Number Of Mast Cells In Skin Research Articles

Protective role of protease-activated receptor-2 in anaphylaxis model mice.

Anaphylaxis is a severe life-threatening hypersensitivity reaction induced by mast cell degranulation. Among the various mediators of mast cells, little is known about the role of tryptase. Therefore, we aimed to elucidate the role of protease-activating receptor-2 (PAR-2), a receptor activated by tryptase, in murine anaphylactic models using PAR-2-deficient mice and newly generated tryptase-deficient mice. Anaphylaxis was induced by IgE-dependent and IgE-independent mast cell degranulation in mice. PAR-2 deficiency exacerbated the decrease in body temperature and hypotension during anaphylaxis; however, the number of skin mast cells, degree of mast cell degranulation, and systemic and local vascular hyperpermeability were comparable in PAR-2 knockout and wild-type mice. Nitric oxide, which is produced by endothelial nitric oxide synthase (eNOS), is an indispensable vasodilator in anaphylaxis. In the lungs of anaphylactic mice, PAR-2 deficiency promoted eNOS expression and phosphorylation, suggesting a protective effect of PAR-2 against anaphylaxis by downregulating eNOS activation and expression. Based on the hypothesis that the ligand for PAR-2 in anaphylaxis is mast cell tryptase, tryptase-deficient mice were generated using CRISPR-Cas9. In wild-type mice, the PAR-2 antagonist exacerbated the body temperature drop due to anaphylaxis; however, the effect of the PAR-2 antagonist was abolished in tryptase-deficient mice. These results suggest that tryptase is a possible ligand of PAR-2 in anaphylaxis and that the tryptase/PAR-2 pathway attenuates the anaphylactic response in mice.

Contributions of Diet and Age to Ulcerative Dermatitis in Female C57BL/6J Mice.

C57BL/6J (B6) mice are commonly affected by ulcerative dermatitis (UD), a disease of unknown etiology with poor response to treatment. To study the possible role of diet in UD, we compared skin changes in B6 female mice fed a high-fat diet with those of mice fed a control diet. In addition, skin samples from mice with no, mild, moderate, and severe clinical signs of UD were examined by light and transmission electron microscopy (TEM). Mice fed a high-fat diet for 2 mo had more skin mast cell degranulation than did mice fed the control diet for the same period. Regardless of diet, older mice had more skin mast cells and more of these cells were degranulating as compared with younger mice. Microscopic changes in very early lesions were characterized by an increase in dermal mast cells and degranulation with focal areas of epidermal hyperplasia with or without hyperkeratosis. As the condition progressed, a mixed but predominantly neutrophilic inflammatory cell infiltrate appeared in the dermis, with or without epidermal erosion and scab formation. TEM showed that dermal mast cell membranes had disrupted and released of large number of electron dense granules, whereas degranulated mast cells were filled with isolated and coalescing empty spaces due to fusion of granule membranes. Ulceration appeared to occur very quickly, probably as result of intense scratching due to the pruritogenic properties of the histamine released from mast cell granules. This study showed a direct correlation between dietary fat and skin mast cell degranulation in female B6 mice. In addition, the number of skin mast cells and degranulation rates was higher in older mice. Treatments directed at preventing mast cell degranulation may result in better outcomes when applied early in UD cases. As noted previously in studies using caloric restriction, lower fat content in rodent diets may help prevent UD.

Mast cell deficiency attenuates acupuncture analgesia for mechanical pain using c-kit gene mutant rats.

