BackgroundAllergy diagnosis by determination of allergen-specific IgE is complicated by clinically irrelevant IgE, of which the most prominent example is IgE against cross-reactive carbohydrate determinants (CCDs) that occur on allergens from plants and insects. Therefore, CCDs cause numerous false-positive results. Inhibition of CCDs has been proposed as a remedy, but has not yet found its way into the routine diagnostic laboratory. We sought to provide a simple and affordable procedure to overcome the CCD problem.MethodsSerum samples from allergic patients were analysed for allergen-specific IgEs by different commercial tests (from Mediwiss, Phadia and Siemens) with and without a semisynthetic CCD blocker with minimized potential for nonspecific interactions that was prepared from purified bromelain glycopeptides and human serum albumin.ResultsTwenty two per cent of about 6000 serum samples reacted with CCD reporter proteins. The incidence of anti-CCD IgE reached 35% in the teenage group. In patients with anti-CCD IgE, application of the CCD blocker led to a clear reduction in read-out values, often below the threshold level. A much better correlation between laboratory results and anamnesis and skin tests was achieved in many cases. The CCD blocker did not affect test results where CCDs were not involved.ConclusionEliminating the effect of IgEs directed against CCDs by inhibition leads to a significant reduction in false-positive in vitro test results without lowering sensitivity towards relevant sensitizations. Application of the CCD blocker may be worthwhile wherever natural allergen extracts or components are used.

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The autograft principle results in postoperative long-term survival comparable with that of the age- and gender-matched general population and reoperation rates within the 1%/patient-year boundaries and should be considered in young, active patients who want to avoid the shortcomings of conventional prostheses.

The α-Gal syndrome (AGS) is a type of allergy characterized by an IgE antibody (Ab) response against the carbohydrate Galα1-3Galβ1-4GlcNAc-R (α-Gal), which is present in glycoproteins from tick saliva and tissues of non-catarrhine mammals. Recurrent tick bites induce high levels of anti-α-Gal IgE Abs that mediate delayed hypersensitivity to consumed red meat products in humans. This was the first evidence that tick glycoproteins play a major role in allergy development with the potential to cause fatal delayed anaphylaxis to α-Gal-containing foods and drugs and immediate anaphylaxis to tick bites. Initially, it was thought that the origin of tick-derived α-Gal was either residual blood meal mammalian glycoproteins containing α-Gal or tick gut bacteria producing this glycan. However, recently tick galactosyltransferases were shown to be involved in α-Gal synthesis with a role in tick and tick-borne pathogen life cycles. The tick-borne pathogen Anaplasma phagocytophilum increases the level of tick α-Gal, which potentially increases the risk of developing AGS after a bite by a pathogen-infected tick. Two mechanisms might explain the production of anti-α-Gal IgE Abs after tick bites. The first mechanism proposes that the α-Gal antigen on tick salivary proteins is presented to antigen-presenting cells and B-lymphocytes in the context of Th 2 cell-mediated immunity induced by tick saliva. The second mechanism is based on the possibility that tick salivary prostaglandin E2 triggers Immunoglobulin class switching to anti-α-Gal IgE-producing B cells from preexisting mature B cells clones producing anti-α-Gal IgM and/or IgG. Importantly, blood group antigens influence the capacity of the immune system to produce anti-α-Gal Abs which in turn impacts individual susceptibility to AGS. The presence of blood type B reduces the capacity of the immune system to produce anti-α-Gal Abs, presumably due to tolerance to α-Gal, which is very similar in structure to blood group B antigen. Therefore, individuals with blood group B and reduced levels of anti-α-Gal Abs have lower risk to develop AGS. Specific immunity to tick α-Gal is linked to host immunity to tick bites. Basophil activation and release of histamine have been implicated in IgE-mediated acquired protective immunity to tick infestations and chronic itch. Basophil reactivity was also found to be higher in patients with AGS when compared to asymptomatic α-Gal sensitized individuals. In addition, host resistance to tick infestation is associated with resistance to tick-borne pathogen infection. Anti-α-Gal IgM and IgG Abs protect humans against vector-borne pathogens and blood group B individuals seem to be more susceptible to vector-borne diseases. The link between blood groups and anti-α-Gal immunity which in turn affects resistance to vector-borne pathogens and susceptibility to AGS, suggests a trade-off between susceptibility to AGS and protection to some infectious diseases. The understanding of the environmental and mole...

Cross-reactive carbohydrate determinants of plants are essentially a mixture of N-glycans containing beta1,2-xylose and core alpha1,3-fucose, the latter also found in insect glycoproteins. To determine the relative contributions of these two sugar residues to antibody binding, we prepared an array of glycomodified forms of human apo-transferrin. Using core-alpha1, 3-fucosyltransferase (EC 2.4.1.214) and beta1,2-xylosyltransferase (EC 2.4.2.38) recombinantly expressed in Pichia pastoris and suitable glycosidases, glycoforms containing either only fucose (MMF), only xylose (MMX), both (MMXF), or neither (MM) linked to the common pentasaccharide core were generated. Additional glycoforms were obtained by enzymatic removal of the alpha1,3-linked mannosyl residue. These transferrin glycoforms served to define the binding specificity of antibodies in western blot, ELISA, and inhibition ELISA. Rabbit anti-horseradish peroxidase serum bound to both the fucosylated (MMF) and the xylosylated (MMX) glycoforms. Inhibition studies indicated two independent highly specific populations reacting with either of the two epitopes. In contrast, the monoclonal antibody YZ1/2.23 appears to recognize a larger structure including both the fucosyl and the xylosyl residue. The mannose-deficient glycoform was a poorer inhibitor for both antibodies. Terminal GlcNAc residues prevented antibody binding. Rabbit anti-bee venom serum reacted with fucosylated forms (MMF and MMXF) only. Experiments with sera from allergic patients suggest that glycomodified human transferrin, especially the MMXF glycoform, is a suitable reagent for the detection of antibodies against cross-reactive carbohydrate determinants. Within the panel studied, several sera contained high levels of fucose-reactive IgE but only a few sera showed any binding to MMX-transferrin.