Abstract
The ectoenzymes CD39 and CD73 play a major role in controlling tissue inflammation by regulating the balance between adenosine triphosphate (ATP) and adenosine. Still, little is known about the role of these two enzymes and ATP and its metabolites in the pathophysiology of inflammatory bowel disease (IBD). We isolated mononuclear cells from peripheral blood and lamina propria of the large intestine of patients diagnosed with IBD and of healthy volunteers. We then comprehensively analyzed the CD39 and CD73 expression patterns together with markers of activation (HLA-DR, CD38), differentiation (CCR7, CD45RA) and tissue-residency (CD69, CD103, CD49a) on CD4+, CD8+, γδ+ T cells and mucosa-associated invariant T cells using flow cytometry. CD39 expression levels of γδ+ and CD8+ T cells in lamina propria lymphocytes (LPL) were much higher compared to peripheral blood mononuclear cells. Moreover, the frequency of CD39+ CD4+ and CD8+, but not γδ+ LPL positively correlated with T-cell activation. The frequency of CD39+ cells among tissue-resident memory LPL (Trm) was higher compared to non-Trm for all subsets, confirming that CD39 is a marker for the tissue-resident memory phenotype. γδ+ Trm also showed a distinct cytokine profile upon stimulation - the frequency of IFN-γ+ and IL-17A+ cells was significantly lower in γδ+ Trm compared to non-Trm. Interestingly, we observed a decreased frequency of CD39+ γδ+ T cells in IBD patients compared to healthy controls (p = 0.0049). Prospective studies need to elucidate the exact role of this novel CD39+ γδ+ T-cell population with tissue-resident memory phenotype and its possible contribution to the pathogenesis of IBD and other inflammatory disorders.