Programmed Death 1 and Cytokine Inducible SH2-Containing Protein Dependent Expansion of Regulatory T Cells Upon Stimulation With Mycobacterium tuberculosis

We previously found that CD4+CD25+FoxP3+ regulatory T cells (Tregs) expand in response to Mycobacterium tuberculosis infection in individuals who are healthy tuberculin reactors, but not in tuberculin-negative individuals. We also found that the M. tuberculosis mannose-capped lipoarabinomannan and prostaglandin E2 produced by monocytes are involved in Treg expansion. In this study, we found that Tregs expanded from CD4+CCR4+ cells but not from CCR4− cells. However, introduction of CCR4 small interfering RNA (siRNA) into CD4+ cells only marginally reduced expansion of Tregs. Using siRNA and neutralizing antibodies, we found that expansion of Tregs by M. tuberculosis required expression of programmed death1 (PD-1) and expression of the signaling molecule, cytokine inducible SH2-containing protein (CISH). Anti-PD-1 siRNA inhibited expression of CISH by expanded Tregs. M. tuberculosis–expanded Tregs produced transforming growth factor β and interleukin 10 and reduced the frequency of interferon γ–producing autologous CD8+ cells. We conclude that M. tuberculosis infection induces development of Tregs from CCR4+ cells through a process that depends on PD-1and CISH.