Clonal Expansions of CD8(+) T Cells with IL-10 Secreting Capacity Occur during Chronic Mycobacterium tuberculosis Infection

Cyktor, Joshua C.; Carruthers, Bridget; Beamer, Gillian L.; Turner, Joanne

CD8 + T cells from Mtb-infected CBA/J mice are capable of secreting IL-10 CD8 + and CD8 neg cells were purified from the lungs of Mtbinfected CBA/J and C57BL/6 mice and cultured in IL-10 ELISpot plates for 72 hours with autologous bone marrow-derived dendritic cells (BMDCs) that had been infected with Mtb for 24 hours, in the presence or absence of anti-CD3 and anti-CD28. CD8 + cells from CBA/J mice, and not C57BL/6 mice, were capable of secreting IL-10 in response to TcR cross-linking (Fig. 3a) . In contrast, CD8 neg cells from both mouse strains were capable of secreting IL-10 under these same conditions (Fig. 3b) . IL-10-secreting CD8 neg cells were predominantly CD4 + as adherent cells were removed during cell purification and we have failed to detect IL-10 within B cells and neutrophils in both mouse strains (not shown). We also observed that CD8 + T cells from CBA/J and C57BL/6 mice were capable of secreting IFN-c under the same culture conditions (measured in the IL-10 ELISPOT supernatants) (Fig. 3c) . Culture of purified CD8 + and CD8 neg cells from Mtb infected CBA/J mice with Mtb-infected BMDCs in the absence of TcR cross-linking, indicative of an Mtb-specific response, resulted in the secretion of IL-10 from both CD8 neg and CD8 + cells (Fig. 3d) . Interestingly, the capacity of CD8 + T cells to produce IL-10 increased over time, in parallel to the increasing CFU and CD8 + T cell numbers in the lung. The low SFU, relative to TcR cross-linking likely reflects the challenges of delivering of Mtb antigen into the appropriate processing pathway for presentation to CD8 + T cells.