BackgroundAcupuncture therapy plays a pivotal role in pain relief, and increasing evidence demonstrates that mast cells (MCs) may mediate acupuncture analgesia. The present study aims to investigate the role of MCs in acupuncture analgesia using c-kit gene mutant–induced MC-deficient rats.Materials and methodsWsRC-Ws/Ws rats and their wild-type (WT) littermates (WsRC-+/+) were used. The number of MCs in skin of ST36 area was compared in two rats after immunofluorescence labeling. Mechanical withdrawal latency (MWL), mechanical withdrawal threshold (MWT), and thermal withdrawal latency (TWL) were measured on bilateral plantar for pain threshold evaluation before and after each stimulus. Acupuncture- and moxibustion-like stimuli (43°C, 46°C heat, 1 mA electroacupuncture [EA], 3 mA EA, and manual acupuncture [MA]) were applied randomly on different days.ResultsFewer MCs were observed in the skin of ST36 in mutant rats compared to WT rats (P<0.001). For pain thresholds, MWL and MWT were higher in WsRC-Ws/Ws compared to WsRC-+/+ on bilateral paws (P<0.05), but TWL was not different between the two rats (P>0.05). Bilateral MWL and MWT in WsRC-+/+ rats increased significantly after each stimulus compared to baseline (P<0.01, P<0.001). In WsRC-Ws/Ws rats, only noxious stimuli could produce anti-nociceptive effects for mechanical pain (46°C, 3 mA EA, MA) (P<0.01, P<0.001). Additionally, the net increases in MWL and MWT induced by most stimuli were greater in WT than in mutant rats (P<0.05). For thermal nociception, either high- or low-intensity stimuli could significantly augment TWL in two rats (P<0.001), and the net increases of TWL evoked by most stimuli were to the same extent in two genetic variants.ConclusionMCs influence the basic mechanical but not thermal pain threshold. MCs participate in acupuncture analgesia in mechanical but not in thermal nociception, in that MC deficiency may attenuate the mechanical analgesia evoked by high-intensity stimuli and eliminate analgesia provoked by low-intensity stimuli.

Ablation of human skin mast cells in situ by lysosomotropic agents.

Mast cells are known to have a detrimental impact on numerous types of inflammatory skin diseases such as contact dermatitis, atopic eczema and cutaneous mastocytosis. Regimens that dampen skin mast cell-mediated activities can thus offer an attractive therapeutic option under such circumstances. As mast cells are known to secrete a large array of potentially pathogenic compounds, both from preformed stores in secretory lysosomes (granules) and after de novo synthesis, mere inhibition of degranulation or interference with individual mast cell mediators may not be sufficient to provide an effective blockade of harmful mast cell activities. An alternative strategy may therefore be to locally reduce skin mast cell numbers. Here, we explored the possibility of using lysosomotropic agents for this purpose, appreciating the fact that mast cell granules contain bioactive compounds prone to trigger apoptosis if released into the cytosolic compartment. Based on this principle, we show that incubation of human skin punch biopsies with the lysosomotropic agents siramesine or Leu-Leu methyl ester preferably ablated the mast cell population, without causing any gross adverse effects on the skin morphology. Subsequent analysis revealed that mast cells treated with lysosomotropic agents predominantly underwent apoptotic rather than necrotic cell death. In summary, this study raises the possibility of using lysosomotropic agents as a novel approach to targeting deleterious mast cell populations in cutaneous mastocytosis and other skin disorders negatively influenced by mast cells.

(401) Mast cell stabilizer (ketotifen): implications for the pathophysiology of Fibromyalgia

