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From the Department of Pathology, Graduate School of Frontier Bioscience and Medical School, Osaka University, Osaka, Japan
| Abstract |
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Functions of skin mast cells have been investigated using (WB x C57BL/6)F1 (WBB6F1)-KitW/KitW-v mice.19 Intact WBB6F1-KitW/KitW-v mice were compared with rescued WBB6F1-KitW/KitW-v mice that had received the transplantation of cultured mast cells (CMCs) derived from WBB6F1-+/+ mice. Wershil and colleagues20 demonstrated that mast cells were essential for IgE-dependent immediate hypersensitivity reaction. The IgE-dependent extravasation of fibrinogen did not occur in the skin of intact WBB6F1-KitW/KitW-v mice but did occur in the skin of WBB6F1-KitW/KitW-v mice whose mast cell depletion was rescued by the prior subcutaneous injection of WBB6F1-+/+ CMCs. In contrast to the case of the IgE-dependent immediate hypersensitivity reaction, the presence of mast cells was not essential for neutrophil infiltration induced by phorbol 12-myristate 13-acetate.21 However, the presence of mast cells augmented the neutrophil infiltration. Cutaneous eosinophil infiltration induced by substance P (SP) was examined by Matsuda and colleagues.22 They showed that SP-induced eosinophil infiltration was dependent on the presence of mast cells using air-bleb assay. Yano and colleagues23 injected SP into the ear skin of mice and found the requirement of mast cells for augmentation of SP-induced granulocyte infiltration. In these experiments, a granulocyte infiltration of low level was observed in the skin of intact WBB6F1-KitW/KitW-v mice, but the prior injection of +/+ CMCs significantly augmented the infiltration.
Because the skin of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice contains one third of mast cells than that of WBB6F1-+/+ mice, we attempted to investigate the function of the decreased but appreciable number of mast cells in the skin of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. The SP-induced eosinophil infiltration was examined in the skin tissue of intact WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice using air-bleb assay. Unexpectedly, we found that the air-bleb membranes formed in the back of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice contained no mast cells. Histological study revealed that the air-bleb membrane was composed of the subcutaneous connective tissue. Mast cells were present in the dermis but not in the subcutaneous connective tissue of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. The intact WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice showed impaired SP-induced eosinophil infiltration. Moreover, the prior injection of WBB6F1-+/+ CMCs into the subcutaneous connective tissue of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice did not increase the level of the SP-induced eosinophil infiltration. The different number and distribution pattern of subcutaneously injected WBB6F1-+/+ CMCs between WBB6F1-KitW/KitW-v and WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice appeared to explain the result.
| Materials and Methods |
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Details of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice, previously called WBB6F1-tg/tg mice, were described elsewhere.18 According to standard nomenclature of mutant alleles provided by Mouse Genome Informatics (www.informatics.jax.org), we changed the designation from tg to Mitfmi-vga9. WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice were bred in our laboratory. WBB6F1-KitW/KitW-v and WBB6F1-+/+ mice were purchased from the Japan SLC (Hamamatsu, Japan). All mice were used at 2 to 5 months of age unless stated otherwise and were kept under specific pathogen-free conditions in our animal facility.
