Characterization of neutrophil iodination for the assessment of phagocytic and opsonic function in septic patients

To increase our understanding of the nature of surgical infection, further studies on the host defense abilities of infected patients are required. Therefore, a more thorough investigation of the iodination method for the measurement of polymorphonuclear leukocyte function and serum opsonic activity was undertaken to characterize its application in surgical infection. A significant relationship was found between the phagocytic indices derived from different standard neutrophils or sera measured on the same day. When expressed as a value of normal phagocytic indices minus abnormal phagocytic indices, this relationship was constant from day to day despite wide variations in the absolute phagocytic index values. This finding enables direct comparisons to be made between the values obtained both from the same patient and from different patients during the course of their illness by reference to daily control values. We also found that the system was sufficiently sensitive to detect, in a dose-responsive manner, the changes induced in normal neutrophil phagocytosis and serum opsonic activity by a specific bacterial challenge with either K. pneumoniae or E. coli. In addition, zymosan, which is utilized in the iodination reaction but also has immunoadjuvant properties, was found to enhance neutrophil function but depress serum opsonic activity in the face of such bacterial challenges. We conclude that the iodination technique is a credible method for the indirect measurement of polymorphonuclear phagocytosis and serum opsonic function in the face of a bacterial challenge and can be reliably employed in studies of septic patients provided these findings are taken into account.