Human lung mast cells: distribution and abundance of histochemically distinct subpopulations.

Methods originally employed to demonstrate the heterogeneity of mast cells in the rat and more recently in the human intestine were used to study mast cell heterogeneity in the human bronchial mucosa and lung parenchyma. Thus, a quantitative survey of pulmonary mast cells using different fixation and staining procedures indicated that two distinct mast cell subpopulations (formalin-sensitive and formalin-resistant) are present and have distinct patterns of distribution and abundance. The findings are of potential clinical importance because histochemical heterogeneity may be a marker of functional mast cell differences in humans including differences in responsiveness to antiallergic drugs, as occurs in rats. The findings also indicate that conventional methods of fixation are likely to lead to a gross underestimation of total mast cell numbers.