Luminescence studies of the phagocyte response to endotoxin infusion into normal human subjects: multiple discriminant analysis of luminescence response and correlation with phagocyte morphologic changes and release of elastase

A blood luminescence system (BLS) was employed to analyze blood phagocyte function in response to infusion of endotoxin (4 ng Escherichia coli lipopolysaccharide (LPS)/kg body weight) into 7 healthy human subjects. The subjects were closely monitored clinically, and extensive chemical, hematological and coagulation measurements were taken during the pretreatment, early (symptomatic, 1-8 h post-LPS), and late (asymptomatic, 12-48 h post-LPS) phases of acute inflammation. BLS assessment included measurement of basal and PMA-stimulated phagocyte oxidase and myeloperoxidase (MPO) activities, and also included measurement of circulating (COR) and PAF-primed maximum (MOR) opsonin receptor-dependent phagocytic activities. Basal oxidase activity peaked at T+1 h and showed an additional peak at T+24 h post-LPS. The COR activity also peaked at 1-2 h, but remained elevated through T+23 h post-LPS,while the basal MPO activity peaked only once at T+1 h. We concluded that while MPO evidence of phagocyte respiratory activation returned to baseline by T+4 h, COR evidence of receptor expression (receptor alert) remained elevated through T+24 h. During this early (0-8 h) period, elastase/alpha 1AT complex concentration peaked at T+3-4 h and again at T+8 h. Peak numbers of circulating polarized and vacuolated phagocytes also appeared at T+3-4 h and 7 h. We concluded that there was biochemical and morphological evidence of continuing phagocyte activity beyond T+4 h to T+8 h, and that this corresponded with the period during which the subjects were symptomatic. In addition, the appearance of a second peak of basal oxidase activity at T+24 h, multiple discriminant analyses of all the luminescence data, and the sustained elevation of lactate suggested that there was a later second stage (T+12 h to 48 h) of the human response to endotoxin, during which time the subjects were asymptomatic.