Fixation with Carnov's fluid reduces the number of chymase-positive mast cells: not all chvmase-Dositive mast cells are also posithe for iryptase

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Abstract
Mast cells in the nasal mucosa can be studied by means of monoclonal antibodies (mAb) against tryptase (T+MC) and chymase (C+MC). Fixation with acetone gives more positive cells than does fixation with Carnoy's fluid. In frozen biopsy specimens of allergic nasal mucosa fixed with acetone, the number of T+MC equals that of C+MC. When fixed with Carnoy's fluid, however, the number of T+MC is larger than the number of C+MC. The decrease in both T+MC and C+MC resulting from fixation with Carnoy's fluid is time‐related and depends on the type of mAb used. Carnoy fixation time gives a decrease in the number of C+MC within 1 min, whereas the number of T+MC decreases only after 10 min. Within 1 min, the number of C+MC decreases to a level where continued fixation no longer gives further decreases in the number of cells. Two populations of mast cells can be distinguished here: one sensitive and the other insensitive to Carnoy's fluid. When double‐staining is used, fixation with acetone gives three populations of mast cells: one positive for tryptase (T+C‐MC), another positive for tryptase and chymase (T+C+MC), and a third one positive for chymase (T‐C+MC). These three populations were found in lymph node, spleen, thymus, dermis, lung parenchyma, small intestinal submucosa, and nasal mucosa.