FIXATION WITH CARNOYS FLUID REDUCES THE NUMBER OF CHYMASE-POSITIVE MAST-CELLS - NOT ALL CHYMASE-POSITIVE MAST-CELLS ARE ALSO POSITIVE FOR TRYPTASE

Mast cells in the nasal mucosa can be studied by means of monoclonal a ntibodies (mAb) against tryptase (T(+)MC) and chymase (C(+)MC). Fixati on with acetone gives more positive cells than does fixation with Carn oy'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 w ith Carnoy's fluid, however, the number of T(+)MC is larger than the n umber 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 1 0 min. Within 1 min, the number of C(+)MC decreases to a level where c ontinued fixation no longer gives further decreases in the number of c ells. Two populations of mast cells can be distinguished here: one sen sitive and the other insensitive to Carnoy's fluid. When double-staini ng is used, fixation with acetone gives three populations of mast cell s: one positive for tryptase (T(+)C(-)MC), another positive for trypta se and chymase (T(+)C(+)MC), and a third one positive for chymase (T(- )C(+)MC). These three populations were found in lymph node, spleen, th ymus, dermis, lung parenchyma, small intestinal submucosa, and nasal m ucosa.