Sensitization with Cr, Ni and Zr salts and allergic type granuloma formation in the guinea pig

Nickel: Intrinsic Skin Sensitization Potency and Relation to Prevalence of Contact Allergy

Nickel remains the most commonly identified contact allergen. However, it has proven difficult to demonstrate significant skin-sensitizing activity for nickel in toxicology tests, which typically have indicated a weak skin sensitization potential. Information indicates that in vivo assays are not predictive of dermal sensitization hazard or potency for nickel due to a human-specific mechanistic route for nickel sensitization that animals lack. A similar rationale will apply to in vitro alternatives-although these currently have limited ability to determine intrinsic potency. Generally, in silico methods are not designed for metal allergens and cannot contribute to the analysis. For ethical reasons, human experimental work has been limited, with a single study suggesting moderate potency. Accordingly, it seems reasonable to conclude that the high frequency of contact allergy to nickel in humans is a function of both its intermediate potency coupled with a high level of dermal exposure, particularly to damaged/inflamed skin.

Evaluation of the skin sensitizing potential of biodegradable magnesium alloys

Corroding metals made of magnesium alloys represent a new class of degradable implants for musculoskeletal surgery. These implants may be associated with skin sensitizing reactions because of the release of metal ions. This study was conducted to compare the sensitizing potential of four different magnesium alloys (AZ31, AZ91, WE43, and LAE442) to current implant materials such as titanium (TiAl6V4) and a degradable polymer (SR-PLA96). Solutions and solid chips of these materials were prepared and tested in 156 guinea pigs according to the Magnusson-Kligman test. A standard allergen (hydroxy-cinnamon-aldehyde) causing allergic erythema was used as positive control and a standard irritant (sodium-lauryl-sulfate) causing local skin irritation for less than 24 h was used as negative control. All erythema were graded immediately and 24 h after patch removal by three independent observers. Histomorphological analyses were performed on skin biopsies taken 24 h after patch removal. We found that initial erythema in animals treated with solid chips diminished within 24 h and were caused by local skin irritation. Local skin irritation was also determined in erythema remaining for 24 h after patch removal in animals treated with dissolved test materials. No allergenic reactions according to the histomorphological criteria were observed in skin biopsies. We conclude that no skin sensitizing potential were detected for standard materials as well as for all tested magnesium alloys by the used methods.

Ion leaching from dental ceramics during static in vitro corrosion testing

Dental ceramics are often called inert materials. It can be hypothesized, however, that differences in the composition, microstructure, and environmental conditions will affect the degree of corrosion degradation in an aqueous environment. The aims of the study were, therefore, to study the ion dissolution from glass-phase ceramics, with or without crystalline inclusions, and from all-crystalline ceramics and to compare the effects of different corrosion media. Ceramic specimens were produced from glass-phase and oxide ceramics and given an equivalent surface smoothness, after which they were subjected to in vitro corrosion (Milli-Q water at 37 +/- 2 degrees C for 18 h and 4% acetic acid solution at 80 +/- 2 degrees C for 18 h, respectively). The temperature of the corrosion solution was slowly increased until it reached 80 +/- 2 degrees C to reduce the risk of microcrack formation at the surface. The analyses of ion leakage were performed with inductively coupled plasma optical emission spectroscopy. A large number of inorganic elements leached out from the various dental ceramics. The major leaching elements were sodium and potassium; in the acid-corrosion experiments, there were also magnesium, silicon, and aluminum and, on a lower scale, yttrium, calcium, and chromium. The various glass-phase ceramics displayed significant differences in ion leakage and significantly higher leakage values than all-crystalline alumina and zirconia ceramics. No significant difference in dissolution was found between high and low-sintering glass-phase ceramics or between glass-phase ceramics with high volume fractions of crystallites in the glass phase in comparison with those with lower crystalline content. It can be concluded, therefore, that none of the dental ceramics studied are chemically inert in an aqueous environment.