Air-Bleb Assay
Infiltration of eosinophils into the mouse skin tissue was estimated by air-bleb assay as described by Lawman and colleagues.24 Briefly, under anesthesia with 50 mg/kg of Nenbutal (Dainippon Pharmaceutical, Osaka, Japan), a volume of 0.9 ml of air was slowly injected into the shaved dorsal skin via a 27-gauge needle with a 1-ml syringe to form an air-bleb, and then 0.1 ml of saline (Otsuka Pharmaceutical, Tokyo, Japan) containing 105 mol/L SP (Sigma-Aldrich, St. Louis, MO), saline containing 300 ng/ml of leukotriene B4 (LTB4) (Sigma-Aldrich), or saline alone, which was present in the same syringe was immediately introduced into the air-bleb. Four hours after the injection, the mice were killed by overinhalation of ether. An interval of 4 hours was chosen according to the result of Matsuda and colleagues.22 The thin connective tissue membrane surrounding the air-bleb was carefully removed and gently stretched onto a glass slide. After air-drying, the specimens were fixed with methanol at room temperature for 10 minutes. They were transferred to a staining jar containing Giemsas solution (Merck, Darmstadt, Germany) freshly 1:10 diluted with phosphate buffer (pH 6.4) (Merck), and were stained for 10 minutes. After washing with water and air-drying, they were cleared with xylene for three times and were mounted with Permount (Fisher Scientific, Pittsburgh, PA). Ten fields were examined per specimen at a magnification of x400. Fields that gave high contrast between eosin-positive cells and other cells were selected at random. The number of eosinophils shown in the result represented the total of eosinophils counted in 10 fields. Air-blebs were sampled at 4, 12, and 24 hours after SP injection. The number of infiltrating eosinophils at particular times after administration of SP was divided by the mean number of eosinophils at the same time after administration of saline alone, and the calculated ratio was used as an index for eosinophil infiltration at indicated time points.
Number and Distribution Pattern of Mast Cells
To count mast cells in the dermis, the dorsal skin was removed and smoothed onto a piece of filter paper to keep them flat, fixed in Carnoys fluid (60% methanol, 30% chloroform, 10% acetic acid), and embedded in paraffin. Sections (4 µm thick) of skin pieces were stained with Alcian blue. Mast cells were counted at a magnification of x200. The number was expressed as mast cells per square millimeter of dermis.
To count mast cells in the subcutaneous connective tissue, a volume of 1-ml of air was injected into the shaved dorsal skin and air-bleb membranes were prepared as describe above. These air-bleb membranes were stained by Giemsas solution. Mast cells were counted as described above in the case of the dermis.
To estimate distribution pattern of injected CMCs in air-bleb membranes, two methods were used. First, we counted 10 fields per Giemsa-stained specimen as described above, and a proportion of fields containing
10 mast cells was determined. Second, we stained the air-bleb membranes with a fluorescence dye, berberine sulfate (Sigma-Aldrich), to highlight only mast cells.17
The specimens were examined by PROVIS AX80 microscope (Olympus, Tokyo, Japan). With this staining, the distribution pattern of mast cells was recognized more easily than with Giemsa staining.
Cellular Area and Fluorescent Intensity
Specimens stained with berberine sulfate were examined with a LSM510 confocal microscope (Carl Zeiss, Oberkochen, Germany). Fluorescent images were collected and processed by a Macintosh computer (Apple Computer, Cupertino, CA). Color information was removed from microscopic images using Adobe Photoshop 7.0 software. Fluorescent cellular region was measured using the public domain NIH Image program (developed at the National Institutes of Health and available on the internet at http://rsb.info.nih.gov/nih-image/). Briefly, the scale was set by using a scale bar in the image. Each fluorescent cell shape was surrounded by using a free line tool. After area and integrated density were selected in the measurement option, the values of the measurement were obtained. The values of integrated density were used for the values of intensity.
Transplantation of CMCs
Pokeweed mitogen-stimulated spleen cell-conditioned medium was prepared according to the method described by Nakahata and colleagues.25
Spleen cells of WBB6F1-+/+ mice were cultured in
-MEM (ICN Biomedicals, Aurora, OH) supplemented with 20% pokeweed mitogen-stimulated spleen cell-conditioned medium and 10% fetal calf serum (Nippon Bio-Supp Center, Tokyo, Japan) for 4 to 5 weeks.12,18
CMCs were harvested, washed, and resuspended in
-MEM at a concentration of 1.0 x 106
cells/0.2 ml. Seven subcutaneous injections were done in the shaved dorsal skin of WBB6F1-KitW/KitW-v and WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. Control mice were injected with culture medium alone. Six weeks after the injection, the air-bleb was produced at the injection site of CMCs.
