[Mast cells in ulcerative colitis]

Authors have studied the changes in number and electronmicroscopic appearances of mast cells in the mucosa of large intestine of patients suffering from colitis ulcerosa either in its active or remission period. Counting of cells was performed in osmium-fixed, semithin, Giemsa-stained sections to avoid variations in staining due to formaldehyde. In the active stage of the disease the increase in number of mast cells was significant. Their pronounced degranulation was evident in both semi- and ultrathin preparations. Two forms of degranulation were distinguished: 1. by the release of granules; 2. by the extrusion of whole cytoplasmic areas. The latter indicated fast degranulation, in accordance with observations in animal experiments. Mast cells became closely related to the capillaries, Schwann-cells and nerve fibres of the lamina propria, with myofibroblasts and collagenous fibres. At some places they were found between the epithelial cells of Lieberkühn's crypts. It is assumed that this close topographical correlation represents also functional connections. The present morphological findings corroborate current hypotheses and suggest that the increase in number of mast cells in the active stage of coliitis ulcerosa mediates an hyperergic reaction.