Emerging data suggest that fibromyalgia (FM) is a neuro-immunologic disorder. Compared to healthy controls, FM patients have greater number of skin mast cells - potent inflammatory cells capable of releasing pro-inflammatory and neuro-sensitisizing molecules. Whether or not these cells are involved in the pathogenesis of FM is unclear. We designed a randomized controlled trial to determine the effects of a mast cell stabilizer (ketotifen) on FM symptoms. Ketotifen is commonly used to treat two mast cell-mediated conditions, bronchial asthma and allergic skin disorders. Fifty-one FM subjects were randomized to daily oral ketotifen 2 mg BID (n=24) for 8 weeks or placebo (N=27). Those with atopic dermatitis, chronic urticaria, or taking anti-allergy drugs were excluded. Demographics of the 51 FM subjects: mean age= 51.2 (SD 8.4) years; female=88%; whites= 88%; ≥high school graduates=71%; concomitant opiates=22%; PHQ-8 depression=13.5 (5.4); experimental pressure pain sensitivity (range 0-20) = 10.0 (0.4); weekly average pain intensity (ActiWatch Pain Monitor) = 6.4 (1.1); and revised FIQ (global FM symptom severity) =66.8 (14.0). We found no statistically significant treatment group differences in the baseline to week 8 changes of our two primary measures: weekly average pain intensity [ketotifen -1.3 (1.9) vs. placebo -1.5 (1.9), p=0.7]; and revised FIQ [-12.1 (19.5) vs. -12.2 (18.1), p=0.9]. Further, no secondary outcome measures (BPI pain intensity, and experimental pressure pain sensitivity) reached statistical significance (p>0.5). Our results did not differ in the intent-to-treat and completer analyses. Three subjects in the ketotifen group and 2 in the placebo group discontinued the study due to study protocol violations. Other than transient sedation [6 (28.6%) vs. 1 (4.0%)], oral ketotifen was well tolerated. In conclusion, oral ketotifen was not associated with improvement of FM symptoms. Importantly, skin mast cells are not major contributor in the pathogenesis of FM. Funded by NIAMS (NIH).

Basophils help establish protective immunity induced by irradiated larval vaccination for filariasis

Basophils are increasingly recognized as playing important roles in the immune response toward helminths. In this study, we evaluated the role of basophils in vaccine-mediated protection against filariae, tissue-invasive parasitic nematodes responsible for diseases such as elephantiasis and river blindness. Protective immunity and immunological responses were assessed in BALB/c mice vaccinated with irradiated L3 stage larvae and depleted of basophils with weekly injections of anti-CD200R3 antibody. Depletion of basophils after administration of the vaccination regimen but before challenge infection did not alter protective immunity. In contrast, basophil depletion initiated prior to vaccination and continued after challenge infection significantly attenuated the protective effect conferred by vaccination. Vaccine-induced cellular immune responses to parasite antigen were substantially decreased in basophil-depleted mice, with significant decreases in CD4+ T-cell production of IL-4, IL-5, IL-10, and IFN-γ. Interestingly, skin mast cell numbers, which increased significantly after vaccination with irradiated L3 larvae, were unchanged after vaccination in basophil-depleted mice. These findings demonstrate that basophils help establish the immune responses responsible for irradiated L3 vaccine protection.

Chronic psychological stress exaggerates the compound 48/80-induced scratching behavior of mice

Although accumulating clinical evidence has shown that psychological stress worsens cutaneous symptoms by exaggerating scratching behavior, how the stress affects the scratching is unclear. Therefore, we herein investigated this using an animal model of scratching. Male BALB/c mice were exposed to 1h water avoidance stress (WAS) for ten consecutive days. Twenty-four hours after the last stress session, the mice were injected into the back of the neck with a condensation product of N-methyl-p- methoxyphenethylamine with formaldehyde (compound 48/80), and their scratching behavior was then observed for 120min. Mast cell number in the skin and histamine and corticosterone levels in the plasma were examined. The scratching number was significantly higher in the chronic WAS group than in the control group. Both mast cell number in the skin and the peak histamine in the plasma after the compound 48/80 injection were also significantly higher in the chronic WAS group in comparison to the control group. Chronic WAS delayed the peak corticosterone plasma response to the compound 48/40 injection. These findings indicate that chronic WAS exacerbates the compound 48/80-induced scratching behavior of mice. Both the increased number of skin mast cells and delayed glucocorticoid reaction may be related to this exacerbation.

