Kinetic analysis of microbe opsonification based on stimulated polymorphonuclear leukocyte oxygenation activity

Abstract

With Pseudomonas aeruginosa as the target microbes and polymorphonuclear leukocytes (PMNL) as effector phagocytes, the microbe-specific, immunoglobulin G (IgG)-dependent opsonic capacities of preimmune and immune sera were measured as the rate of stimulated PMNL dioxygenation of luminol yielding chemiluminescence (CL). When the reactants other than opsonin are present in concentrations that are not rate limiting, the information-effector relationship linking specific opsonin concentration to effector PMNL stimulation is described by the rate equation: L' = k'[IgG]i, where L' is the peak CL velocity (photons per minute), k' is the proportionality constant, [IgG] is the concentration of specific opsonin, and the exponent i is the order of the reaction with respect to opsonin. Since the specific opsonins were polyclonal IgG of unknown absolute serum concentration, the reciprocal rate expression, L' = k'D-i, was employed for data presentation; D is the serum dilution (final volume/initial serum volume), and the sign of i is changed to negative. The relationships of integral, first-derivative, and second-derivative expressions of the CL response to opsonin concentration are illustrated with experimentally obtained data. Based on peak CL velocity or peak CL acceleration measurements taken over different time intervals of testing, the estimated order with respect to opsonin is highest, and probably most accurate, using the shortest test interval allowing reasonably good precision of measurement. As an alternative temporal approach, microbe opsonification kinetics are analyzed based on nodal time (Tn) measurements. The Tn is the time point separating the acceleration and deceleration phases of the PMNL oxygenation response to stimulation and as such satisfies the criterion of a selected condition of PMNL activation.