Myeloid-Derived Suppressor Cells (MDSCs)

Definition

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of immune cells that originate from the myeloid lineage and have the ability to suppress T cell responses, contributing to immune evasion in tumors. These cells expand in the presence of tumors and play a significant role in creating an immunosuppressive environment that allows cancer cells to proliferate and evade detection by the immune system. MDSCs can inhibit various immune responses through multiple mechanisms, making them a key player in tumor biology.

5 Must Know Facts For Your Next Test

1. MDSCs can be divided into two main subsets: monocytic MDSCs (M-MDSCs) and granulocytic MDSCs (G-MDSCs), each with distinct mechanisms of action.
2. These cells can produce various immunosuppressive factors, such as arginase-1, inducible nitric oxide synthase (iNOS), and reactive oxygen species (ROS), which inhibit T cell function.
3. MDSCs are often found in elevated numbers in cancer patients and their abundance correlates with disease progression and poor prognosis.
4. One way MDSCs promote tumor growth is by inducing T cell apoptosis or anergy, effectively preventing an effective anti-tumor immune response.
5. Strategies to target or deplete MDSCs are being investigated as potential therapeutic approaches to enhance anti-tumor immunity.

Review Questions

• How do myeloid-derived suppressor cells (MDSCs) impact the effectiveness of anti-tumor immune responses?
  • MDSCs significantly dampen the effectiveness of anti-tumor immune responses by suppressing T cell activation and proliferation. They do this through the release of immunosuppressive factors that create an environment unfavorable for T cell function. By inhibiting T cell activity, MDSCs allow tumors to evade immune detection, facilitating tumor growth and progression.
• Discuss the mechanisms through which MDSCs promote immune evasion in cancer.
  • MDSCs promote immune evasion in cancer through various mechanisms including the secretion of immunosuppressive cytokines, production of reactive oxygen species (ROS), and expression of ligands that engage inhibitory receptors on T cells. They can also induce T cell apoptosis or functional suppression by directly interacting with these cells. By creating an immunosuppressive environment, MDSCs play a critical role in helping tumors escape from immune surveillance.
• Evaluate the potential therapeutic strategies targeting MDSCs in cancer treatment and their implications for improving patient outcomes.
  • Targeting MDSCs presents a promising therapeutic strategy to enhance anti-tumor immunity. Approaches may include depleting MDSCs from circulation, inhibiting their recruitment to tumors, or blocking their immunosuppressive functions. By reducing the number or activity of MDSCs, these strategies aim to restore T cell function and improve patient responses to existing treatments like immunotherapy. Overall, effective targeting of MDSCs could lead to better outcomes for cancer patients by reinvigorating their immune systems against tumors.

Related terms

Tumor Microenvironment: The tumor microenvironment refers to the surrounding cells, signaling molecules, and extracellular matrix that influence tumor growth and immune response.

T Regulatory Cells (Tregs): T regulatory cells (Tregs) are a subset of T cells that help maintain immune tolerance and prevent excessive immune responses, often contributing to tumor immune evasion.

Cytokines: Cytokines are signaling molecules released by cells that mediate and regulate immunity, inflammation, and hematopoiesis, playing a critical role in the interaction between MDSCs and other immune cells.