Kit ligand cytoplasmic domain is essential for basolateral sorting in vivo and has roles in spermatogenesis and hematopoiesis

Juxtamembrane signaling via the membrane growth factor KitL is critical for Kit mediated functions. KitL has a conserved cytoplasmic domain and has been shown to possess a monomeric leucine-dependent basolateral targeting signal. To investigate the consequences in vivo of impaired basolateral KitL targeting in polarized epithelial cells, we have mutated this critical leucine to alanine using a knock-in strategy. KitL(L263A/L263A) mutant mice are pigmented normally and steady-state hematopoiesis is unaffected although peritoneal and skin mast cell numbers are significantly increased. KitL localization is affected in the Sertoli cells of the KitL(L263A/L263A) testis and testis size is reduced in these mice due to aberrant spermatogonial proliferation. Furthermore, the effect of the KitL L263A mutation on the testicular phenotype is dosage dependent. The tubules of hemizygous KitL(L263A/Sl) mice completely lack germ cells in contrast to the weaker testicular phenotype of KitL(L263A/L263A) mice. The onset of the testis phenotype coincides with the formation of tight junctions between Sertoli cells during postnatal development. Thus, the altered sorting of KitL is dispensable for hematopoietic and melanogenic lineages, yet is crucial in the testicular environment, where the basal membranes of adjacent polarized Sertoli cells form a niche for the proliferating spermatogonia.

Role of TRPV3 in immune response to development of dermatitis

BackgroundRecently, it has been reported that the Gly573Ser substitution of transient receptor potential V3 (TRPV3) leads to increased ion-channel activity in keratinocytes. Our previous studies have indicated that the spontaneous hairless and dermatitis phenotypes of DS-Nh mice, which were newly established as an animal model of atopic dermatitis (AD), are caused by TRPV3Gly573Ser. Although this substitution causes hairlessness in several kinds of rodents, in our investigations, dermatitis developed in only a few animals. Here, we generated NC/Nga-Nh mice to elucidate the role of TRPV3Gly573Ser in NC/Nga mice, which is one of the most studied animal models of AD.MethodsTo establish and validate the new AD animal model, NC/Nga-Nh mice were generated using NC/Nga and DS-Nh mice, and their clinical features were compared. Next, T-cell receptor (TCR) Vβ usage in splenocytes, evaluation of bacterial colonization, and serological and histological analyses were carried out. Finally, repeated-hapten-application dermatitis was induced in these mice.ResultsNC/Nga-Nh mice did not develop spontaneous dermatitis, whereas DS-Nh mice displayed this phenotype when maintained under the same conditions. Serological analysis indicated that there really was a phenotypic difference between these mice, and TCR repertoire analysis indicated that TCRVβ haplotypes played an important role in the development of dermatitis. Artificial dermatitis developed in DS and NC/Nga-Nh mice, but not in DS-Nh and NC/Nga mice. Histological and serological analyses indicated that mouse strains were listed in descending order of number of skin mast cells: DS-Nh > DS ≈ NC/Nga-Nh > NC/Nga, and serum IgE levels were increased after 2,4,6 trinitrochlorobenzene application in these mice. Serum IgE level in DS-Nh mice was lower than that mesured in other strains.ConclusionOur results confirm the contribution of the TRPV3Gly573Ser gene to the development of repeated hapten dermatitis, but not spontaneous dermatitis in NC/Nga mice.

Suppression of Allergic Inflammatory Response in the Skin of Alloxan-Diabetic Rats: Relationship with Reduced Local Mast Cell Numbers

