

CONCLUSION

Triage Plus was found to be an accurate device for the detection of tricyclic antidepressants in urine at the stated cut-off value of 1000 ng/mL tricyclic antidepressant. With the exception of cyclobenzaprine, significant cross-reactivity was not observed with other drugs commonly encountered in emergency department admissions.

Human monocyte/macrophage response to cobalt-chromium corrosion products and titanium particles in patients with total joint replacements

The responses of human peripheral blood monocytes of 10 normal volunteers and 14 patients with total hip replacements to particles of commercially pure titanium and chromium orthophosphate (a corrosion product from cobalt-chromium alloy implants) were studied. In addition, these phagocytosable particles were added to cultured mononuclear cells isolated from the interfacial membrane of 14 patients with failed implants. Peripheral blood monocytes from patients who had had a total hip replacement produced significantly higher levels of interleukin-1 (both interleukin-1 alpha and interleukin-1 beta) and prostaglandin E2 following particulate stimulation than those from normal volunteers. Supernatants from both titanium and chromium orthophosphate-stimulated peripheral blood monocytes from the volunteers and patients with total hip replacement induced bone resorption (assayed in organ cultures of newborn mouse calvariae) and the proliferation of human fibroblasts. The levels of bone resorption were significantly higher (p < 0.05) in patients with implants than in normal volunteers. There were no significant differences in the responses of cells between patients with focal osteolysis and those without osteolysis. Interfacial membrane mononuclear cells also produced high levels of interleukin-1 alpha, interleukin-1 beta, and prostaglandin E2 and expressed bone resorptive activities following stimulation with either titanium or chromium orthophosphate. More importantly, interfacial membrane mononuclear cells "spontaneously" produced high levels of prostaglandin E2 that were comparable with the response of peripheral blood monocytes stimulated with particulate wear debris. The clinical relevance of this study is 2-fold. First, mononuclear cells from patients with total hip replacement were some-how "sensitized" to metal particles in comparison with mononuclear cells from individuals without an implant. Second, the chromium orthophosphate corrosion product was a potent macrophage/monocyte activator and may contribute to macrophage-mediated osteolysis and aseptic loosening.

Metal binding properties of a monoclonal antibody directed toward metal-chelate complexes

A monoclonal antibody that recognizes cadmium-EDTA complexes has been produced by the injection of BALB/c mice with a metal-chelate complex covalently coupled to a carrier protein. The ability of purified antibody to recognize 16 different metal-EDTA complexes was assessed by measuring equilibrium binding constants using a KinExATM immunoassay instrument. The antibody bound to cadmium- and mercury-EDTA complexes with equilibrium dissociation constants of 21 and 26 nM, respectively. All other metal-EDTA complexes tested, including those of Mn(II), In(III), Ni(II), Zn(II), Co(II), Cu(II), Ag(I), Fe(III), Pb(II), Au(III), Tb(III), Ga(III), Mg(II), and Al(III) bound with affinities from 20- to 40,000-fold less than that determined for the cadmium-EDTA complex. With the exception of mercury and magnesium, the binding of divalent metal-chelate complexes was well-correlated with the size of the metal ion. The amino acid sequences of the heavy and light chain variable regions were deduced from polymerase chain reaction-amplified regions of the corresponding genes and subsequently used to construct molecular models of the antigen binding region. The key residue for cadmium binding in the model for 2A81G5 appeared to be histidine 96 in the heavy chain.

Multiple sensitivities to transition metals: the nickel palladium reactions

Patch test data of 1000 consecutive patients sensitive to at least 1 substance of our standard series showed that transition metals gave associated reactions amongst themselves more frequently than they did with the remaining substances. The responses to transition metals were largely variable and seemed dependent not only upon the associated exposure to different metals or the concomitant responses of the T cell clones, as reported by others, but also upon the chemical properties of the metals and the consequent interactions inside the skin. Concomitant reactions to nickel sulfate and palladium chloride were the most frequently found associated positivities and occurred in a minority of nickel-sulfate-sensitive subjects. In 43 out of 45 of these subjects, patch tests to mixed solutions containing nickel sulfate, plus sulfates of magnesium, zinc, and manganese at higher doses, were not able to reduce the nickel sulfate reactions. This behaviour contrasted with that found in the majority of subjects sensitive only to nickel sulfate. These findings seem to demonstrate that, whilst in subjects with positive reactions to nickel sulfate alone antigen formation involves biomolecules containing ions, in those with concomitant reactions to palladium chloride, other structures are involved.

