Activation of the bactericidal capacity of polymorphonuclear granulocytes after surgery, measured with a new in vitro assay.

A classic in vitro polymorphonuclear (PMN) granulocyte bactericidal system was used alongside a newly developed modification to see whether the new assay would increase the possibility to detect a stimulation of PMN bactericidal functions. In the new assay each granulocyte was provided with 30--40 bacteria, which is quite close to the maximal killing capacity (usually 60 bacteria per PMN). Granulocytes were obtained from 8 patients the day before, the day after and 2 d after they underwent thoracotomy with cardiopulmonary by-pass (CPS). The granulocytes from all patients showed an increased capacity to kill Staph. aureus in vitro 2 d after the operation, compared to before, when the submaximal bacterial concentration per granulocyte was used, whereas no change was observed with the standard bacterial concentration (3--4 bacteria per granulocyte). Thus, the new assay might make it possible to observe an enhanced PMN bactericidal ability.