Background: Diabetic patients are refractory to allergic inflammatory diseases. In this study, the influence of alloxan-induced diabetes on allergic skin inflammation was investigated. Methods: Diabetes was induced by intravenous injection of alloxan into male Wistar rats, and the analyses were performed 21 days later. Animals were actively sensitized with a mixture of aluminium hydroxide plus ovalbumin and challenged intradermally with ovalbumin on day 14. Results: Diabetic sensitized rats exhibited a less pronounced antigen-induced protein extravasation in the dorsal skin when compared with normal animals. Also, fragments of the dorsal subcutaneous tissue from diabetic sensitized rats showed a reduction in histamine release after stimulation with antigen in vitrowhen compared with fragments obtained from nondiabetic sensitized rats. Optical microscopy analysis revealed that the dorsal skin of diabetic rats showed a marked reduction in dermis thickness, as compared with that seen in normal animals. A significant decrease in the number of skin mast cells was also noted, a phenomenon that paralleled with the reduction in the expression of extracellular matrix components laminin, fibronectin and collagen. Administration of insulin into diabetic rats restored basal mast cell numbers as well as the levels of laminin, fibronectin and collagen. Conclusions: Our findings show that alloxan diabetes induces downregulation of the skin allergic inflammatory response in rats, and this was correlated with reduction in local mast cell numbers and expression of extracellular matrix components. Lastly, these alterations were reversed with insulin treatment.

Differential Effects of Doses and Forms of Dietary Selenium on Immune Cell Numbers in the Skin of Ultraviolet-irradiated and Unirradiated Mice

The effect of three different doses of dietary L-selenomethionine (SM) and sodium selenite (SS) on skin selenium (Se) content, glutathione peroxidase (GPx) activity, Langerhans cell (LC) and mast cell numbers in ultraviolet radiation-B (UVB)-irradiated and unirradiated C3H/HeN mice was determined. After weaning, groups of mice were given Se-deficient, Se-adequate, or Se-high diets. Six weeks later, some animals in each group were exposed to a single UVB dose (acute), while others were exposed three times weekly for the following 40 weeks (chronic). The skin Se content and GPx activity increased in all the Se-supplemented groups, and the latter was not altered by UVB exposure. Generally, the Se-containing diets caused an increase in LC numbers at 6 weeks and a further rise at 40 weeks, but did not prevent the loss induced by acute or chronic UVB radiation. Skin mast cell numbers were highest in animals fed the Se-deficient diet after 6 and 40 weeks. Acute and chronic UVB radiation decreased the mast cell number and dietary Se did not prevent the reduction. While the present study shows that Se plays an important role in governing the number of LCs and mast cells in the skin, no protective effect against the immunomodulating properties of UVB radiation on these cell types was observed. However, this conclusion may only apply to the experimental conditions chosen, and additional studies at different Se dosages and reduced intensities of chronic UVB exposure are required to confirm the results.

Effects of Gamma Radiation on FcεRI and TLR-Mediated Mast Cell Activation

Ionizing gamma radiation has several therapeutic indications including bone marrow transplantation and tumor ablation. Among immune cells, susceptibility of lymphocytes to gamma radiation is well known. However, there is little information on the effects of gamma radiation on mast cells, which are important in both innate and acquired immunity. Previous studies have suggested that mast cells may release histamine in response to high doses of gamma radiation, whereas other reports suggest that mast cells are relatively radioresistant. No strong link has been established between gamma radiation and its effect on mast cell survival and activation. We examined both human and murine mast cell survival and activation, including mechanisms related to innate and acquired immune responses following gamma radiation. Data revealed that human and murine mast cells were resistant to gamma radiation-induced cytotoxicity and, importantly, that irradiation did not directly induce beta-hexosaminidase release. Instead, a transient attenuation of IgE-mediated beta-hexosaminidase release and cytokine production was observed which appeared to be the result of reactive oxygen species formation after irradiation. Mast cells retained the ability to phagocytose Escherichia coli particles and respond to TLR ligands as measured by cytokine production after irradiation. In vivo, there was no decrease in mast cell numbers in skin of irradiated mice. Additionally, mast cells retained the ability to respond to Ag in vivo as measured by passive cutaneous anaphylaxis in mice after irradiation. Mast cells are thus resistant to the cytotoxic effects and alterations in function after irradiation and, despite a transient inhibition, ultimately respond to innate and acquired immune activation signals.

Search for evidence of a Th2 profile in HIV+ patients.

