Comparative gene expression by WC1+ γδ and CD4+ αβ T lymphocytes, which respond to Anaplasma marginale, demonstrates higher expression of chemokines and other myeloid cell-associated genes by WC1+ γδ T cells

The functions of gamma delta T cells are enigmatic, and these cells are often considered as evolutionary remnants of well-characterized alpha beta T cells. However, their conservation throughout evolution suggests that gamma delta T cells are biologically unique. In ruminants, gamma delta T cells expressing the workshop cluster 1 (WC1) scavenger receptor comprise a large proportion of circulating lymphocytes, suggesting these cells are biologically relevant and functionally different from or alpha beta T cells. In fact, bovine WC1(+) gamma delta T cells can act as APC for alpha beta T cells, indicating they may express genes encoding proteins associated with innate immunity. The present study was designed to compare immune function gene expression profiles of clonal populations of WC1(+) gamma delta and CD4(+) alpha beta T cells derived from the same animal, which respond to major surface protein 2 (MSP2) of the intraerythrocytic rickettsial pathogen of cattle, Anaplasma murginale. Gene expression profiles of activated T cell clones were compared using a microarray format, and differential gene expression was confirmed by real-time RT-PCR and protein analyses. We demonstrate that although MSP2-specific alpha beta and gamma delta T cell clones express many of the same genes, gamma delta T cell clones express high levels of genes associated with myeloid cells, including chemokines CCL2, CXCL1, CXCL2, CXCL6, and surface receptors CD68, CD11b, macrophage scavenger receptor 1, macrophage mannose receptor, and galectin-3. It is important that many of these genes were also expressed at higher levels in polyclonal WC1(+) gamma delta T cells when compared with CD4(+) alpha beta T cells selected from peripheral blood.