Date of Award

1990

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Frederick M. Enright

Second Advisor

Kent A. Gossett

Abstract

Functional activities of monocyte-derived macrophages and serum killing ability in a population of Brucella abortus-naive cows were evaluated. The ability of these macrophages to phagocytize and control intracellular survival of B.abortus and to produce oxidant was measured. Fresh normal bovine sera killed significantly more B.abortus than reactor serum or fetal bovine serum. When heated to destroy complement, none of the sera were capable of significant killing. The ability of sera from B.abortus-naive cows to kill the bacteria was normally distributed, with all animals within $\pm$ 2 sd of the mean. Phagocytosis of bacteria opsonized with autologous or reactor sera was significantly greater than phagocytosis of bacteria opsonized with fetal bovine serum. After phagocytosis, bacteria opsonized with autologous, reactor, or fetal bovine serum displayed no differences in their ability to survive within macrophages. The abilities of the macrophages to phagocytize and to kill B.abortus were not significantly correlated. Phagocytosis and killing activities of macrophages from individual cows were normally distributed. Oxidant production by monocyte-derived macrophages was compared to that by neutrophils after stimulation with phorbol myristate acetate, opsonized zymosan, or B.abortus opsonized with autologous, reactor, or fetal bovine serum. Neutrophils responded faster to all stimuli, and produced up to 100 fold more oxidant than macrophages. PMA stimulated significantly more oxidant from macrophages than opsonized zymosan or opsonized B.abortus. Macrophages and neutrophils stimulated with opsonized zymosan, and reactor serum-opsonized B.abortus had higher mean oxidant production than cells exposed to the other stimuli, suggesting receptor specific initiation of the respiratory burst. Four cows were identified as potential outliers based on oxidant production greater than 2 sd from the mean. There was no correlation between oxidant production and intracellular survival of the bacteria.

Pages

108

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