Hypersensitivity dermatoses are common in human immunodeficiency virus-positive (HIV+) patients, particularly as the disease progresses. Studies have shown that a switch to T-helper 2 (Th2) might represent a turning point in HIV. This study investigated whether increases in the number of skin mast cells, immunoglobulin E (IgE) serum levels, and eosinophilia, involved in the Th2 response in allergic disease, might also be present in HIV+ patients. If so, these alterations might explain one of the mechanisms of skin hypersensitivity in these patients. Forty-five skin biopsies from the normal skin of the upper arm of HIV+ patients and 15 controls were included in the study. HIV+ individuals were classified into three equal categories according to their immunologic status: Category I (< 200/microL), Category II (200-499/microL), and Category III (> 500/microL). Anti-tryptase antibody was employed in tissue sections to show mast cells; IgE serum levels and eosinophils in peripheral blood count were investigated; delayed-type hypersensitivity (DTH) skin tests (candidin, trichophytin, and PPD 2U) were evaluated. Normal cutaneous mast cell and eosinophil counts were the same in all categories and in the control group, but increased IgE levels (P < 0. 01) and DTH skin test anergy (P < 0.006) were observed among acquired immunodeficiency syndrome (AIDS) patients. The density of skin mast cells in HIV infection was not modified in the course of the disease. Mast cells do not seem to be primarily responsible for triggering hypersensitivity dermatoses among AIDS patients, although data in support of the Th2 response, as seen in increased IgE serum levels and DTH anergy, are present.

Abundant Expression of Transcription Factor GATA-2 in Proliferating But Not in Differentiated Mast Cells in Tissues of Mice: Demonstration by In Situ Hybridization

Although GATA-binding transcription factors (GATA-1 and GATA-2) are strongly expressed in cultured mast cells (CMCs), their expression in mast cells within tissues has not been reported. We examined the expression of GATA-1 and GATA-2 in skin tissues of mice using Northern blot analysis and in situ hybridization. mRNA for GATA-2 but not for GATA-1 was expressed in skin mast cells of WB-+/+ embryos between days 15 and 17 postcoitum (pc). The expression was downregulated on and after day 18 pc. Skin mast cells did not express GATA-2 after birth either. When the number of skin mast cells was compared with the number of GATA-2 mRNA-expressing cells, GATA-2 mRNA appeared to be expressed by mast cells only when the number was increasing. When the mRNA expression of high-affinity IgE receptor beta-subunit and mast cell carboxypeptidase A was used as differentiation markers, the expression of these mRNAs continued even after the downregulation of GATA-2 expression. To clarify the relationship of the proliferation and GATA-2 expression, proliferating CMCs derived from WBB6F1-+/+ mice were transplanted into the peritoneal cavity of mast cell-deficient WBB6F1-W/Wv mice. The CMCs stopped both the proliferation and GATA-2 expression after the transplantation, suggesting the association of these two parameters in mast cells within tissues of mice.

Immunosuppression and feeding success of Ixodes ricinus nymphs on BALB/c mice

The effect of repeated infestations of Ixodes ricinus (L.) nymphs on BALB/c mice was studied. Four successive infectations resulted in an increase of tick feeding success. Tick yield and mean engorged weight increased and the length of the feeding period was reduced significantly (P < 0.05-0.01). The increase of specific anti-tick antibodies was not significant (P > 0.05). The blastogenic response of spleen lymphocytes to T-cell mitogens (Con A and PHA-P) was unimpaired or slightly enhanced, whereas the response to B-cell activators (LPS and PWM) was suppressed, as was the total antibody generation in vitro. The numbers of mast cells in murine skin at the tick attachment sites slightly decreased during the third infestation. The suppression of B-cell competence and of antibody generation, together with decrease of skin mast cell numbers in tick attachment sits, are considered to be responsible for enhancement of tick feeding success.