Evaluation of skin sensitization potential of nickel, chromium, titanium and zirconium salts using guinea-pigs and mice

Contact sensitization capacity of four metal salts, nickel sulphate (NiSO4), potassium dichromate (K2Cr2O7), titanium chloride (TiCl4) and zirconium chloride (ZrCl4), was evaluated using guinea-pigs and mice. In the guinea-pig sensitization tests, we set up an injection concentration to 1% for all chemicals, and changed the challenge concentration. Guinea-pigs were sensitized with NiSO4, K2Cr2O7 and TiCl4. Among the test metal salts, K2Cr2O7 showed the highest sensitization rate and strongest skin reactions. ZrCl4 did not cause any sensitization responses under our experimental conditions. Minimum challenge concentration to cause a skin response was < 0.25% for K2Cr2O7, 0.5% for NiSO4 and 2% for TiCl4, respectively. A sensitive mouse lymph node assay (SLNA) also determined NiSO4 and K2Cr2O7 as a sensitizer. In the SLNA, TiCl4 caused mild lymph node responses, but was classified as a non-sensitizer as well as ZrCl4. Considering these results, the order of sensitization potential was K2Cr2O7 > NiSO4 > ZrCl4. NiSO4- and K2CrO7-sensitized animals did not show any reactions to ZrCl4 and TiCl4. No cross-reaction among these metal salts was found.

Skin disease and contact sensitivity in house painters using water-based paints, glues and putties

A dermatologic investigation of 202 construction painters included patch testing with the TRUE Test standard series and ingredients of water-based paints, glues and putties (painters' series). 32 painters had current eczema and 16 had a history of previous eczema. Of these, 16 and 9, respectively, had current and previous histories of hand eczema. Irritant reactions on the hands, characterized by dry, erythematous finely fissured skin, which healed within a few days of skin rest, were found in 18 painters. 8 painters presented dry, fissured finger tips and finger sides. The total group of painters had 25 allergic reactions to the TRUE Test standard series and 11 to the painters' series. 11 test reactions were found to be related to present or previous hand eczema: 4 cases reacted to nickel, cobalt, colophony or N-octyl-isothiazolinone; 2 each to p-tertbutylphenol-formaldehyde resin and benzisothiazolinone (BIT); and 3 to Cl + Me-isothiazolinone. 5 painters were sensitive to BIT without clinical symptoms of skin disease. Hand eczema is no more common among construction painters who work with water-based paints, glues and putties, than in an average population. There are, however, special risks of sensitization and eczema in a construction painter's work that should be considered on employment.

Physiological and toxicological changes in the skin resulting from the action and interaction of metal ions

The human environment contains more than 50 metal or metalloid elements. At least 15 are recognized as trace elements, with zinc, calcium, copper, magnesium, and iron having specific roles in skin morphogenesis and function. The present review focuses on the presumed role of metal ions in the skin, their competition for carrier proteins, and membrane receptors. Evidence presented shows that the balance of trace metal ions is critical for normal skin and repair mechanisms following injury. Xenobiotic ions can impair this balance, leading to pathological change. The skin acts as an organ of elimination of excess trace metals and xenobiotic ions from the body, but mechanisms of voidance vary for different metals. Metal ions are an important cause of allergies, and evidence is presented to show that the majority of metals or metal compounds can induce allergic changes. Except for chromium and nickel, which are among the most common human allergens, animal models have provided little information. At least cadmium, thorium, lead, chromium, nickel, beryllium, and arsenic and proven or putative carcinogens in animals or humans on the basis of cytological or epidemiological evidence. However, only arsenic exhibits a clear predilection for the skin. Other metals such as gold can induce subcutaneous sarcoma following injection, but the relevance of this observation in terms of human occupational risk is discounted.