Number of Eosinophils in Peripheral Blood
Eosinophils were counted on smears of peripheral blood. The smears were air-dried and fixed in methanol for 10 minutes. They were transferred to a staining jar containing Hansels solution freshly diluted with an equal volume of phosphate buffer (pH 7.2, Merck), and stained for 5 minutes. A content of Hansels solution was 1% methylene blue and 0.33% eosin Y in methanol. Two hundred nucleated cells were counted at a magnification of x400.
Bone Marrow Transplantation
A Radioflex 350 X-ray machine (Rigaku, Tokyo, Japan) operated at 180 kV and 15 mA with 1-mm aluminum filter (0.885 Gy/min) was used. Mice were kept in a polypropylene box during irradiation. Bone marrow cells were prepared as described previously.26 Bone marrow cells (1.0 x 107) of WBB6F1-+/+ mice were injected intravenously to eight Gy-irradiated WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice or to two Gy-irradiated WBB6F1-KitW/KitW-v mice. After bone marrow transplantation, the transplantation of WBB6F1-+/+ CMCs was done as described above within the same day. The irradiation dose of WBB6F1-KitW/KitW-v mice was reduced because they were remarkably radiosensitive.27
Semiquantitative Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR)
Total RNAs were extracted from subcutaneous connective tissue by RNeasy (Qiagen, Hilden, Germany). One µg of total RNA was subjected to reverse transcription by Superscript II (Invitrogen, Carlsbad, CA), and the single-strand cDNA was obtained. Reaction mixture (1, 0.1, or 0.01 µl) was added to 25 µl of PCR mixture containing 1.25 U of TaqDNA polymerase (Roche Diagnostics, Mannheim, Germany) and 25 pmol of each of the primers. PCR was performed to amplify the fragment of KITL, MITF, and ß-actin genes using the following primers; 5'-AAGACTCGGGCCTACAATGGACAGCCATGG and 5'-CAATGTTGATACGTCCACAATTAC for KITL, 5'-CGCACCCAACAGCCCTATGGCTATGCTCAC and 5'-GGCTGGACAGGAGTTGCTGATGGTAAGGCC for MITF, and 5'-TAAAGACCTCTATGCCAACAC and 5'-CTCCTGCTTGCTGATCCACAT for ß-actin.
Immunohistochemistry
The skin sections and the air-bleb membranes were used for immunohistochemical analysis. The skin sections were prepared as described previously.28 The air-bleb membranes stretched on the glass were fixed in Carnoys fluid. Samples were incubated sequentially for 10 minutes in methanol containing 0.3% H2O2, for 1 hour at room temperature in phosphate-buffered saline containing 2% bovine serum albumin, and then overnight in 1 µg/ml of polyclonal rabbit anti-stem cell factor (SCF) antibody (IBL, Fujioka, Japan). Samples were washed and then incubated for 1 hour in buffer containing biotin-labeled goat anti-rabbit IgG (IBL). Immunoreactions were detected using AEC+ high-sensitivity substrate-chromogen system (DAKO, Carpinteria, CA) according to the manufacturers instructions.
Statistics
Statistical analysis of data were performed using the Students t-test. Because the number of eosinophils in the air-bleb assay spread widely, a logarithm of each value of infiltrated eosinophils was used for the Students t-test.