Mast Cell Number in the Skin of Heterozygotes Reflects the Molecular Nature of c-kit Mutation

AbstractThe W locus of mice encodes the c-kit receptor tyrosine kinase. Heterozygous WJic/+ and Wn/+ mice and homozygous Wf/Wf mice were similar in appearance; all of them have large depigmented areas lacking any well-defined pattern. The WJic, Wn, and Wf mutant alleles were characterized and their molecular nature was correlated with the mast cell differentiation in the skin and the biologic features of cultured mast cell (CMC). All WJic, Wn, and Wf were point mutations at the tyrosine kinase domain, and c-kit mRNA was normally transcribed from all of them. The mature 145-Kd form of the c-kit protein was produced from the WJic and Wf alleles, but not from the Wn allele. c-kit proteins produced by the WJic or Wf allele were expressed on the surface of CMCs, but those of the Wn allele were not. When double heterozygous mice were produced between W and WJic and between W and Wn, both W/WJic and W/Wn mice lacked skin mast cells. W/WJic CMCs and W/Wn CMCs did not survive in the coculture with fibroblasts. W/WJic CMCs normally attached to fibroblasts, but W/Wn CMCs did not. The defect of W/Wn CMCs in the attachment was attributed to the deficient extracellular expression of the c-kit protein. The number of skin mast cells was compared among WJic/+, Wn/+, Wf/+, and Wf/Wf mice. Mast cells decreased in WJic/+ and Wf/Wf mice, but not in Wn/+ and Wf/+ mice. Although the Wn was a point mutation at the kinase domain, the biologic effect of the Wn was comparable with that of the W mutant allele, which produces truncated c-kit protein without the transmembrane domain. The weak phenotype of Wn/+ mice may be explained by the deficient extracellular expression of c-kit proteins produced by the Wn allele. When WJic/WJic, Wn/Wn, and Wf/Wf CMCs were stimulated by the recombinant c-kit ligand, autophosphorylation activity was observed only in Wf/Wf CMCs. This result was consistent with the weak biologic effect of the W mutant allele.

Mast cell number in the skin of heterozygotes reflects the molecular nature of c-kit mutation

The W locus of mice encodes the c-kit receptor tyrosine kinase. Heterozygous WJic/+ and Wn/+ mice and homozygous Wf/Wf mice were similar in appearance; all of them have large depigmented areas lacking any well-defined pattern. The WJic, Wn, and Wf mutant alleles were characterized and their molecular nature was correlated with the mast cell differentiation in the skin and the biologic features of cultured mast cell (CMC). All WJic, Wn, and Wf were point mutations at the tyrosine kinase domain, and c-kit mRNA was normally transcribed from all of them. The mature 145-Kd form of the c-kit protein was produced from the WJic and Wf alleles, but not from the Wn allele. c-kit proteins produced by the WJic or Wf allele were expressed on the surface of CMCs, but those of the Wn allele were not. When double heterozygous mice were produced between W and WJic and between W and Wn, both W/WJic and W/Wn mice lacked skin mast cells. W/WJic CMCs and W/Wn CMCs did not survive in the coculture with fibroblasts. W/WJic CMCs normally attached to fibroblasts, but W/Wn CMCs did not. The defect of W/Wn CMCs in the attachment was attributed to the deficient extracellular expression of the c-kit protein. The number of skin mast cells was compared among WJic/+, Wn/+, Wf/+, and Wf/Wf mice. Mast cells decreased in WJic/+ and Wf/Wf mice, but not in Wn/+ and Wf/+ mice. Although the Wn was a point mutation at the kinase domain, the biologic effect of the Wn was comparable with that of the W mutant allele, which produces truncated c-kit protein without the transmembrane domain. The weak phenotype of Wn/+ mice may be explained by the deficient extracellular expression of c-kit proteins produced by the Wn allele. When WJic/WJic, Wn/Wn, and Wf/Wf CMCs were stimulated by the recombinant c-kit ligand, autophosphorylation activity was observed only in Wf/Wf CMCs. This result was consistent with the weak biologic effect of the Wf mutant allele.

