Adenosinergic regulation of the expansion and immunosuppressive activity of CD11b+Gr1+ cells.

Ryzhov S, Novitskiy SV, Goldstein AE, Biktasova A, Blackburn MR, Biaggioni I, Dikov MM, Feoktistov I
J Immunol. 2011 187 (11): 6120-9

PMID: 22039302 · PMCID: PMC3221925 · DOI:10.4049/jimmunol.1101225

Extracellular adenosine and purine nucleotides are elevated in many pathological situations associated with the expansion of CD11b(+)Gr1(+) myeloid-derived suppressor cells (MDSCs). Therefore, we tested whether adenosinergic pathways play a role in MDSC expansion and functions. We found that A(2B) adenosine receptors on hematopoietic cells play an important role in accumulation of intratumoral CD11b(+)Gr1(high) cells in a mouse Lewis lung carcinoma model in vivo and demonstrated that these receptors promote preferential expansion of the granulocytic CD11b(+)Gr1(high) subset of MDSCs in vitro. Flow cytometry analysis of MDSCs generated from mouse hematopoietic progenitor cells revealed that the CD11b(+)Gr-1(high) subset had the highest levels of CD73 (ecto-5'-nucleotidase) expression (Δmean fluorescence intensity [MFI] of 118.5 ± 16.8), followed by CD11b(+)Gr-1(int) (ΔMFI of 57.9 ± 6.8) and CD11b(+)Gr-1(-/low) (ΔMFI of 12.4 ± 1.0) subsets. Even lower levels of CD73 expression were found on Lewis lung carcinoma tumor cells (ΔMFI of 3.2 ± 0.2). The high levels of CD73 expression in granulocytic CD11b(+)Gr-1(high) cells correlated with high levels of ecto-5'-nucleotidase enzymatic activity. We further demonstrated that the ability of granulocytic MDSCs to suppress CD3/CD28-induced T cell proliferation was significantly facilitated in the presence of the ecto-5'-nucleotidase substrate 5'-AMP. We propose that generation of adenosine by CD73 expressed at high levels on granulocytic MDSCs may promote their expansion and facilitate their immunosuppressive activity.

MeSH Terms (17)

5'-Nucleotidase Adenosine Animals Carcinoma, Lewis Lung CD11b Antigen Cell Differentiation Cell Proliferation Cell Separation Female Flow Cytometry Granulocytes Male Mice Mice, Inbred C57BL Myeloid Cells Real-Time Polymerase Chain Reaction Receptors, Purinergic P1

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