| Results |
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By using the air-bleb assay, we examined the effect of mouse genotype on SP-induced eosinophil infiltration. Saline or saline containing SP was injected into the air-bleb, which was formed by the injection of air at the dorsal skin of WBB6F1-+/+, WBB6F1-KitW/KitW-v, and WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. WBB6F1-+/+ mice and WBB6F1-KitW/KitW-v mice were used as positive and negative controls, respectively. Administration of SP significantly increased the number of eosinophils in the air-bleb membranes of WBB6F1-+/+ mice (Figure 1A)
. In contrast, such a significant increase was not observed in WBB6F1-KitW/KitW-v mice. The increase of infiltrating eosinophils was not observed in WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice either (Figure 1A)
. Neutrophil infiltration after administration of SP was not impaired in MITFmi-vga9/MITFmi-vga9 mice (data not shown). We next examined the number of infiltrating eosinophils at 12 and 24 hours after administration of SP. The increase of infiltrating eosinophils was not observed in WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice at 12 and 24 hours (Figure 1B)
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The lack of mast cells appeared to cause the failure of SP-induced eosinophil infiltration in the air-bleb membranes of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. We injected WBB6F1-+/+ CMCs subcutaneously to reconstitute mast cell depletion of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. WBB6F1-KitW/KitW-v mice were used as control recipients, because their mast cell deficiency and failure of SP-induced eosinophil infiltration were normalized by the subcutaneous injection of WBB6F1-+/+ CMCs.22
Although WBB6F1-+/+ CMCs survived in the subcutaneous connective tissue of not only WBB6F1-KitW/KitW-v mice but also WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice, the CMC injection did not increase the number of infiltrating eosinophils induced by SP in the subcutaneous connective tissue of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice (Figure 4)
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Distribution of Transplanted CMCs
The impaired eosinophil infiltration observed in WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice did not appear to be caused by the abnormal function of eosinophils of these mutant mice. The impairment was normalized by the subcutaneous injection of WBB6F1-+/+ CMCs in WBB6F1-KitW/KitW-v mice but not in WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice, indicating that injected WBB6F1-+/+ CMCs did function in the subcutaneous tissue of WBB6F1-KitW/KitW-v mice but not in that of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice.
We compared the number and distribution pattern of mast cells in air-bleb membranes of intact WBB6F1-+/+ mice, WBB6F1-+/+ CMC-injected, or WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMC-injected WBB6F1-KitW/KitW-v mice, and WBB6F1-+/+ CMC-injected or WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMC-injected WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice (Table 2)
. WBB6F1-+/+ CMCs survived in the subcutaneous connective tissue of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice, but WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMCs did not. WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMCs did survive in the subcutaneous connective tissue of WBB6F1-KitW/KitW-v mice, but the mean number of mast cells was nine times greater when WBB6F1-+/+ CMCs were injected than when WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMCs were injected (Table 2)
. The mean number of mast cells was comparable between air-bleb membranes of intact WBB6F1-+/+ mice and those of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice injected with WBB6F1-+/+ CMCs. On the other hand, the mean number of mast cells was two times greater in air-bleb membranes of WBB6F1-KitW/KitW-v mice injected with WBB6F1-+/+ CMCs than in those of intact WBB6F1-+/+ mice (Table 2)
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10 mast cells were detected in most of the high-power fields. Therefore, the proportion of such high-power fields containing
10 mast cells was used as an index of mast cell distribution. The proportion was significantly greater in intact WBB6F1-+/+ mice than in WBB6F1-+/+ CMC-injected WBB6F1-KitW/KitW-v mice. And the proportion was significantly greater in WBB6F1-+/+ CMC-injected WBB6F1-KitW/KitW-v mice than in WBB6F1-+/+ CMC-injected WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice (Table 2)
Air-bleb membranes of intact WBB6F1-+/+ mice and those of WBB6F1-+/+ CMC-injected WBB6F1-KitW/KitW-v and WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice were stained with berberine sulfate. Most mast cells were stained with berberine sulfate in the air-bleb membranes of intact WBB6F1-+/+ and WBB6F1-+/+ CMC-injected WBB6F1-KitW/KitW-v and WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice, suggesting that injected WBB6F1-+/+ CMCs acquired the phenotype of connective tissue-type mast cells in the subcutaneous connective tissue of not only WBB6F1-KitW/KitW-v mice but also WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice (Figure 6)
. Mast cells in the subcutaneous connective tissue of intact WBB6F1-+/+ mice showed a dispersed distribution pattern, whereas those of rescued WBB6F1-KitW/KitW-v and WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice did not show such a dispersed distribution pattern. Injected WBB6F1-+/+ CMCs formed clusters in the subcutaneous tissue of WBB6F1-KitW/KitW-v and WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice (Figure 6)
