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Regulation of bovine gamma/delta T cell responses

Thillainayagam Sathiyaseelan, University of Massachusetts Amherst

Abstract

Bovine γδ T cells are activated by a cell surface antigen found on autologous monocytes in in vitro cultures. This response is known as the autologous mixed leukocyte reaction (AMLR). I found AMLR stimulation is mediated through the T cell receptor since it was blocked by Fab fragments of an anti-δ TCR mAb. Purified γδ T cells directly responded to monocyte stimulation in AMLR. We found that the stimulatory molecule on monocytes was not a peripheral membrane-associated or GPI-anchored component but an integral membrane protein. An anti-monocyte monoclonal antibody (M5) was generated in mice and shown to block the proliferation induced by monocytes in the AMLR. The ligand for mAb M5 was found on bovine and sheep monocytes, which have the capacity to stimulate AMLR, but not on human or murine macrophages that were previously shown to be non-stimulatory in the AMLR. When proliferation and cytokine production were evaluated, γδ T cells responded poorly to stimulation through the TCR alone using anti-CD3 mAb, in contrast to CD4+ and CD8+ T cells that responded well. However when stimulated with monocytes in the AMLR, 70–90% of the responding cells were γδ T cells, as assessed by IFN-γ production using flow cytometry. Stimulation through the WC1 receptor by three mAb augmented the proliferation of T cells induced by suboptimal levels of anti-CD3 or anti-δ TCR mAb and direct stimulation of WC1 by mAb produced profound IFN-γ production by γδ T cells as shown by 2-color immunofluorescence. These data strongly suggest that WC1 is functioning as a co-stimulatory molecule for γδ T cell activation. We propose a model that monocytes provide the main stimulatory signals via the M5 ligand through the γδ TCR and co-stimulatory signals by the WC1 ligand through WC1, which together result in proliferation and high IFN-γ production in the AMLR. Thus, the major immune function of bovine γδ T cells may be their rapid and strong IFN-γ production which activates macrophages.

Subject Area

Immunology|Cellular biology|Molecular biology

Recommended Citation

Sathiyaseelan, Thillainayagam, "Regulation of bovine gamma/delta T cell responses" (2001). Doctoral Dissertations Available from Proquest. AAI3000341.
https://scholarworks.umass.edu/dissertations/AAI3000341

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