THE BLOOD MAST CELL 



Maximow's words (p. 544), 'whereas in the lower vertebrates the connective 

 tissue mast cells are intimately related to the basophilic blood leucocytes and 

 may originate from them through direct transformation after emigration out 

 of the blood vessels, the mast cells and the mast leukocytes of the mammals 

 seem to be independent cell types'. This independence is well shown in the 

 experiments of Ringoen (1923) who induced a mast leucocytosis in the guinea 

 pig by a subcutaneous injection of egg white and found that although blood 

 mast cells may then migrate into the tissues the cells promptly undergo dis- 

 solution: Zimmermann (1908) likewise experienced no difficulty in recognizing 

 extravasated blood mast cells in the guinea pig. The individuality of blood and 

 tissue mast cells and their separate origin and habitat in higher vertebrates are 

 thus clear. 



However, as Maximo w (1910) observed, there does appear to be a certain 

 degree of reciprocity between the numbers of blood and tissue mast cells in 

 various species, suggesting perhaps that both types of cell subserve the same 

 biological function. Thus, among the mammals, blood mast cells preponderate 

 in the rabbit, whereas in rat, mouse and most other species the tissue mast cells 

 far outnumber the mast cells produced by the marrow. Michels (1923) found 

 the tissues of certain species of fish to contain 'an incomparable abundance' 

 of mast cells. His statement that mast cells are entirely lacking in the blood of 

 fishes has been criticized by Loewenthal (1930), though the numbers of blood 

 mast cells in fish are never large. The proportion of mast cells in human blood 

 remains remarkably constant at 0-5-1-0 per cent of all leucocytes and is not 

 affected by local increase in tissue mast cells (Heller, 1904; Pappenheim, 1909; 

 Staemmler, 1921; Ellis, 1949). These small values are perhaps best expressed 

 as the absolute basophil count, the number of cells per c.mm. blood (Moore 

 and James, 1953). A raised basophil count is a regular feature of chronic 

 myeloid leukaemia (Ehrlich, 1891; Heller, 1904; Holmgren and Wohlfart, 

 1941) and tends to remain high even after the polymorph count has been 

 reduced by irradiation (Sabrazes, 1926). True basophilic leukaemia in man 

 is extremely rare (Joachim, 1906; Doan and Reinhart, 1941; Hule, 1950; 

 Lennert et al, 1956). Very recently two cases of so-called tissue mast-cell 

 leukaemia have been reported (Efrati, et al, 1957; Friedman et al, 1958). 



Tissue mast cells in bone marrow 



In addition to the mast myelocytes which produce the blood mast cells, 

 an occasional tissue mast cell is seen in smears or sections of human bone 

 marrow, being easily recognized by its large size and dense content of darkly 

 staining metachromatic granules. According to Jordan and Speidel (1924a) 

 tissue mast cells are comparatively common in the subcortical region of the 

 femoral marrow of the normal rabbit, and one has seen them in small numbers 



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