. The clusters were larger in WBB6F1-KitW/KitW-v mice than in WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. As a result, the areas with normally distributed mast cells, as observed in intact WBB6F1-+/+ mice, were apparently less in WBB6F1-+/+ CMC-injected WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice than in WBB6F1-+/+ CMC-injected WBB6F1-KitW/KitW-v mice (Figure 6)
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| Discussion |
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When CMCs of WBB6F1-+/+ and WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice were transplanted to the subcutaneous connective tissue of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice, WBB6F1-+/+ CMCs but not WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMCs survived. Even if mast cell precursors of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice arrive at their subcutaneous connective tissue, they may not be recognized as differentiated mast cells. When WBB6F1-+/+ CMCs and WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMCs were transplanted to the subcutaneous connective tissue of WBB6F1-KitW/KitW-v mice, mast cells were detected in both cases. However, the number of mast cells was nine times greater when WBB6F1-+/+ CMCs were transplanted than when WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMCs were transplanted. These showed that molecules expressed in WBB6F1-+/+ CMCs but not in WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMCs were important for the survival and differentiation in the subcutaneous tissues. Recently, we found that spermatogenic immunoglobulin superfamily (SgIGSF) that was expressed in WBB6F1-+/+ CMCs but not WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMCs mediated the adhesion between mast cells and fibroblasts. Then, we examined the survival of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMCs overexpressing SgIGSF in the peritoneal cavity of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. The survival of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMCs was partially but not completely rescued by the overexpression of SgIGSF (Ito et al, manuscript submitted). This suggested that other molecules that support the function of SgIGSF might participate in the survival of mast cells.
The transplanted WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMCs differentiate in the subcutaneous connective tissue of WBB6F1-KitW/KitW-v mice but not WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. The subcutaneous connective tissue of WBB6F1-KitW/KitW-v mice was more appropriate for survival and/or differentiation of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMCs than the subcutaneous connective tissue of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. This is consistent with the fact that the number of mast cells was two times greater when WBB6F1-+/+ CMCs were transplanted to the subcutaneous connective tissue of WBB6F1-KitW/KitW-v mice than when they were transplanted in the subcutaneous connective tissue of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. The subcutaneous connective tissue of WBB6F1-KitW/KitW-v mice appeared to be a better environment for survival and/or differentiation of not only WBB6F1-Mitfmi-vga9/Mitfmi-vga9 CMCs but also WBB6F1-+/+ CMCs. There are some explanations for this. The dermis of WBB6F1-KitW/KitW-v mice practically lacked mast cells whereas the dermis of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice contained the decreased but appreciable number of mast cells. Because mast cells express KIT, the concentration of KITL may be greater in WBB6F1-KitW/KitW-v mice than in WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. We attempted to detect KITL protein in the subcutaneous tissues with the immunohistochemistry. Although the expression of KITL in the hair bulbs was detected as described by Peters and colleagues,34 it was not detectable in the subcutaneous connective tissues. Mature mast cells may inhibit development of mast cells from their precursors.35 Mast cells that are present in the dermis of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice might inhibit development of mast cells in their subcutaneous connective tissue.
Administration of SP induced eosinophil infiltration in air-blebs of WBB6F1-+/+ mice but not in those of WBB6F1-KitW/KitW-v mice as reported by Matsuda and colleagues.22 The deficient eosinophil infiltration was normalized by transplantation of WBB6F1-+/+ CMCs. Although the deficiency in eosinophil infiltration was observed in WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice as well, the deficiency of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice was not normalized by the transplantation of WBB6F1-+/+ CMCs. The deficient eosinophil infiltration was not attributable to defects of eosinophils of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mouse origin because of the following two reasons. Eosinophils of WBB6F1-+/+ mouse origin did not infiltrate in air blebs formed in WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice that had received transplantation of both WBB6F1-+/+ bone marrow cells and CMCs. Eosinophils of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice can infiltrate in air-blebs formed in the back of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice after administration of LTB4.
