Generalized cold urticaria: detection of heat-sensitive passive transfer substance active at moderate temperature

Allergy and the skin

Allergic skin disorders include urticaria, angioedema, contact dermatitis and atopic dermatitis, but the model fitting most closely the systemic concept of allergy is atopic dermatitis (AD), the pathogenesis of which is linked to a complex interaction between skin barrier dysfunction and environmental factors such as allergens and microbes. In particular, an important advance was the demonstration that the mutation of the skin barrier protein filaggrin is related strictly to allergen sensitization and to the development of asthma in subjects with AD. The altered skin barrier function, caused by several factors, results in the passage of allergens through the skin and to systemic responses. A pivotal role in such a response is exerted by Langerhans cells which, via their immunoglobulin E (IgE) receptor, capture the allergens and present them to T cells. When T helper type 2 (Th2) cells are activated, the production of a proinflammatory cytokines and chemokines pattern sustains the persistence of inflammation. Known AD-related cytokines are interleukin (IL)-5, IL-13 and tumour necrosis factor (TNF)-alpha, with emerging importance for IL-17, which seems to drive airway inflammation following cutaneous exposure to antigens, and IL-31, which is expressed primarily in skin-homing Th2 cells. Skin-homing is another crucial event in AD, mediated by the cutaneous lymphocyte-associated antigens (CLA) receptor, which characterizes T cell subpopulations with different roles in AD and asthma.

Temperature-dependent skin disorders

The skin is important in preserving homeostasis between man and his environment. One main role of the skin is in thermoregulation, where cutaneous blood flow, and hence skin temperature, vary widely in order to help preserve core body temperature. Under extreme conditions, frostbite or burns may occur. Prolonged exposure to moderate degrees of heat or cold can result in erythema ab igne and chilblains. Temperature plays a direct role in some of the physical urticarias and is one of several important pathogenic factors in conditions such as Raynaud's syndrome, cold panniculitis, and cryoglobulinemia. These and other temperature-dependent skin disorders are reviewed.

Prostaglandin D2 and histamine release in cold urticaria

Prostaglandin (PG) D2 and histamine concentrations have been measured in blood draining cold-challenged forearm skin in patients with cold urticaria. Local venous concentrations of both histamine and PGD2 rose in four patients who developed a whealing response. Plasma histamine concentration increased from a mean resting value of 0.24 +/- 0.09 (SD) ng/ml to peak values of 16.9 to 96.6 ng/ml. Resting concentrations of PGD2 were below the limit of detection (5 pg/ml) in three patients and 62 and 27 pg/ml in the fourth. Peak plasma PGD2 concentration after challenge ranged from 166 to 279 pg/ml. Time course of histamine and PGD2 release was similar with peak concentrations at 6 and 10 minutes, respectively. The maximum clinical response occurred between 10 and 20 minutes after challenge. Our findings demonstrate that PGD2 is produced in association with mast cell degranulation in man, but the amount, relative to histamine, is low. Despite its high potency in production of inflammatory effects, PGD2 probably has only minor direct effects in cold urticaria, although it may act to potentiate other mediators.

Dermographism (mechanical urticaria) mediated by IgM

Sera of three patients with symptomatic mechanical urticaria caused an immediate weal and flare reaction when injected intracutaneously into related recipients, and serum of one patient caused the same reaction in his own skin. Pretreatment of test skin sites with Compound 48/80 abolished or greatly reduced the reaction. This weal-producing substance was found in the same fraction as IgM in Sephadex G-200 gel filtration, was stable to heat treatment (56 degrees C, 4 h) and labile to 2-mercaptoethanol treatment. An immunoadsorption study using anti-IgM serum identified this weal-producing substance as IgM.