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Immunosuppressive assays

MDSC Immunosuppressive Assays

The tumor microenvironment has been found to be highly immunosuppressive, and there are many mechanisms responsible for it. Myeloid-derived inhibitory cells (MDSCs) are macrophage-like cells that have acquired an immunosuppressive phenotype by the tumor microenvironment and are known to suppress tumor-directed T cell activity.


Horizon has developed an assay to induce MDSCs to differentiate and inhibit T cell proliferation. Test the ability of the compound to reduce the ability of MDSC to suppress T cells and increase T cell activity.

How do you perform an MDSC immunosuppressive assay?

  • Stimulates PBMCs with cytokine cocktails containing GM-CSF and IL-6 to induce MDSC differentiation
  • CD33-positive cells were isolated and MDSC was recovered
  • Autologous T cells incubated with CD33-positive MDSCs and stimulated with anti-CD3/CD28 antibodies
  • Measurement endpoint: T cell proliferation and activation surface markers

What can be observed from the MDSC immunosuppressive assay?

Peripheral blood-derived monocytes can be efficiently differentiated into myeloid-derived suppressive cells using a cytokine cocktail containing GM-CSF and IL-6 and are enriched using CD33 as a marker (see figure).


CD33-positive MDSCs can be co-cultured with autologous CD8-positive T cells to measure their inhibitory effects.


Cytokine-induced MDSCs (red or blue) were shown to inhibit the proliferation of autologous CD8-positive T cells in a dose-dependent manner compared to CD8-positive T cells alone (green).


In cultures of CD8-positive T cells alone, 20% of T cells do not proliferate, but the addition of MDSCs to the culture increases the proportion of undifferentiated cells in a dose-dependent manner.


The ability of a compound to reduce T cell inhibition can be evaluated.


Treg immunosuppressive assays

Tumors upregulate immune checkpoint molecules such as PD-L1 at the cell surface to inhibit T cell activity, but the immunosuppressive tumor microenvironment can also polarize T cells into inhibitory phenotypes known as regulatory T cells or Tregs. Tregs are CD4-positive T cells characterized by the secretion of the regulatory cytokine IL-10, which inhibits both macrophages and T cells, and suppresses tumor-directed T cell activity.


Horizon has developed an assay that reliably generates Tregs and measures the T cell staticizing capacity of Tregs. Test compounds that modulate Treg polarization or reverse the suppression of T cell proliferation, i.e., increase tumor-directed T cell activity.


How do you perform a Treg immunosuppressive assay?

Stimulates CD4-positive T cells with a cytokine cocktail containing IL-2 and TGF-β1 to induce Treg polarization

Tregs are incubated with effectorT cells (Teff) and stimulated with anti-CD3/CD28 antibodies

Measurement endpoints: Treg polarization and T cell proliferation

Add the compound in either Step 1 (Measure the effect on Treg polarization) or Step 2 (Measure the effect on T cell suppression)