Transplantation of WBB6F1-+/+ CMCs normalized SP-induced eosinophil infiltration in WBB6F1-KitW/KitW-v mice but not in WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. WBB6F1-+/+ CMCs showed comparable cellular area and fluorescent intensity in subcutaneous connective tissue of WBB6F1-KitW/KitW-v mice and in that of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. The greater number of mast cells that appeared in the subcutaneous connective tissue of WBB6F1-KitW/KitW-v mice after transplantation of WBB6F1-+/+ CMCs may explain the difference. Another explanation was the different cluster pattern of injected WBB6F1-+/+ CMCs between WBB6F1-KitW/KitW-v mice and WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. When we counted at random 10 high-power fields of air-bleb membrane injected with WBB6F1-+/+ CMCs, the proportion of fields containing no or few mast cells (less than 10 mast cells) was significantly higher in WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice than in WBB6F1-KitW/KitW-v mice. The microenvironment supporting growth of mast cells may be deficient in WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. In fact, we recently reported that the microenvironment of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice was not suitable for growth of mast cells as compared to that of WBB6F1-KitW/KitW-v mice by using bone marrow and skin transplantations.36 The deficient microenvironment of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice may cause the insufficient distribution of injected WBB6F1-+/+ CMCs, and result in the deficient eosinophil infiltration.
We recently reported a comparable observation in the peritoneal cavity of WBB6F1-KitW/KitW-v and WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice.18
The proportion of death from acute septic peritonitis, which was induced by cecal ligation and puncture, was higher in WBB6F1-KitW/KitW-v mice and WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice than in WBB6F1-+/+ mice. The higher mortality was normalized by the prior intraperitoneal transplantation of WBB6F1-+/+ CMCs in WBB6F1-KitW/KitW-v mice but not in WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. WBB6F1-+/+ CMCs settled not only in the peritoneal cavity but also in the mesentery of WBB6F1-KitW/KitW-v mice, but WBB6F1-+/+ CMCs settled only in the peritoneal cavity of WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice. Because effective neutrophil infiltration occurred only in the rescued WBB6F1-KitW/KitW-v mice, the appropriate anatomical distribution of transplanted WBB6F1-+/+ CMCs appeared to be necessary for the neutrophil infiltration.18
The neutrophil infiltration, which may be induced by tumor necrosis factor-
released by mast cells, is considered to be essential for the defense mechanism against the acute bacterial peritonitis.37,38
Mast cells settled in the mesentery may secrete tumor necrosis factor-
and mediate neutrophil recruitment more efficiently than those settled in the peritoneal cavity, because the probability of localization in the vicinity of blood vessels may be higher in the former than in the latter. The greater number and/or the more dispersed distribution of injected WBB6F1-+/+ CMCs might increase the probability of localization in the vicinity of blood vessels of subcutaneous connective tissues, and might normalize SP-induced eosinophil infiltration in WBB6F1-KitW/KitW-v mice.
Taken together, WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice are useful as the third mast cell-deficient mice. The comparison between WBB6F1-+/+ CMC-transplanted WBB6F1-KitW/KitW-v mice and WBB6F1-+/+ CMC-transplanted WBB6F1-Mitfmi-vga9/Mitfmi-vga9 mice may give insights on relationship between anatomical distribution of mast cells and their physiological functions.
| Acknowledgements |
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| Footnotes |
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Supported by a Grant-in-Aid for Specially Promoted Research from the Ministry of Education, Culture, Sports, Science, and Technology, Japan.
Accepted for publication June 10, 2004.
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