MAST-CELL AND EOSINOPHIL DISTRIBUTION AND ACTIVATION IN HUMAN ENDOMETRIUM THROUGHOUT THE MENSTRUAL-CYCLE

Tryptase and chymase immunolocalization techniques have been used to e xamine the distribution, activation, and tryptase/chymase phenotype of mast cells (MCs) in 107 endometrial specimens that represented every day of the hu man menstrual cycle. MCs were identified in the endometr ium in all stages of the menstrual cycle; similar MC numbers were obse rved for the functionalis, basalis, and muscularis. Extensive MC activ ation/degranulation, as judged by extracellular tryptase, was a common feature of the functionalis in specimens sampled just prior to and du ring menstruation. MC activation was also prominent in the functionali s at times coincident with recognized stromal edema. MCs of the functi onalis did not contain chymase; all stained for tryptase acid represen t the MC(T) phenotype. By contrast, the basalis and muscularis showed a proportion of MCs containing both tryptase and chymase, MC(TC). One important function for extracellular MC tryptase and chymase is their ability to activate precursor forms of the matrix metalloproteinases, enzymes recognized as instrumental in stromal degradation. Quantitativ e analysis of MC numbers, expressed relative to stromal cell numbers/m m(2), indicated no major changes during the menstrual cycle, although changes in MC morphology, granule content, and activation/degranulatio n were recognized for specific stages. Eosinophils, detected with mono clonal antibodies EG1 and EG2, were absent from extravascular sites be tween Days 5 and 26 but showed local accumulations just prior to and d uring menstruation, Since MCs and eosinophils between them contain a v ariety of potent mediators, it seems likely that both cell types assum e important functional roles in relation to tissue and vascular remode ling associated with endometrial physiology.