Myeloid derived suppressor cells potentiate virus-specific memory CD8+ T cell response

How therapeutically administered myeloid derived suppressor cells (MDSCs) modulate differentiation of virus-specific CD8+ T cell was investigated. In vitro generated MDSCs from bone marrow precursors inhibited the expansion of stimulated CD8+ T cells but the effector cells in the recipients of MDSCs showed preferential memory transition during Influenza A virus (IAV) or an α- (Herpes Simplex Virus) as well as a γ- (murine herpesvirus 68) herpesvirus infection. Memory CD8+ T cells thus generated constituted a heterogenous population with a large fraction showing effector memory (CD62LloCCR7-) phenotype. Such cells could be efficiently recalled in the rechallenged animals and controlled the secondary infection better. Memory potentiating effects of MDSCs occurred irrespective of the clonality of the responding CD8+ T cells as well as the nature of infecting viruses. Compared to the MDSCs recipients, effector cells of MDSCs recipients showed higher expression of molecules known to drive cellular survival (IL-7R, Bcl2) and memory formation (Tcf7, Id3, eomesodermin). Therapeutically administered MDSCs not only mitigated the tissue damaging response during a resolving IAV infection but also promoted the differentiation of functional memory CD8+ T cells. Therefore, MDSCs therapy could be useful in managing virus-induced immunopathological reactions without compromising immunological memory.