Faculty Bibliography

To evaluate further the interactions of C5a and mast cells in cutaneous inflammation, the ability of human native C5a (nC5a) (10 to 500 ng/ml) and human recombinant C5a (rC5a) (10 ng/ml to 100 ng/ml) to induce histamine release from purified BALB/c cutaneous mast cells (CMC) and peritoneal mast cells (PMC) was analyzed. It was found that nC5a induced histamine release from CMC but not from PMC, with a maximal net release at 250 ng/ml nC5a (22.8 +/- 2.6%). Kinetic experiments demonstrated that nC5a-induced maximal net histamine release occurred 5 min after the presentation of this stimulus (25.8 +/- 6.0%). Using rC5a and CMC, dose-response studies indicated a maximal net release of 7.0 +/- 1.7% at rC5a of 10 ng/ml, and kinetic studies showed a maximal net release at 5 min of incubation (12.9 +/- 1.6%). Release induced by rC5a was calcium-dependent, and peaked at 30 degrees C. These results indicate that functional heterogeneity exists between the CMC and the PMC of BALB/c mice, that C5a is a relevant stimulus for characterization of this heterogeneity, and that CMC from these animals can serve as a convenient in vitro model for the study of human C5a-mast cell interactions. In vivo, injections of nC5a (25-100 ng) and rC5a (25-100 ng) into the skin of BALB/c mice induced an increase in cutaneous vasopermeability, as assessed by the extravasation of intravenously injected 125I-bovine serum albumin. nC5a induced a dose-dependent increase in vasopermeability, whereas alterations induced by rC5a plateaued at 50 ng. The C5a-induced vasopermeability was markedly enhanced in animals that had been previously treated with an inhibitor of serum carboxypeptidase, which converts C5a to the less potent derivative, C5a des Arg. These findings suggest that carboxypeptidase plays an important role in vivo in the modulation of C5a-induced cutaneous inflammation in murine skin

Although the ideal treatment for urticaria is identification and removal of its cause, no underlying cause can be discerned in the majority of instances. The chief clinical problem is the treatment of chronic idiopathic urticaria. H1-receptor antagonists are the major class of therapeutic agents used in the management of chronic idiopathic urticaria. The H1 antagonists have been divided into subgroups based on their chemical structure. The second-generation H1 antagonists now available are particularly advantageous for individuals who must remain alert while working. Terbutaline, a beta-adrenergic agonist, is of occasional benefit as an adjunct therapy in combination with an H1 antagonist. The oral administration of disodium cromoglycate is ineffective in patients with chronic idiopathic urticaria, although a few individuals with urticaria caused by food allergy may respond to this drug. It is best to avoid repeated injections of epinephrine and the systemic administration of corticosteroids. Urticaria has a capricious course: it may respond to the administration of placebos or it may resolve spontaneously. About 50% of the patients with urticaria are free of lesions within 1 year, but 20% continue to have episodes for more than 20 years

The responses of normal skin to ultraviolet (UV) irradiation are an example of inflammation. The chromophores initiating the reaction are unknown. Characteristic clinical findings are erythema, heat, swelling, and pain. Histopathologic changes include epidermal keratinocyte damage with Langerhans cell depletion and dermal edema, endothelial swelling, mast cell degranulation, and cellular infiltration with neutrophils and monocytes. Biochemical changes include release of histamine, cyclo-oxygenase, and lipoxygenase-derived products of arachidonic acid, kinins, and cytokines, probably from a range of epidermal and dermal cell types. These substances very likely assist in mediation of the reaction. The response is more pronounced in young subjects. UVB (280 to 315 nm) and UVA (315 to 400 nm) radiation both produce inflammation, but with marked qualitative and quantitative differences. UVB having more effect on the epidermis, UVA more on the dermis

Systemic sclerosis is characterized by excessive deposition of collagen and other matrix proteins in the skin and internal organs. One hypothesis supports fibroblast stimulation for production of excess amounts of collagen by factors present in the blood or released by cells composing inflammatory tissue infiltrates. Increased numbers of mast cells are present in the involved skin of patients with systemic sclerosis, and histamine has been thought to be a possible mediator of fibrosis in this and other fibrotic conditions. We therefore measured plasma histamine levels in 32 patients with systemic sclerosis and found elevated levels in 18 patients (56%). Elevated plasma histamine levels were more common in patients with diffuse disease (74%), in contrast to limited disease (31%). The degree of clinical activity and the duration of disease could not be correlated with histamine levels