A survey of the number and distribution of mast cells in the skin of patients with mast cell disorders

It has been suggested that patients who present with episodes of unexplained anaphytaxis (UEA) or unexplained flushing (UEF) have systemic mastocytosis (SM), a proposal believed to be supported by the presence of excess mast cell (MC) numbers in the skin of these individuals. To examine this hypothesis, we determined the number and distribution of MCs in the skin of nine normal subjects, nine patients with UEA/UEF, six patients with urticaria pigmentosa (UP), and 14 patients with SM. Skin biopsy specimens of normal subjects contained 38.4 ± 4 ( x ± SEM) MCs per square millimeter. Biopsy specimens of patients with UEA/UEF contained 71.8 ± 13 MCs per square millimeter. Although the numbers were significantly different from numbers in skin of normal subjects ( p < 0.05), similar modest increases in MC numbers are observed in a number of skin conditions. In marked contrast, lesional biopsy specimens of patients with UP contained 596.5 ± 278 MCs per square millimeter ( p < 0.05, n = 6, compared to MC numbers in the skin of normal subjects), and patients with SM had 720.6 ± 176 MCs per square millimeter in lesional skin ( p < 0.01, n = 12, compared to normal skin). Patients with UP or SM also had increased MC numbers in nonlesional skin compared to normal skin (168.0 MCs per square millimeter, p < 0.05, n = 5, and 184.4 MCs per square millimeter, p < 0.01, n = 10, respectively). Analysis of the relationship between MCs and blood vessels (BV) suggested that MCs in patients with mastocytosis first increase around BVs and later appear in tissues distant from BVs. Patients with UEA/UEF had an average plasma histamine level of 246.3 ± 51 pg/ml, not significantly different from the average plasma histamine level in normal subjects (262.0 ± 19, n = 76). Patients with UP and SM had plasma histamine levels of 402.5 ± 176 pg/ml and 2032.9 ± 491 pg/ml, respectively, both significantly different ( p < 0.01) from normal subjects. In conclusion, although modest increases (twofold to threefold) in MC numbers are observed in the skin of some patients with UEA and UEF, patients with SM have, on average, a 15-fold to twentyfold increase in MC numbers. Rare exceptions to this observation suggest a need to correlate the gross skin examination with skin MC numbers and to diagnose SM by appropriate criteria.

Mast cells in the initial stages of psoriasis.

Mast cells were counted in 122 patients with psoriasis and 80 healthy volunteers, at different times after scratch from 30 min up to 14 days. Koebner's phenomenon was induced in 74% of patients with active disease (63/85) and in 37.5% with stationary psoriasis (6/16). Mast cells were enumerated also in the skin of ten healthy controls, and their number on the inner aspect of the arm was found to range from 16 to 21 (mean, 17.6 +/- 1.65). Scarification increased the number of skin mast cells both in psoriatics and normal controls. The significant difference was noticed from the 4th day on after scratch, reaching a peak at days 14, simultaneously with the appearance of Koebner's phenomenon. In mature psoriatic lesions the number of mast cells was significantly lower than in newly formed psoriatic lesions, and it decreased progressively with effective anthralin treatment. It is concluded that mast cells play a role in skin response to trauma. In contrast to normal wound healing, their number is steadily increasing at the time of formation of the earliest psoriatic lesions.

Skin mast cells in polycythaemia vera relationship to the pathogenesis and treatment of pruritus

We have measured skin mast cell numbers, circulating basophils and whole blood histamine in 13 patients with polycythaemia vera. Itching was present in nine cases and correlated well with the numbers of skin mast cells but not with circulating basophils or whole blood histamine. Immediate relief of pruritus was achieved with aspirin, and myelosuppressive therapy was useful for long-term control of symptoms. Neither histamine (H1 or H2) antagonists nor iron replacement therapy were effective forms of treatment. The findings suggest that mast cell prostaglandins are an important factor in the pathogenesis of pruritus and that local vascular responses may trigger mast cell degranulation.