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  • Author or Editor: Gayle B. Brown x
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SUMMARY

Cattle persistently infected with bovine viral diarrhea (bvd) virus have decreased neutrophil and lymphocyte functions. We reevaluated these functions and further characterized the inhibition of persistent bvd virus infection in neutrophils, using sensitive kinetic assays. In addition, the influence of in vitro incubation of neutrophils with recombinant bovine interferon gamma (rBoifn gamma) and in vitro incubation of lymphocytes with recombinant bovine interleukin-2 was evaluated.

Significant (P < 0.05) decrease in random migration under agarose, Staphylococcus aureus ingestion, cytochrome-C reduction, iodination, antibody-independent cell-mediated cytotoxicity, oxidant production, and cytoplasmic calcium flux were observed in neutrophils from cattle persistently infected with bvd virus, compared with noninfected control cattle. Incubation of neutrophils from noninfected controls with rBoifn gamma significantly (P < 0.05) decreased random migration under agarose, cytochrome-C reduction, and cytoplasmic calcium flux. Neutrophils from cattle persistently infected with bvd virus also had decreased random migration under agarose after incubation with rBoifn gamma; in addition, antibody-independent cell-mediated cytotoxicity, elastase release, and cytoplasmic calcium flux were significantly enhanced. The rBoifn gamma induced significantly (P < 0.05) different effects on chemotaxis, cytochrome-C reduction, iodination, and cytoplasmic calcium flux of neutrophils from infected and control cattle. The rBoifn gamma was more effective at improving the function of neutrophils from cattle persistently infected with bvd virus, compared with neutrophils from controls.

Lymphocytes from infected cattle had decreased histogenesis in response to phytohemagglutinin, concanavalin A, and pokeweed mitogen. Incubation of those lymphocytes with recombinant bovine interleukin-2, with no mitogen present, significantly (P < 0.05) increased incorporation of [3H]thymidine. However, the response of lymphocytes to mitogen stimulation was not significantly increased by the presence of recombinant bovine interleukin-2, indicating that depression of in vitro lymphocyte histogenesis in the cattle persistently infected with bvd virus is not attributable to decreased production of interleukin-2.

Free access
in American Journal of Veterinary Research

SUMMARY

Leukocytosis (34,600 wbc/μl of blood) was detected in an apparently healthy 7-day-old Holstein heifer. Analysis of blood samples obtained over the next 41 days revealed chronic progressive neutrophilia, which peaked at > 85% neutrophils and exceeded 100,000 wbc/μl. In vitro assessment of isolated blood neutrophils obtained from the heifer at 38 and 45 days of age revealed selected functional abnormalities. Endocytosis of immunoglobulin-opsonized Staphylococcus aureus and killing of this test organism by the calf’s neutrophils were significantly diminished, as were phagocytosis-associated superoxide generation, chemiluminescence activity, and myeloperoxidase-catalyzed iodination. Diminished H2O2 elaboration by the calf’s neutrophils was evident during ingestion of opsonized zymosan or on exposure to phorbol myristate acetate. Extracellular release (secretion) of elastase during ingestion of zymosan was also diminished, although total cell content of elastase was normal, compared with that of neutrophils from age-matched calves, and granular or other morphologic abnormalities of the calf’s neutrophils were not evident by ultrastructural examination. Abnormalities of random migration were inconsistently detected, and normal or high degree of antibody-dependent cytotoxicity or natural killing by the calf’s neutrophils was observed. Similar in vitro assessment of neutrophils obtained from the calf’s dam revealed no functional abnormalities. The calf died at 48 days of age, with persistent fever and chronic diarrhea, despite administration of antibiotics. Histologic examination at necropsy revealed large numbers of intravascular neutrophils in most tissues, including massive neutrophil sequestration in spleen. However, a striking lack of extravascular neutrophils was evident in inflamed submucosa adjacent to intestinal ulcers heavily contaminated with enteric microorganisms. Bone marrow examination revealed diffuse myeloid hyperplasia, but no other abnormalities.

The clinical and pathologic features in this calf were similar to those in previously reported human patients or Irish Setters with genetic deficiency of the CD11/CD18 leukocyte glycoprotein complex, thus prompting further postmortem evaluations. Results of immunoblot analyses of the neutrophil lysates of the heifer calf (isolated and stored prior to death) documented severe deficiency of Mac-1 (CD11b/CD18). Results of immunofluorescent analyses indicated substantially diminished (intermediate) amounts ofthe Mac-1 β subunit (CD18) on blood neutrophils of the calf's dam and sire and on neutrophils of 8 of 15 paternal half-siblings; findings were consistent with an autosomal recessive trait in the proband's kindred. Findings also indicate that genetic abnormalities of CD11/CD18 proteins may underlie the molecular pathogenesis of disease in this calf as well as other previously described examples of the granulocytopathy syndrome in Holstein cattle.

Free access
in American Journal of Veterinary Research