Pilots Notes Lysander III and IIIAAeroplanes

Руководство для пилота самолета Lysander III и IIIA.

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Nevertheless, in sensitized individuals, type-2 T-cells also play a role, as shown by both IL-4 production and allergen-specific type-2 T-cells in the blood and at ACD reaction sites (see Sect. 7, “The Effector Phase of Allergic Contact Dermatitis”) [135–137]. Their role may increase along with the longevity of sensitization, since several factors contribute to shifting type-1 to type-2 responses, including reversibility of the former and not of the latter T-cells, as mentioned above [138]. After mucosal contacts with contact allergens, type-2 T-cell responses are most prominent.

These pro-inflammatory phenomena, which are also observed in nonsensitized individuals [202] and in Tcell-deficient nude mice [203], strongly contribute to allergenicity [5]. Clearly most, if not all, of these effects can also be caused by irritants and, therefore, do not unambiguously discriminate between irritants and contact allergens [204–206]. Probably, true differences between these types of compounds depend on whether or not allergen-specific T-cells become involved. , local release of certain chemokines, such as CXCL10 (IP-10) and CXCL11 (I-TAC/IP-9) [207].

2 Activation of Hapten-Specific T-Cells As outlined in Sect. 2,“Binding of Contact Allergens to Skin Components,” the chemical nature of the hapten determines its eventual cytoplasmic routing in antigen-presenting cells (APC), and thus whether presentation will be predominantly in context of MHC class I or II molecules (Fig. 2). T cells, expressing CD8 or CD4 molecules, can recognize the haptenMHC class I or II complex, which in turn stabilizes MHC membrane expression [84, 85]. Chances of productive interactions with T-cells are high since each MHC–allergen complex can trigger a high number of T-cell receptor (TCR) molecules (“serial triggering”) [86].

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