The performance of the local lymph node assay with chemicals identified as contact allergens in the human maximization test

For many years, tests in the guinea pig have been the favoured option for the identification of the skin sensitization potential of chemicals. However, the mouse has been used widely in immunology research and can represent a viable alternative. A variety of murine assays have been described, including several methods based on ear swelling as an endpoint. Another option is to assess induced lymph node cell proliferation and it is this which forms the basis of the murine local lymph node assay (LLNA). The LLNA has undergone several successful interlaboratory validations and compares well with standard guinea pig assays. In the present study, the performance of the LLNA was examined with chemicals tested previously in the human maximization test (HMT). 30 chemicals, 23 of which proved positive in the HMT and seven of which were negative, have been tested. All but four of the materials found positive in the HMT also tested positive in the LLNA. Of these four, sulfanilamide and paraben esters would not classify as skin sensitizers in the guinea pig maximization test and nickel has been found to yield variable results in a number of predictive animal tests. Of the seven substances which proved negative in the HMT, six were also negative in the LLNA, the exception being sodium dodecyl sulfate. These data demonstrate that the LLNA is able to identify accurately chemicals which have the potential to cause significant allergic contact dermatitis in humans.

Zirconium granuloma resulting from an aluminum zirconium complex: a previously unrecognized agent in the development of hypersensitivity granulomas

Zirconium compounds have been associated with the development of hypersensitivity granulomas. However, aluminum zirconium complexes have not previously been shown to induce sensitization. We present the clinical and histologic findings of a case in which a patient developed an acute hypersensitivity reaction to an aluminum zirconium complex.

Metals and the skin

Certain metals, and many metal-based compounds, are inherently toxic, and their presence in occupational and environmental settings raises appropriate questions concerning human exposure. Contact of these materials with the skin represents an important route of exposure, which is not well characterized. The purpose of this review, therefore, is to assemble the available, useful information pertinent to risk assessment following dermal contact. Specifically, we summarize here: (1) data relevant to the qualitative and (where possible) quantitative evaluation of metal compound permeation through the skin; (2) the role of each metal in metabolism, particularly with respect to the skin, and the potentially toxic effects that may result from dermal contact; and (3) the immunological characteristics (including allergenicity) of the metals and their derivatives. In total, information on 31 metals has been reviewed. It is clear that many diverse factors determine the ability of metal-based species to permeate biological membranes, not all of which have been fully defined. Therefore, considerably more experimentation, targeted at the development of high-quality transport data, will be required before the specification of practically useful structure-activity relationships are possible.

Zirconium. An abnormal trace element in biology

The action of Zirconium (Zr) on biological systems presents an enigma. It is ubiquitous, being present in nature in amounts higher than most trace elements. It is taken up by plants from soil and water and accumulated in certain tissues. The entry into animal systems in vivo is related to the mode of exposure and the concentration in the surrounding environment. Retention is initially in soft tissues and then slowly in the bone. The metal is able to cross the blood brain-barrier and is deposited in the brain and the placental barrier to enter milk. The daily human uptake has been known to be as high as 125 mg. The level of toxicity has been found to be moderately low, both in histological and cytological studies. The toxic effects induced by very high concentrations are nonspecific in nature. Despite the presence and retention in relatively high quantities in biological systems, Zr has not yet been associated with any specific metabolic function. Very little information is available about its interaction with the compounds of the genetical systems, such as nucleic acids. Apparently, the metal is neither an essential nor toxic element in the conventional sense. However, the increasing exposure to this element through its increasing use in new materials and following radioactive fallout, has increased the importance of the study of its effects on living organisms. The tetravalent nature of the ionic state and the high stability of the compounds formed are important factors that need to be considered, as also the accumulation of this element in the brain, reminiscent of the relationship between Al3+ and Alzheimer's disease.

