AIMS: In a group of patients undergoing cardiac surgery performed both with ("on-pump") and without the use ("offpump") of cardiopulmonary bypass (CPB), we studied the changes of neutrophil membrane apoptosis-inducing complex Apo/Fas. METHODS: Expression of Apo/Fas (CD95) on leukocytes was evaluated by flow cytometry. RESULTS: In "on-pump" patients, we found an increase in the expression of CD95 median intensity fluorescence (MFI) on granulocytes from a baseline level median=56, (Q( 1)=45.5, Q(3)=64) to a median=88, (Q(1)=62, Q( 3)=109.5; p<0.01) at the 3(rd) postoperative day and median=74, (Q(1)=63, Q(3)=84.5; p<0.01) at the 7(th) postoperative day. In "off-pump" patients, granulocyte CD95 MFI was median=55, (Q(1)=51, Q(3)=84) before surgery. The significant increase was found on the 3(rd) postoperative day only; median=90, (Q( 1)=66; Q(3)=98; p<0.05). A similar pattern in the CD95 expression was also found if percentage changes of granulocyte CD95 MFI were followed. Moreover, the significantly increased Apo/Fas expression expressed as a percentage change of CD95 MFI was found in "on-pump" patients compared to "off-pump" patients, both at the 3(rd) postoperative day (p<0.05) and at the 7(th) postoperative day (p<0.01). CONCLUSIONS: This is the first direct evidence of increasing densities of the Apo/Fas complex on neutrophils in cardiac surgical patients.

Department of Cardiac Surgery Charles University Prague University Hospital and Medical Faculty in Hradec Kralove Hradec Kralove Czech Republic

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