1Department of Immunology and Bronchial Asthma Research Unit, Medical Research Institute, University of Alexandria, Egypt and ²Department of Immunology, Rheumatism and Allergy Research Unit, Medical School University of Birmingham. UK.

Collagenase from Cl histolyticum was found capable of inducing, non-cytolytically, histamine release from Percoll-purified rat peritoneal mast cells. The release process is rapid, reaching maximum by one minute. It is also temperature as well as pH-dependent. High non-therapeutic concentrations of DSCG were needed to inhibit collagenase-induced histamine release, but this inhibitory effect was not concentration-dependent. These features of collagenase-induced histamine release favours the basicity of its structure as a possible underlying mechanism of how mast cells are stimulated by this enzyme, however, pmsf [phenyl methyl sulphonyl flouride] which is known to be a non-specific serine protease inhibitor was found capable, at high concentrations, of inhibiting the histamine releasing activity of collagenase. Further characterization of this newly assigned activity to collagenase is required especially so with the availability of purified forms of the human neutrophil analogs and specific enzyme inhibitors.