Streit M, Braathen L R
Dermatological University Clinic, Inselspital, Berne, Switzerland.
Acta Odontol Scand. 2001 Oct;59(5):309-14. doi: 10.1080/000163501750541183.
Contact dermatitis or eczema is a polymorphic inflammation of the skin. It occurs at the site of contact with irritating or antigenic substances. In the acute phase there is occurrence of itching erythema, papules, and vesicles, whereas in the chronic phase there is dryness, hyperkeratosis, and sometimes fissures. Contact dermatitis can be divided into irritant and allergic types. Allergic contact dermatitis is a type-IV T-cell-mediated reaction occurring in a sensitized individual after contact with the antigen/allergen. Such antigens are usually low molecular weight substances (MW approximately 500), called haptens; 3000 contact allergens are known. The diagnosis of contact allergy is made on the basis of the history, clinical findings, and a positive epicutancous test result. Allergic, but not irritative, contact dermatitis can spread beyond the area of contact to other body parts. Eczematous lesions are characterized by a mononuclear infiltrate consisting mainly of T cells in the dermis and epidermis, together with an intercellular epidermal edema that is. spongiosis. In allergic contact dermatitis, skin-applied antigen is taken up by epidermal Langerhans cells and transported with the afferent lymph to the regional lymph nodes. Here, naive T lymphocytes are sensitized to become antigen-specific effector T cells, which then leave the lymph node, enter the circulation, and are recruited to the skin by means of specific cell surface molecules, to form the infiltrates. Cytokines released by infiltrating T cells eventually cause keratinocyte apoptosis.
接触性皮炎或湿疹是皮肤的多形性炎症。它发生在与刺激性或抗原性物质接触的部位。急性期会出现瘙痒性红斑、丘疹和水疱，而慢性期则会出现皮肤干燥、角化过度，有时还会出现裂隙。接触性皮炎可分为刺激性和过敏性两类。过敏性接触性皮炎是一种IV型T细胞介导的反应，发生在已致敏个体接触抗原/变应原之后。这类抗原通常是低分子量物质（分子量约为500），称为半抗原；已知有3000种接触性变应原。接触性过敏的诊断基于病史、临床表现以及阳性的皮肤试验结果。过敏性而非刺激性接触性皮炎可从接触部位扩散至身体其他部位。湿疹性皮损的特征是真皮和表皮主要由T细胞组成的单核细胞浸润，以及细胞间表皮水肿即海绵形成。在过敏性接触性皮炎中，皮肤表面的抗原被表皮朗格汉斯细胞摄取，并通过输入淋巴管转运至局部淋巴结。在此，初始T淋巴细胞被致敏成为抗原特异性效应T细胞，这些细胞随后离开淋巴结，进入循环系统，并通过特定的细胞表面分子被招募至皮肤，形成浸润。浸润的T细胞释放的细胞因子最终导致角质形成细胞凋亡。
