Preferential inhibition of primary granule release from bovine neutrophils by a Brucella abortus extract

A low-molecular-weight Brucella abortus extract (a nucleotidelike material) inhibited zymosan-elicited neutrophil degranulation and trichloroacetic acid-precipitable protein iodination (a measure of myeloperoxidase and H2O2 release from neutrophilic leukocytes). Inhibition of neutrophil function was directly related to the concentration of the Brucella extract. The extract preferentially inhibited degranulation of primary (azurophilic or peroxidase positive) granules and had limited inhibition of secondary (specific or peroxidase negative) granule release but did not inhibit opsonized zymosan ingestion. Inhibition of protein iodination closely paralleled that of primary granule release but was unrelated to inhibition of secondary granule release. These results suggest that B. abortus has a component which is capable of inhibiting release of myeloperoxidase by dose-dependent preferential inhibition of primary granule release from bovine neutrophilic leukocytes.