Memory T helper cells identify patients with nickel, cobalt, and chromium metal allergy.

BACKGROUND: Patch testing is the gold standard for identifying culprit allergens in allergic contact dermatitis; however, it is laborious and positive reactions are difficult to quantitate. Development of complementary in vitro tests is, therefore, of great importance. OBJECTIVES: This study aimed to improve the in vitro lymphocyte proliferation test (LPT) to detect allergic responses to nickel (Ni), cobalt (Co), and chromium (Cr). METHODS: Twenty-one metal allergic patients with a positive patch test to Ni (n=16), Co (n=8), and Cr (n=3) and 13 controls were included. All were tested by a flow cytometric LPT. RESULTS: Metal-reactive cells were identified as T helper (Th) cells with high expression of the memory marker CD45RO. Skin-homing (cutaneous lymphocyte-associated antigen positive [CLA+]) Ni-reactive memory Th (Thmem hi ) cells identified individuals with a positive patch test for Ni with 100% sensitivity (95% confidence interval [CI] 81%-100%) and 92% specificity (95% CI 67%-100%). Moreover, Co-specific Thmem hi cells expressing CCR6 identified patients with a positive patch test for Co with 63% sensitivity (95% CI 31%-86%) and 100% specificity (95% CI 77%-100%). In Cr allergic individuals, Cr-reactive Thmem hi cells tended to increased CLA and CCR6 expression. CONCLUSION: Metal-reactive Th cells with high expression of CD45RO and coexpression of CLA and CCR6 improved the LPT, making it an attractive supplement to the patch test.

Transition metal sensing by Toll-like receptor-4: next to nickel, cobalt and palladium are potent human dendritic cell stimulators.

BACKGROUND: Nickel was recently identified as a potent activator of dendritic cells through ligating with human Toll-like receptor (TLR)-4. OBJECTIVES: Here, we studied an extended panel of transition metals neighbouring nickel in the periodic table of elements, for their capacity to activate human monocyte-derived dendritic cells (MoDCs). METHODS: The panel included chromium, cobalt, and palladium, all of which are known to be frequent clinical sensitizers. MoDC activation was monitored by assessment of release of the pro-inflammatory mediator interleukin (IL)-8, a major downstream result of TLR ligation. Results The data obtained in the present study show that cobalt and palladium also have potent MoDC-activating capacities, whereas copper and zinc, but not iron and chromium, have low but distinct MoDC-activating potential. Involvement of endotoxin contamination in MoDC activation was excluded by Limulus assays and consistent stimulation in the presence of polymyxin B. The critical role of TLR4 in nickel-induced, cobalt-induced and palladium-induced activation was confirmed by essentially similar stimulatory patterns obtained in an HEK293 TLR4/MD2 transfectant cell line. CONCLUSIONS: Given the adjuvant role of costimulatory danger signals, the development of contact allergies to the stimulatory metals may be facilitated by signals from direct TLR4 ligation, whereas other metal sensitizers, such as chromium, may rather depend on microbial or tissue-derived cofactors to induce clinical sensitization.

High affinity anti-inorganic material antibody generation by integrating graft and evolution technologies: potential of antibodies as biointerface molecules.

Recent advances in molecular evolution technology enabled us to identify peptides and antibodies with affinity for inorganic materials. In the field of nanotechnology, the use of the functional peptides and antibodies should aid the construction of interface molecules designed to spontaneously link different nanomaterials; however, few material-binding antibodies, which have much higher affinity than short peptides, have been identified. Here, we generated high affinity antibodies from material-binding peptides by integrating peptide-grafting and phage-display techniques. A material-binding peptide sequence was first grafted into an appropriate loop of the complementarity determining region (CDR) of a camel-type single variable antibody fragment to create a low affinity material-binding antibody. Application of a combinatorial library approach to another CDR loop in the low affinity antibody then clearly and steadily promoted affinity for a specific material surface. Thermodynamic analysis demonstrated that the enthalpy synergistic effect from grafted and selected CDR loops drastically increased the affinity for material surface, indicating the potential of antibody scaffold for creating high affinity small interface units. We show the availability of the construction of antibodies by integrating graft and evolution technology for various inorganic materials and the potential of high affinity material-binding antibodies in biointerface applications.

Free radicals in antigen formation: reduction of contact allergic response to hydroperoxides by epidermal treatment with antioxidants.

BACKGROUND: For patients with allergic contact dermatitis, the main therapy is anti-inflammatory steroids, a non-specific and symptomatic treatment. In contact allergy, the antigen formation is considered to be the binding of a chemical (hapten) to a biological macromolecule, e.g. a protein. Limonene-2-hydroperoxide (Lim-OOH) is a hapten with a known allergenic effect. It is likely to bind to proteins in the skin via a radical mechanism. It might be possible to inhibit the allergic reaction by epidermal application of substances that can trap free radicals, e.g. antioxidants such as ascorbic acid or alpha-tocopherol, prior to the application of the hapten. OBJECTIVES: To study the influence of antioxidants on the allergenic effect of Lim-OOH in sensitization experiments on guinea pigs. METHODS: Pretreatment with the antioxidants was performed before induction to study the effect on sensitization as well as before challenge testing to study the effect on elicitation. RESULTS: A reduction in the response rate was found both at sensitization and at elicitation. The antioxidants had no effect on cobalt allergy or on the allergenic effect of haptens that form antigens via nucleophilic-electrophilic reactions. No reduction of the effect was seen for irritants. CONCLUSIONS: The protective effect of antioxidants in elicitation could be of practical therapeutic value, as it indicates a possibility for the treatment of patients who have become sensitized to haptens that form full antigens via a radical mechanism.