Oral induction of immunological tolerance to chromium in the guinea pig

Metal alloys used in dentistry may elicit adverse side-effects. Contact allergic reactions to metals released from such alloys are among the most frequently encountered problems. In an earlier study, we observed that oral contacts with nickel or chromium salts did not sensitize, but rather decreased the risk of subsequent sensitization to these metals. In the present study, we focused on chromium allergy and extended our earlier observations by further dose-response studies. In addition, we compared different chromium valencies as to their potential oral tolerogenic effects. Development of immunological tolerance in chromium-fed guinea pigs was demonstrated by their inability to develop chromium hypersensitivity after a subsequent immunization attempt. For these studies, the techniques of immunization and skin testing were first improved. One feeding with a high dose of K2Cr2O7 (containing hexavalent chromium) was effective in full tolerance induction. In contrast, trivalent chromium (CrCl3) induced a distinctly lower degree of tolerance, whereas metallic chromium powder was not detectably tolerogenic after a limited number of feedings. Dose-frequency-response studies with K2Cr2O7 showed that full tolerance could also be induced by an increase in the number of feedings with sub-optimal tolerogenic doses. The present results therefore support our hypothesis that long-lasting oral contact with chromium-releasing metal alloys may ultimately result in strong immune tolerance to this metal in subjects without previous skin contact with it. This view is further supported by recent insights into the unique tolerogenicity of oral, as compared with gastro-intestinal, allergenic contacts.

Experimental sensitization of guinea-pigs to nickel and patch testing with metal samples

Two groups each of 30 guinea-pigs were painted on 5 days/wk for 4 wk with 1% nickel sulphate in lanolin. The dose was applied to the shaved dorsal skin, which was prepared daily before treatment with sodium lauryl sulphate and injected intradermally each week during this period with 0.1 ml 1% potassium alum in distilled water, close to the site of NiSO4 application. Of the two groups of guinea-pigs submitted to this epicutaneous procedure, 63 and 80% developed skin allergy in response to challenge with 2% NiSO4 after a rest period of 2 wk, whereas no sensitization response was elicited by 1% NiSO4 in the guinea-pig maximization test. When two further groups were sensitized by the epicutaneous procedure, the first group, with a sensitization rate of 52% at the first challenge, showed no decline in response with five successive monthly challenges. Addition of NiCl2 to the drinking-water of the second group did not increase the sensitization rate induced by the monthly rechallenges with NiSO4. In guinea-pigs allergic to nickel, plating of Ni-coated brass discs with chromium as a special surface treatment prevented the occurrence of the contact allergy elicited by brass discs coated with Ni alone, whereas plating with gold/copper/cadmium did not.

Review of the toxicity of multifunctional acrylates

Multifunctional acrylates and methacrylates (MFA) represent a class of materials with considerable chemical reactivity that are used in many applications with opportunity for contact exposure. They represent appreciable eye and skin contact hazards, and several members of the class may be absorbed from skin to cause systemic effects. A number of MFAs have been identified as sensitizers. While the acute toxicity of MFAs is certain, the effects of repeated or chronic exposure are less clear. Data are presented that suggest that MFAs are not appreciable fetotoxic or teratogenic hazards and do not elicit a strong carcinogenic response following chronic dermal exposure. The use of these data for product safety purposes and research needs is discussed.

The mononuclear phagocyte system in granulomas

A comparison is made between immunologically induced and non-immunologically induced granulomas in guinea-pigs injected with metals (zirconium and aluminum) or with mycobacteria (BCG vaccine and Mycobacterium leprae). Immunological granulomas were characterized by epithelioid cells and fibrosis, whereas non-immunological granulomas contained phagocytosing macrophages with little evidence of fibroblast activation. Epithelioid cells carry the same specific macrophage antigen as phagocytosing macrophages and this can be detected by the use of a specific monoclonal antibody. However, they differ from phagocytosing macrophages in that they are poorly phagocytic, not glass adherent and lack Ia antigen. They are however secretory cells with rough endoplasmic reticulum. A relation between the presence of these cells and increased collagen synthesis is indicated. A study of accessory cell function showed that the epithelioid cells of BCG granulomas were able to support mitogen-induced but not antigen-induced proliferation of T lymphocytes. The macrophages of M. leprae granulomas did not support either a mitogen- or antigen-induced proliferative response.

Concepts of granulomatous inflammation

Table 8 lists the patterns of the five discrete tissue reaction patterns of granulomatous inflammation and relates them to the predominant microscopic tissue reaction as well as to the dominant cell type present in the infiltrate. The possibility of a sixth group, granulation tissue, was also considered for this classification schema. The term "granulation tissue" was used by Virchow to define granulomatous inflammation. He probably used this term in a broader context than our present definition of granulation tissue (ie, fibrocapillary proliferation). Using the more narrow and perhaps more precise definition, we think that granulation tissue does not constitute a form of granulomatous inflammation.

