Abstracts (complete list) - Wissenschaft Online

Christian Menge, Evelyn A. Nystrom
Dexamethasone depletes γδT cells and alters the activation
state and responsiveness of bovine peripheral blood
lymphocyte subpopulations
Administration of dexamethasone (DEX) to cattle is commonly used in models of stressinduced
effects on the host defense. Even though the effects of DEX on the bovine
adaptive immune are not fully elucidated yet. Previous studies showed that lymphocyte
subsets are differentially affected by DEX. The objective of the present study was to
characterize subsets of circulating lymphocytes in calves prior to and 48 h after the
onset of parenteral DEX treatment. Treatment significantly reduced the overall
percentage of circulating lymphocytes, and disproportionately depleted the population of
γδTCR+/CD8α- cells. Analysis within the CD8α+ population of T cells further revealed
that DEX treatment also reduced the CD8αlow subset of γδT cells coexpressing the
activation marker ACT-2+. By contrast, DEX treatment did not affect the percentage of
CD8αlow/CD25+ cells, indicating that cells with a special activation state were affected.
Despite a sharp increase in the number of CD25+ PBMC from DEX-treated calves, only
marginal differences were noted in the percentages and the proliferative capacity of the
major lymphocyte subsets. Transcription of several Th-prototype cytokines (IL-2, IFN-γ,
IL-4, TGF-β) was reduced in short term-PBMC cultures from DEX-treated calves, sparing
il-10. The results of this study extend the evidence that DEX treatment does not
generally suppress the bovine immune system but has a number of different effects on
different lymphocyte subpopulations. This information must be considered when utilizing
DEX treatment to improve bovine infection models.