To investigate the functional heterogeneity of mouse mast cells, we extracted and purified cutaneous and peritoneal mast cells from 10- to 18-week-old BALB/c mice and compared their responses to secretagogues. Cutaneous mast cells (CMC) were extracted from mouse ears after digestion with hyaluronidase and collagenase in MEM containing 25% fetal calf serum and purified on a discontinuous Percoll gradient. The histamine content of cells obtained from the 30/40% interface was 1.0 +/- 0.1 pg/cell (mean +/- SE), with a mast-cell purity of 68.6 +/- 4.4% and a viability of greater than 93%. Peritoneal mast cells (PMC) were obtained by lavage with modified Tyrode's buffer followed by purification on 22.5% and 3-9% metrizamide gradients. The histamine content of cells was 12.2 +/- 0.8 pg/cell, with a mast-cell purity of 95.9 +/- 0.6% and a viability of greater than 95%. Histamine release induced by A23187 from CMC peaked at 3.0 microM A23187 (19.1 +/- 4.2%), at 3.0 min (22.3 +/- 2.3%), and at 30 degrees C (17.6 +/- 2.6%). In contrast, histamine release from PMC peaked at 8.0 microM of A23187 (49.4 +/- 12.1%) and at 15.0 min (48.5 +/- 12.2%). Release of histamine from PMC was observed at all the temperatures tested from 22 to 45 degrees C. Histamine release from CMC and PMC induced by A23187 was calcium dependent. Histamine release induced by compound 48/80 from CMC peaked at 0.5 micrograms/ml of compound 48/80 (23.0 +/- 7.4%) and at 5.0 min incubation (16.3 +/- 2.0%), whereas release from PMC peaked at 10.0 micrograms/ml (31.9 +/- 2.6%); release from PMC was similar at all the time points examined (1-15 min). Histamine release induced by substance P (SP) from both CMC and PMC peaked at 5.0 microM (18.8 +/- 6.6% and 12.6 +/- 3.7%, respectively); however, the maximal release from CMC occurred at 3.0 min (18.2 +/- 3.2%) and from PMC at 30.0 min (11.4 +/- 2.0%). SP-induced histamine release from CMC was calcium dependent, whereas release from PMC was only partially inhibited by EDTA. This study demonstrated that functional heterogeneity exists between these two populations of mast cells

BALB/c mice were treated with cimetidine (100 mg/kg) or saline, intraperitoneally, twice daily, from days 0-2 or days 7-9 after sensitization with 0.1%, 2,4,6-trinitro-1-chlorobenzene (TNCB) on day 0. On day 7, the mice were challenged with 1% TNCB to one ear. Ear swelling responses (as an index of sensitization), serum histamine levels, and biopsy specimens of challenged ears were evaluated in groups of cimetidine- or saline-treated mice at 0, 0.5, 1, 1.5, 2, 4, 6, 8, 12, 24, and 48 h after challenge. Additional controls included mice injected with saline or cimetidine and challenged with, but not sensitized to, TNCB (irritant controls). Treatment with cimetidine during the induction but not the elicitation of allergic contact hypersensitivity (ACH) produced a significant enhancement of the response throughout the first 48 h. There was no effect of cimetidine on antigen-presenting cells within the epidermis which might account for this enhancement. Similarly, no difference in mast cell morphology or serum histamine levels between cimetidine- and saline-treated groups was observed. Histologically, the cimetidine-treated animals showed a more intense cellular infiltrate, which was most noticeable at 24 to 48 h, at which time numerous subcorneal and perifollicular neutrophilic abscesses were observed. To further investigate the mechanism of action of cimetidine, mice were injected with cyclophosphamide (150 mg/kg) 2 d prior to sensitization. Mice treated with cyclophosphamide alone or in combination with cimetidine showed no additive or synergistic effect upon the ear swelling response. We conclude that enhancement of ACH by cimetidine is independent of any effect on mast cells or antigen-presenting cells, but may relate to a cimetidine-induced inhibition of the induction of T-suppressor cells at the time of sensitization

Twelve patients with photodermatitis for longer than 3 months' duration were identified: 1 patient with chronic photocontact dermatitis, 1 with persistent photosensitivity following exposure to a systemic medication, 6 with persistent light reactivity, and 4 with actinic reticuloid. There were 10 men and 2 women, ranging in age from 27 to 81 years, with a mean age of 62 years. The duration of the eruption ranged from 6 months to 20 years. Persistence of photosensitivity to quinidine, which is analogous to persistent light reactivity, was documented in 1 patient, and evolution from photocontact dermatitis to actinic reticuloid was observed in 2 others. These data, along with those reported in the literature, indicate that chronic photocontact dermatitis, persistent photosensitivity to systemic agents, persistent light reactivity, photosensitive eczema, and actinic reticuloid should be considered as entities occurring along a continuum, and the term 'chronic actinic dermatitis' is suggested to refer to these entities. Eight (67%) of the 12 patients had skin type VI and 2 others (17%) had skin type V, percentages markedly higher than those of the general patient population, demonstrating that chronic actinic dermatitis is not uncommon among individuals with dark skin

The routine examination of skin biopsy specimens embedded in paraffin and strained with hematoxylin-eosin has failed to allow differentiation of atopic eczema from other types of eczematous dermatitis. The use of 1-micron plastic-embedded sections permits the recognition of infiltrating cell types and blood vessel alterations, thus allowing a refined method to examine cutaneous lesions and permit better definition of cutaneous structures than can be achieved in routinely-processed specimens. Acute vesicular lesions exhibited marked epidermal intercellular edema (spongiosis) and a dermal inflammatory infiltrate of lymphocytes, and activated lymphocytes with normal numbers of mast cells that exhibited various degrees of hypogranulation. Only rare eosinophils, neutrophils, and basophils were noted. Venular alterations included endothelial cell hypertrophy without necrosis. In lichenified plaques there was epidermal hyperplasia with a dermal inflammatory infiltrate that included increased numbers of fully granulated mast cells and increased numbers of lymphocytes and monocyte-macrophages. Alterations of venules included marked endothelial cell hypertrophy and basement membrane thickening. Cutaneous nerves exhibited demyelination and fibrosis. Also, increased numbers of Langerhans' cells have been noted in the epidermis of chronic lesions. Despite the absence of eosinophils, major basic protein has been demonstrated in the dermis by direct immunofluorescence techniques. Studies of lymphocyte subsets have shown increased numbers of CD4+ T lymphocytes