There has been major interest in the potential interaction between blood coagulation and inflammation. Most of the effort has focused on cellular interactions involving platelets and polymorphonuclear leukocytes (PMNS). The recent discovery of tissue kallikrein(TK) activity in PMNs prompted the study of the possible role of thrombin(IIa) in this process. Human PMNs were isolated by density gradient centrifugation. Human IIa was compared with fMLP with respect to chemotaxis and enzyme release. Results from the challenges by IIa and fMLP were compared to a NaCl control using Student's paired t-test. IIa was a potent chemotactic agent for PMNs (p less than or equal to 0.0121) and stimulated the release of TK (p less than or equal to 0.0001) as determined by hydrolysis of S-2266. FMLP significantly stimulated PMN chemotaxis (p less than or equal to 0.0028) but had no effect on TK release. Release of TK was confirmed by Western Blot analysis and 35S-methionine incorporation into a 35 KD protein after IIa challenge. These results demonstrate that IIa is chemotactic for PMNs and can cause release of tissue kallikrein demonstrating a direct role for blood coagulation in the regulation of the inflammatory response.