Heparin in Clinical Doses 'Primes' Granulocytes to Subsequent Activation as Measured by Myeloperoxidase Release

The author pre-incubated isolated human granulocytes with increasing doses of heparin (0–100 IU/mL) before subsequent stimulation with formyl-met-leu-phe. There was a dose-dependant increase in granulocyte activation as measured by myeloperoxidase release, quantitated in enzyme-immunoassay. This 'priming' effect of heparin was not due to activation of contaminating platelets or to endotoxin, and there was no reduction in granulocyte viability. Heparin-induced 'priming' of granulocytes may be clinically relevant in the setting of cardiopulmonary bypass. The author describes a sensitive and specific double antibody enzyme-immunoassay for myeloperoxidase from human granulocytes, with an inter-assay coefficient of variation of 12.6%, an intra-assay coefficient of variation of 4.3%, and a lower detection limit of 1.8 μg/l.