Effects of dexamethasone on cell-mediated immune responses in cattle sensitized to Mycobacterium bovis

Michael L. Doherty From the Faculty of Veterinary Medicine, University College Dublin, Ballsbridge, Dublin 4, Ireland (Doherty, Bassett, Quinn, Monaghan), and the Department of Veterinary Microbiology and Pathology and Animal Health Research Center, Faculty of Veterinary Medicine, Washington State University, Pullman, WA 99164 (Davis).

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Hugh F. Bassett From the Faculty of Veterinary Medicine, University College Dublin, Ballsbridge, Dublin 4, Ireland (Doherty, Bassett, Quinn, Monaghan), and the Department of Veterinary Microbiology and Pathology and Animal Health Research Center, Faculty of Veterinary Medicine, Washington State University, Pullman, WA 99164 (Davis).

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Patrick J. Quinn From the Faculty of Veterinary Medicine, University College Dublin, Ballsbridge, Dublin 4, Ireland (Doherty, Bassett, Quinn, Monaghan), and the Department of Veterinary Microbiology and Pathology and Animal Health Research Center, Faculty of Veterinary Medicine, Washington State University, Pullman, WA 99164 (Davis).

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William C. Davis From the Faculty of Veterinary Medicine, University College Dublin, Ballsbridge, Dublin 4, Ireland (Doherty, Bassett, Quinn, Monaghan), and the Department of Veterinary Microbiology and Pathology and Animal Health Research Center, Faculty of Veterinary Medicine, Washington State University, Pullman, WA 99164 (Davis).

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Michael L. Monaghan From the Faculty of Veterinary Medicine, University College Dublin, Ballsbridge, Dublin 4, Ireland (Doherty, Bassett, Quinn, Monaghan), and the Department of Veterinary Microbiology and Pathology and Animal Health Research Center, Faculty of Veterinary Medicine, Washington State University, Pullman, WA 99164 (Davis).

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SUMMARY

Systemic administration of dexamethasone led to a significant reduction in the size of the tuberculin reaction in response to intradermal injection of bovine purified protein derivative in 18 cattle experimentally sensitized to Mycobacterium bovis (P < 0.01) and 8 cattle naturally infected with M bovis (P < 0.001). The reaction in 6 of the 7 M bovis-infected cattle that received dexamethasone was classified as negative for the standard interpretation of the single intradermal comparative tuberculin test. Significantly fewer BoCD2+ (P < 0.05) and BoCD4+ T cells (P < 0.001) were present at the reaction site and in blood of dexamethasone-treated cattle, compared with untreated control cattle. Significantly fewer cells expressing the interleukin-2 receptor and WC1+ γδ T cells (P < 0.001), and a significantly greater number of cells expressing the ACT2 antigen (P < 0.05) were found at the reaction site in dexamethasone-treated cattle than in controls. The number of BoCD8+ T cells at the reaction site and in blood was not significantly affected by administration of dexamethasone. In vitro production of interferon-γ by lymphocytes incubated with bovine purified protein derivative also was significantly lower (P < 0.01) in the dexamethasone-treated cattle.

SUMMARY

Systemic administration of dexamethasone led to a significant reduction in the size of the tuberculin reaction in response to intradermal injection of bovine purified protein derivative in 18 cattle experimentally sensitized to Mycobacterium bovis (P < 0.01) and 8 cattle naturally infected with M bovis (P < 0.001). The reaction in 6 of the 7 M bovis-infected cattle that received dexamethasone was classified as negative for the standard interpretation of the single intradermal comparative tuberculin test. Significantly fewer BoCD2+ (P < 0.05) and BoCD4+ T cells (P < 0.001) were present at the reaction site and in blood of dexamethasone-treated cattle, compared with untreated control cattle. Significantly fewer cells expressing the interleukin-2 receptor and WC1+ γδ T cells (P < 0.001), and a significantly greater number of cells expressing the ACT2 antigen (P < 0.05) were found at the reaction site in dexamethasone-treated cattle than in controls. The number of BoCD8+ T cells at the reaction site and in blood was not significantly affected by administration of dexamethasone. In vitro production of interferon-γ by lymphocytes incubated with bovine purified protein derivative also was significantly lower (P < 0.01) in the dexamethasone-treated cattle.

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