Using antibodies to perturb the coordination sphere of a transition metal complex

Metal ions in the active sites of many metalloenzymes exhibit distinctive spectral and chemical features which are different from those of small inorganic complexes. These features are the result of the unusual geometric and electronic constraints that are imposed on the metal ion within the protein environment. Much effort has been invested to try to mimic this feature of metalloenzymes in synthetic systems, but this remains a formidable task. Here we show that one of the key lessons learned from the science of catalytic antibodies--that binding energy can be converted into chemical energy--can be exploited to 'fine-tune' the physicochemical properties of a metal complex. We show that an antibody's binding site can reversibly perturb the coordination geometry of a metal ion, and can stabilize a high-energy coordinated species. Specifically, antibodies designed to bind the organosilicon compound 1 also bind the geometrically similar Cu(I) complex 2. However, the antibody binds a slightly compressed form of 2, which is closer in size to 1. This distortion is manifested by a spectral shift--an 'immunochromic' effect.

Metal-binding properties of a calcium-dependent monoclonal antibody

The calcium-dependent mAb, M1 (also called anti-Flag or 4E11) was studied using a newly developed metal-sensitive enzyme-linked immunosorbent assay (ELISA). This antibody, specific for a calcium complex of the peptide antigen, Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys, has found widespread use as a mild purification reagent for Flag-epitope tagged recombinant proteins. Although M1 affinity columns release monovalent Flagged proteins in the absence of calcium, the antibody retains substantial affinity for the Flag sequence even in metal-free conditions, so that it has been impossible to use it to develop a metal-sensitive ELISA assay. This is due to the ability of the antibody to remain bound to polyvalent surface-coated antigen, for instance, when Flagged proteins are bound to ELISA plates or blotting filters. The resultant antigen polyvalence raises the avidity of the Flag antibody to a point where the reaction is essentially calcium-independent. However, when the antibody itself was made monovalent, by proteolytic cleavage to the Fab, this situation was reversed and the ELISA reaction became calcium-dependent. This new metal-dependent ELISA assay was used to explore the metal requirements of the antibody in detail. Among divalent metals, binding tapered off with increasing radius above that of calcium, or with decreasing radius below that of calcium. Several smaller metals, such as nickel, acted as inhibitors of the binding reaction. Substantial binding was demonstrated for heavy metals such as cadmium, lanthanum and samarium. Because it is of interest to use this antibody for the co-crystallization of recombinant Flag-fusion proteins, the ability to bind heavy metals was a significant finding.

Characterization of processing requirements and metal cross-reactivities in T cell clones from patients with allergic contact dermatitis to nickel

Metal ions such as nickel, cobalt, copper and palladium are known to be potent sensitizers in humans, but the antigenic determinants created by these metals as well as the mechanisms of recognition by specific T cell clones are still not elucidated. In this paper, nickel-specific T lymphocyte clones were isolated from four patients exhibiting contact dermatitis to this metal. A panel of 42 independent T cell clones was studied. They were shown to recognize nickel in the context of major histocompatibility complex (MHC) class II molecules and to belong to the CD4 subset. Using fixed autologous Epstein-Barr virus-transformed B cells as antigen-presenting cells (APC), we could distinguish two distinct groups of T cell clones on the basis of processing requirements: 40% of the T cell clones were strictly processing dependent, whereas the remaining 60% could proliferate in response to nickel even in the presence of glutaraldehyde-fixed APC. Furthermore, we present arguments indicating that individual Ni-specific T cell clones cross-react with some transition metals (e.g. Cu or Pd), but not with others (e.g. Co, Cr and Pt), presented by identical MHC class II molecules. These results thus provide an explanation for the multiple metal-reactivities observed in vivo in human patients: they indicate that for Cu and Pd, these co-reactivities in vivo might be due to cross-reactivity at the clonal level. Our findings also suggest that this is not the case for cobalt allergy, which might result from cosensitization of the patient to cobalt in addition to nickel.

