Abstracts (complete list) - Wissenschaft Online

Ioanna Galani, Marco Wendel, Carola Schellack, Elisabeth Suri-Payer, Adelheid
Cerwenka
REGULATORY T CELLS SUPPRESS IFN-γ DEPENDENT
LEUKOCYTE ACCUMULATION AND MACROPHAGE ACTIVATION
IN LYMPHOMA
Regulatory T cells (Treg) have been shown to suppress immune responses of tumorspecific
T cells; yet, little is known about the impact of Treg on innate immune cells in
tumor models. Since many tumors lose expression of MHC class I, our study aimed at
defining strategies to strengthen immune responses against a high tumor burden of the
MHC class I-deficient lymphoma RMA-S. We demonstrate that Treg depletion led to
tumor rejection and generation of immunological memory. This tumor rejection was
associated with a substantial, IFN-γ dependent increase in numbers of tumor-infiltrating
leukocytes, including macrophages. Tumor-infiltrating macrophages from Treg depleted
mice expressed increased amounts of MHC class II, produced enhanced levels of
inflammatory cytokines and inhibited tumor cell proliferation. Our study reveals that in
an in vivo tumor model, numbers and activity of macrophages are controlled by Treg.
These data identify macrophages as novel targets for Treg mediated immune
suppression in cancer.