Robert M. Barr

Anti-FcϵRI autoantibodies and basophil histamine releasability in chronic idiopathic urticaria☆☆☆★★★♢

Abstract Background: Circulating functional autoantibodies to the high-affinity IgE receptor (FcϵRI) or to IgE have been found in approximately one third of patients with chronic idiopathic urticaria (CIU). Objective: We sought to compare basophil histamine release and basophil numbers in patients with CIU with and without autoantibodies. Methods: Basophil histamine release to the anti-FcϵRI mAb 22E7, anti-IgE, and formyl-methionyl-leucyl-phenylalanine (fMLP); basophil numbers; and total cellular histamine were measured in 26 patients with CIU and 18 healthy control subjects. Twelve patients were classified as having functional anti-FcϵRI and/or anti-IgE autoantibodies on the basis of their serum-evoked histamine release from the basophils of 2 healthy donors. Results: 22E7 and anti-IgE, but not fMLP, released less histamine from basophils of patients with CIU than from those of control subjects. Mean ± SEM maximum histamine release to 22E7 from basophils of control subjects and patients with CIU with and without autoantibodies was 38.5% ± 5.0%, 17.9% ± 6.0% ( P = .01), and 1.0% ± 0.3% ( P P = .04), and 5 ± 1 ( P 6 cells/L, respectively, and similar changes were found in measurements of total cellular histamine. Conclusion: Patients with autoantibodies have both markedly reduced basophil numbers and basophil histamine release to factors acting through FcϵRI, which indicates either a residual pool of functionally distinct basophils or may be a consequence of desensitization of the FcϵRI pathway. (J Allergy Clin Immunol 1998;102:651-8.)

Prostaglandin D2 and histamine release in cold urticaria unaccompanied by evidence of platelet activation

Six patients with acquired primary cold urticaria and six normal control subjects were challenged with a 5-minute immersion of an arm in cold water, at 10 degrees C, to induce cold urticaria. Venous blood draining the arm was sampled before and at 5 and 20 minutes after challenge. Prostaglandin D2 levels in the serum increased significantly after cold challenge but did not correlate with the severity of the urticaria. Significant elevations in histamine after cold challenge tended to be higher in the patients with a low threshold to cold reaction. Two markers of platelet activation, platelet factor 4 and beta-thromboglobulin, remained at basal levels 5 minutes and 20 minutes after challenge.

12-Hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) does not stimulate proliferation of human neonatal keratinocytes.

We have developed an assay to study the effect of drugs on the proliferation of neonatal human skin-derived keratinocytes in vitro. Expanding populations of neonatal keratinocytes were cultured in low concentrations (0.5%) of fetal calf serum for up to 12 d. Growth of the cultures was determined by measurement of DNA using a sensitive fluorimetric assay. Addition of 10(-9)-10(-6) M 12(RS)-hydroxy-5,8,10,14-eicosatetraenoic acid (12(RS)-HETE) neither stimulated keratinocyte proliferation nor enhanced the incorporation of [3H]thymidine. The ability of neonatal keratinocytes in low serum medium to respond to exogenous factors was demonstrated by increased growth in response to a mixture of cholera toxin, hydrocortisone, and epidermal growth factor. Confluent keratinocyte cultures in 10% human AB serum exposed to 12(S)-HETE for 72 h also showed no changes in DNA, [3H]thymidine incorporation, or labeling index. Metabolism of 12(S)-[3H]HETE was greater in cultures containing low concentrations of serum but there was no evidence for the formation of 12,20-dihydroxyeicosatetraenoic acid.

Culture of human dermal fibroblasts in collagen gels: Modulation of interleukin 1-induced prostaglandin E2 synthesis by an extracellular matrix☆

Human dermal fibroblasts, cultured as suspensions in collagen gels and as monolayers, were stimulated with recombinant human interleukin-1 beta (rIL 1 beta) at 72 h, and prostaglandin E2 (PGE2) was assayed 24 h later. Fibroblasts in gels were less responsive to rIL 1 beta than monolayers, PGE2 synthesis increasing from less than 1 ng/microgram DNA without rIL 1 beta to maxima of 11.3 and 32.9 ng/micrograms DNA, with half maximal release occurring at 7.47 and 0.75 pM rIL 1 beta for the gel and monolayer cultures, respectively. Increased PGE2 was first detected 4 h after addition of rIL 1 beta to gels and was inhibited by 10(-5) M indomethacin. The amount of PGE2 synthesized per fibroblast increased with the time the gels had been in culture when stimulated with rIL 1 beta and was proportional to the number of fibroblasts in the gels, but inversely related to the collagen concentration. A common feature of these experiments was significantly greater induction of PGE2 synthesis at higher cell densities in collagen gels. Exogenous 10(-4) M arachidonic acid further increased PGE2 synthesis by rIL 1 beta-stimulated fibroblasts, but the differential in the amount of PGE2 released from fibroblasts at high and low population densities in the gels was maintained. These results are consistent with interleukin 1 (IL 1) stimulating PGE2 synthesis in dermal fibroblasts by increasing cyclooxygenase activity. Furthermore, the results show that dermal fibroblasts have an additional regulatory mechanism, related to the cell population densities or their interactions with an extracellular matrix, to finely modulate the amount of PGE2 synthesized in response to IL 1.

Arachidonate Lipoxygenase Products and Psoriasis

Psoriasis is a common skin disease that, in many cases, appears to be genetically determined. Lesional skin is characterized by epidermal proliferation and inflammatory changes, of which intraepidermal neutrophil infiltration is a consistent finding and one of the earliest abnormalities seen in developing lesions (Chowaniec et al., 1981). Psoriasis may manifest clinically in various forms, of which the chronic, stable, scaly plaque type is the most common. However, the inflammatory changes predominate in some patients, and in generalized pustular psoriasis, an uncommon form of the disease, intraepidermal neutrophil microabscesses are the major pathological feature (Baker and Wilkinson, 1979). These findings suggest that the production of neutrophil chemoattractants by the epidermis may be important in the pathogenesis of psoriasis.