We induced in allergic humans the counterpart of murine experimental T-cell tolerance. T-cell lines from cat-allergic humans were used to map T-cell epitopes for the principal allergen of cat dander, Fel d 1. Two peptides of 27 amino acids each were synthesized to contain the dominant epitopes (ALLERVAX CAT). After a safety trial, we carried out a blinded study of the dose required for efficacy. We randomly divided 95 cat-sensitive patients into placebo, 7.5 micrograms, 75 micrograms, and 750 micrograms groups. Patients received a subcutaneous injection weekly for 4 wk. Before and after treatment, patients were exposed in a room inhabited by live cats and scored by nose and lung symptoms. Baseline nasal and lung scores (+/-SEM) were 6.2 +/- 0.56 and 5.4 +/- 0.73 in the 750 micrograms group; 7.8 +/- 0.53 and 4.7 +/- 0.68 in the placebo group. Six weeks after treatment, scores adjusted for baseline differences were reduced in the 750 micrograms group: -2.3 +/- 4.9 and -2.3 +/- 0.59 compared with -0.84 +/- 0.50 and -0.85 +/- 0.62 in the placebo group. The 75 micrograms group showed intermediate effects and the 7.5 micrograms group no effect. Linear trend analysis indicated a significant dose response effect: p = 0.05 for nose and 0.03 for lung symptoms. Allergic side effects occurred an hour or more after the first 750 micrograms dose in 16 of 24 patients but required little or no treatment with one exception. T-cell reactive treatment peptides safely improved allergic responses to cats.

Slow-reacting substance of anaphylaxis (composed of leukotrienes C, D, and E) is released in vitro by the interaction of antigen and IgE antibody on human mast cells and basophils. When we challenged ragweed-sensitive patients intranasally with pollen grains, their clinical response was significantly correlated with the release of the peptide leukotrienes (P less than 0.001). Nonallergic subjects had neither symptoms nor leukotriene release. The leukotrienes were released in a dose-dependent fashion, with a peak mean level of 827 +/- 234 pg per 0.1 ml of a 10-ml nasal wash. High-performance liquid chromatography revealed the presence of leukotrienes C, D, and E, suggesting that nasal cells or fluids had the ability to degrade leukotriene C enzymatically. The in vivo release of these potent inflammatory mediators after exposure to pollen suggests that leukotrienes may have an important role in human allergic reactions.

Lipid bodies are non-membrane-bound, lipid-rich cytoplasmic inclusions that occur in many mammalian cell types. Because lipid bodies are more prominent in cells associated with inflammation and are repositories of arachidonylphospholipids, a role for lipid bodies in the oxidative metabolism of arachidonic acid to form eicosanoids has been suggested. To evaluate further whether lipid bodies, in addition to serving as non-membranous sources of substrate arachidonate, are involved in eicosanoid formation, we used cells isolated from human lung to investigate the intracellular localization of prostaglandin endoperoxide (PGH) synthase (cyclmxygenase), the key initial, rate-limiting enzyme in the formation of prostaglandins and thromboxanes. Isolated lung cells containing a mixture of mast cells, alveolar macrophages, Type 11 alveolar pneumocytes, and neutrophils from short-term cultures were fted in suspension in a dilute aldehyde mixture, post-fixed in osmium tetroxide, stained en bloc with uranyl acetate, dehydrated in a graded series of alcohols, and embedded in Epon. A post-embedding immunogold procedure was used with a primary PGH synthase monoclonal antibody and 20-nm gold-conjugated sec-

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A B S T R A C T Although mediator release from mast cells and basophils plays a central role in the pathogenesis of human allergic disease, biochemical studies have been restricted to rat peritoneal mast cells and basophilic leukemia cells because they could be easily purified. We have used two new techniques of cell separation to purify human lung mast cells to 98% homogeneity. Lung cell suspensions were obtained by dispersion of chopped lung tissue with proteolytic enzymes. Mast cells were then purified from the suspensions by countercurrent centrifugal elutriation and affinity chromatography. The purified mast cells released both histamine and slow-reacting substance of anaphylaxis (SRS-A) (leukotriene C and D) during stimulation with goat anti-human IgE antibody. Moreover, these preparations were able to generate significant quantities of SRS-A (32±7X 10-'7 LTD moleequivalents/mast cell) at all stages of purification, indicating that a secondary cell is not necessary for the antigen-induced release of SRS.

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While capable of inhibiting histamine and LTC(4) release by human basophils, desloratadine is more effective at targeting the signals regulating IL-4 and IL-13 generation in these cells. This inhibitory effect on cytokine generation provides additional evidence that this antihistamine exerts anti-inflammatory properties.

We used a morphometric and autoradiographic approach to analyze changes in specific cytoplasmic granules and cytoplasmic lipid bodies associated with human lung mast cell degranulation. Mast cells were dissociated from lung tissue by enzymatic digestion and were then enriched to purities of up to 99% by countercurrent centrifugation elutriation and recovery from columns containing specific antigen bound to Sepharose 6 MB. Degranulation was induced by goat anti-lgE. At various intervals after stimulation, parallel aliquots of cells were recovered for determination of histamine release or were fixed for transmission electron microscopy. We found that lipid bodies, electron-dense structures that lack unit membranes, were present in both control and stimulated mast cells. Autoradiographic analysis showed that lipid bodies represented the major repository of 3H-label derived from [3H]arachidonic acid taken up from the external milieu. By contrast, the specific cytoplasmic granules contained no detectable 3H-label. In addition, lipid bodies occurred in intimate association with degranulation channels during mast cell activation, but the total volume of lipid bodies did not change during the 20 min after stimulation with anti-lgE. This result stands in striking contrast to the behavior of specific cytoplasmic granules, the great majority of which (77% according to aggregate volume) exhibited ultrastructural alterations during the first 20 min of mast cell activation.These observations establish that mast cell cytoplasmic granules and cytoplasmic lipid bodies are distinct organelles that differ in ultrastructure, biochemistry, and behavior during mast cell activation.