Metal ion induced autoimmunity

Metal-induced autoimmunity is a well established but poorly understood phenomenon. Recent work has begun to elucidate the molecular interactions of metal ions with immune cells and self-proteins. Metal-induced presentation of cryptic self-peptides emerges as a possible mechanism for activation of 'metal-specific' T cells, challenging the hypothesis of a random polyclonal activation of T and B cells by metals. A preferential T-helper cell type 2 response is involved in metal ion induced systemic autoimmune disease.

The molecular basis of metal recognition by T cells

T lymphocytes play critical roles in a series of important immune responses, including delayed-type hypersensitivity and contact sensitivity. Metal haptens such as nickel are among the most common sensitizers. In general, T cells recognize fragments of proteins complexed to MHC molecules. Haptens, however, are too small to be antigenic by themselves. Recent experiments have suggested that hapten-specific T cells recognize hapten-modified MHC-peptide complexes. Here I review the data supporting this hypothesis and speculate on the relevance of these findings for the understanding of chemical-induced hypersensitivities.

How the anti-(metal chelate) antibody CHA255 is specific for the metal ion of its antigen: X-ray structures for two Fab'/hapten complexes with different metals in the chelate

Antibodies with bound metal-chelate haptens provide new means for exploiting the diverse properties of metallic elements. The murine monoclonal antibody CHA255 (IgG1 lambda) binds the metal-chelate hapten indium (III)-4-[N'-(2-hydroxyethyl)thioureido]-L-benzyl-EDTA (designated In-EOTUBE) with high affinity (K(a) = 1.1 x 10(10) M-1). Antibody binding is highly specific for the indium chelate; the affinity decreases as much as 10(4) with other metals, even those having ionic radii close to indium. To better understand this selectivity, the crystal structure of the antigen-binding fragment (Fab') of CHA255 complexed with its hapten, In(III)-EOTUBE, was determined by molecular replacement and refined at 2.2-A resolution. The structure of CHA255 Fab' complexed with Fe(III)-EOTUBE was also determined and refined at 2.8-A resolution. In both structures, the hapten's EDTA moiety is half-buried near the center of the complementarity-determining regions (CDR's). Five of the six CDR's on the Fab' interact with the hapten through protein side-chain atoms (but not main-chain atoms). A novel feature of the In-EOTUBE/Fab' complex is coordination of the indium by N epsilon of one histidine from the heavy chain's third CDR (distance = 2.4 A). The histidine coordination is not observed in the Fe-EOTUBE/Fab' complex, due mainly to a slightly different hapten conformation that reduces metal accessibility; this may partially explain the 20-fold lower affinity of CHA255 for iron hapten. An unexpected feature of the Fab' overall is an elbow angle of 193 degrees (the angle between the pseudodyad axes of the Fab's constant and variable domains).

Influence of irritants on lymph node cell proliferation and the detection of contact sensitivity to metal salts in the murine local lymph node assay

Dimethyl sulfoxide (DMSO) and sodium lauryl sulfate (SLS) are known to cause irritation of the skin, and to enhance the penetration of chemicals into the epidermis. In the present study, the lymph node cell (LNC) proliferative response following exposure to irritants, such as SLS and DMSO, was examined in the murine local lymph node assay (LLNA). Exposure to DMSO or SLS aqueous solution induced a small increase in lymph node cell proliferation compared with aqueous solution alone. Exposure to SLS in DMSO caused a significant increase in LNC proliferation. Further, the effect of addition of the irritants in a vehicle on the detection of contact sensitivity to metal allergens was examined. Application of potassium dichromate and nickel sulfate in DMSO or SLS aqueous solution caused increases in LNC proliferation. Exposure to metal allergen with SLS in DMSO also induced a significant LNC proliferative response, but did not induce a significant increase in stimulation index (increase in 3H-thymidine incorporation relative to vehicle-treated control group). This was because of increased 3H-thymidine incorporation following exposure to SLS-DMSO in the control group. These results suggest that irritants enhance the LNC proliferative responses to metal allergens. The use of SLS in aqueous solution is effective for the detection of sensitivity to water-soluble allergens, such as metal allergens, in the LLNA, as well as the use of DMSO as an application vehicle.