Attempts to induce contact allergy to nickel in the mouse

Various attempts to sensitize mice to nickel salts are described. The antigen was applied once or repeatedly by the epicutaneous or intracutaneous route and by combinations of the two. The procedures included prior irritation of the skin, treatment with Freund's complete adjuvant, cyclophosphamide or Tetramisol, and prior sensitization to picryl chloride. Contact allergy was achieved only by repeated epicutaneous application of a strong nickel solution over a 3-week period. The resulting dermatitis was demonstrated by a weak but significant wet weight increase of inflamed skin.

Granulomatous inflammation--a review

The granulomatous inflammatory response is a special type of chronic inflammation characterised by often focal collections of macrophages, epithelioid cells and multinucleated giant cells. In this review the characteristics of these cells of the mononuclear phagocyte series are considered, with particular reference to the properties of epithelioid cells and the formation of multinucleated giant cells. The initiation and development of granulomatous inflammation is discussed, stressing the importance of persistence of the inciting agent and the complex role of the immune system, not only in the perpetuation of the granulomatous response but also in the development of necrosis and fibrosis.

Contact sensitivity to acrylate compounds in guinea pigs

As reports of contact dermatitis in humans due to acrylate compounds have increased considerably in recent years, it was decided to investigate the ability of these chemicals to evoke contact sensitivity skin reactions in guinea pigs. 21 different acrylate and methacrylate compounds were scanned for their ability to induce contact sensitivity, using 5 different sensitization protocols. Contact reactions of varying intensities were produced to all the mono-, di- and triacrylates tested. However, it was not possible to sensitize guinea pigs to any methacrylates. It would appear that guinea pigs cannot be contact sensitized to acrylate chemicals that are substituted on carbon 2.

Experimental model for dermal granulomatous hypersensitivity in Q fever

Q fever has been associated with granulomatous changes in clinical biopsy material obtained from liver and bone marrow. Local reactions to skin testing have been described in previously sensitized humans, but histological studies of such reactions have not been reported. We note that delayed hypersensitivity reactions to whole-cell phase I Q fever vaccine in immunized guinea pigs have a time course of development of induration characteristic of granulomatous hypersensitivity. Histological examination of such skin reactions on day 9 after testing revealed epithelioid cell infiltration and the presence of large numbers of multinucleated giant cells. Prominent in the sections were fragments of disintegrating polymorphonuclear leukocytes having the appearance of leukocytoclasis. Electron microscopic studies confirmed the presence of epithelioid changes in cells of the mononuclear phagocyte series, as well as extensive collagen deposition. This animal system affords a readily reproducible model of dermal granulomatous hypersensitivity and an opportunity to analyze the immunological basis of this reaction.

The origin, morphology, and function of epithelioid cells

Epithelioid cells are cells of the mononuclear phagocyte system found in certain granulomas mainly associated with intense immunological activity. These cells show little phagocytic activity. In certain experimental granulomas such as those produced in guinea pigs sensitive to zirconium, and at sites of intense inflammatory reaction in man, they may contain varying amounts of rough endoplasmic reticulum ("secretory" epithelioid cells). In other situations such as tuberculoid leprosy and in some cases of sarcoidosis they may have the appearance of activated macrophages or take on a multivesicular appearance ("vesicular" epithelioid cells). It is suggested that "vesicular epithelioid cells could develop from "secretory" epithelioid cells by a process of degeneration. In studies comparing granulomas induced in lymph nodes draining the site of intradermal injection of mycobacteria, epithelioid cell granulomas were produced with BCG vaccine, whereas, the granulomas induced by Mycobacterium leprae contained undifferentiated macrophages that contained phagocytosed organisms. The BCG granulomas were in addition characterised by fibroblast infiltration, the presence of collagen and resolution by fibrosis. M. leprae granulomas showed little evidence of fibroblastic activity. Biochemical studies confirmed that BCG granulomas formed new collagen in vitro, whereas this did not take place with M. leprae granulomas. It is suggested that epithelioid cells could play an important role in fibrosis possibly by the secretion of a fibroblast activating factor.

