Mast cells and macrophages in normal C57/BL/6 mice.
Mast cells and macrophages have an important role in immunity and inflammation. Because mice are used extensively for experimental studies investigating immunological and inflammatory responses, we examined mast cell and macrophage distribution in normal murine tissues. Mast cells were abundant in the murine dermis, tongue, and skeletal muscle but were rarely found in the heart, lung, spleen, kidney, liver, and the bowel mucosa. In contrast, dogs exhibited large numbers of mast cells in the lung parenchyma, liver, and bowel. Some murine dermal mast cells had long cytoplasmic projections filled with granular content. Mouse mast cells demonstrated intense histamine immunoreactivity and were identified with histochemical enzymatic techniques for tryptase and chymase. Macrophages, identified using the monoclonal antibody F4/80, were abundant in the spleen, lung, liver, kidney, and bowel but relatively rare in the heart, tongue, and dermis. Using a nuclease protection assay we investigated mRNA expression of stem cell factor (SCF), a crucial survival factor for mast cells, and the macrophage growth factors macrophage colony stimulating factor (M-CSF) and granulocyte macrophage colony stimulating factor (GM-CSF). Stem cell factor mRNA was highly expressed in the murine lung. Relatively low levels of SCF mRNA expression were found in the tongue and earlobe, which are tissues containing a high number of mast cells. Macrophage CSF and GM-CSF mRNA was highly expressed in the lung and spleen. The murine heart, an organ with a low macrophage content, expressed high levels of M-CSF but negligible levels of GM-CSF mRNA. Constitutive growth factor mRNA expression in murine tissues without significant populations of mast cells and macrophages may suggest an alternative role for these factors in tissue homeostasis.
Gersch
Christine
C
Section of Cardiovascular Sciences, Baylor College of Medicine, One Baylor Plaza M/S F-602, Houston TX 77030, USA.
Dewald
Oliver
O
Zoerlein
Martin
M
Michael
Lloyd H
LH
Entman
Mark L
ML
Frangogiannis
Nikolaos G
NG
D000818:Animals; D053818:Chymases; D004285:Dogs; D006133:Growth Substances / Q000235:genetics; D008264:Macrophages / Q000166:cytology* / Q000201:enzymology; D008407:Mast Cells / Q000166:cytology* / Q000201:enzymology; D051379:Mice; D008810:Mice, Inbred C57BL; D009928:Organ Specificity; D012333:RNA, Messenger / Q000378:metabolism; D012697:Serine Endopeptidases / Q000032:analysis; D053802:Tryptases
D006133:Growth Substances; D012333:RNA, Messenger; C509190:Tpsb2 protein, mouse; D012697:Serine Endopeptidases; D053818:Chymases; C509222:Tpsab1 protein, mouse; D053802:Tryptases