Formation of multinucleated giant cells from human monocyte precursors. Mediation by a soluble protein from antigen-and mitogen-stimulated lymphocytes

Multinucleated giant cells are associated with granulomas arising from immunological and nonimmunological inflammatory reactions. They are an integral part of the host immune response to chronic infectious diseases. In the present study we have demonstrated that human lymphocytes when stimulated by specific antigens of T cell mitogens produce a soluble factor that causes peripheral blood monocytes to fuse and form multinucleated giant cells in vitro. Production of the giant cell factor by antigen-stimulated peripheral blood lymphocytes correlates with the existence of cell-mediated immunity to specific antigen. Monocyte-depleted blood lymphocytes, but not purified blood monocytes, produce the giant cell factor when cultured with antigens or T cell mitogens. Gel filtration and physiochemical studies indicate that the lymphocyte-derived giant cell factor is a heat-labile protein of approximately 60,000 mol wt. These findings suggest that multinucleated giant cells in granulomas may be formed by fusion of circulating monocytes in response to the release of a 60,000-mol wt protein from antigen-stimulated T lymphocytes.

The monocyte-macrophage system in granulomatous inflammation

Granulomas may be immunologically induced or non-immunologically induced. In immunologically induced granulomas cells of the monocyte-macrophage series take on the appearance of epitheloid cells. Ultrastructurally epithelioid cells may have a secretory appearance with much rough endoplasmic reticulum or take on highly degenerate vesicular appearance. Other epithelioid cells look like activated macrophages. Secretory epithelioid cells may be found associated with acute local inflammation as in borderline tuberculoid leprosy in reaction, the lepromin reaction, following injection of BCG vaccine and in experimental zirconium granulomas. In these situations there may also be strong histological and biochemical evidence of increased fibroblast activity and collagen synthesis. It is suggested that these cells are actively secreting a fibroblast-activating factor. Epithelioid cells may lose their Fc receptors, undifferentiated macrophages in lepromatous leprosy can lose their C3 receptors. It is suggested that in a number of situations granuloma formation may be associated with complement activation through the alternative pathway as in the case of mycobacterial granulomas. Toxic granulomas produced by metals may be caused by C3 being split by plasmin after conversion from plasminogen by activation of the Hageman factor.

Immunologic and nonimmunologic activation of macrophages

Cells of the mononuclear phagocyte system take on different morphological features and appear to have different functions in immunological and nonimmunological granulomas. In immunological granulomas the appearance is of epitheliod cells. Epitheliod cells are of 2 types. In borderline tuberculoid leprosy granulomas, the appearance is of activated macrophages. Similar activation can be induced by lymphokine which increases respiratory enzyme activity. Other types of epithelioid cell are found in experimental zirconium granulomas. These cells contained rough endoplasmic reticulum, indicating that they may play a secretory role. It is suggested that these cells could play a part in stimulating fibrosis. Other substances that produce nonimmunological granulomas, such as aluminum containing compounds, are directly toxic to macrophages in vitro resulting in the rapid release of cytoplasmic enzymes. These compounds also activate complement, causing C3 conversion and anaphylatoxin production. C3 conversion may be through pathways other than the classical and alternative pathways and does not occur in the absence of plasminogen. Mycobacteria can activate complement through the alternative pathway, suggesting a mechanism for granuloma formation in lepromatous leprosy. Loss of C3 membrane receptors from macrophages in lepromatous leprosy could be produced by feeding peritoneal exudate macrophages with mycobacteria in vitro. This was not just due to phagocytosis, as a similar receptor loss was not obtained when the cells were fed latex particles or zymosan. Epithelioid cells in tuberculoid leprosy and sarcoidosis lose Fc membrane receptors but retain C3 receptors. Thus epithelioid cells can be readily distinguished from other cells of the mononuclear phagocyte series.