Regulatory T Cells

Regulatory T cells are a heterogeneous subset of CD4+ T cells with suppressive properties that play a central role in maintaining CD4+ and CD8+ effector T cells, natural killer cells, NKT cells, and antigen-presenting cells through multiple mechanisms including the secretion of  immunosuppressive cytokines (IL-10, IL-35, and TGF-b) and metabolites (Adenosine), production of cytolytic factors (Granzymes A/B and Perforin), disruption of cell metabolism (i.e. IL-2 deprivation), and suppression of effector functions through direct cell-cell contact.

Several subsets of regulatory T cells exist. These include naturally occurring CD4+CD25+FoxP3+ cells that develop in the thymus, peripherally-derived regulatory T cells that are generated from FoxP3- conventional T cells at sites outside of the thymus, and induced regulatory T cells that are generated in vitro by stimulation of mouse conventional T cells with TGF-b.

Cells in the peripheral group have been further classified as either central regulatory T cells, effector regulatory T cells, or tissue-resident regulatory T cells. Additionally, CD4+FoxP3− type I regulatory T cells (Tr1), CD8+ regulatory T cells, and follicular regulatory T cells (TFR) have been described. Characteristics that distinguish these subsets as well as differences in their development and functional activity are active areas of investigation.

There are several mechanisms by which regulatory T cells control the activity of other immune cells types. These include:

• Secretion of TGF, IL-10, IL-35 and Galectin-1
• Inhibits the differentiation, proliferation and activation of effector T cells
• Suppresses cytokine production by effector T cells
• IL-35 and TGF-b1 induce IL-10 production and regulate FoxP3 expression, promoting the maintenance and expansion of CD4+CD25+ Regulatory T  cells

• Membrane-associated LAP-TGF-b1 (Latent TGF-b1)
• Cell surface LAP-TGF-b1 (latent TGF-b1), complexed with LRRC32, suppresses the proliferation of activated Effector T  cells
  
  
• High Levels of CD25/IL-2 Ra Expression
• Depletes local IL-2, inhibiting activation and proliferation of effector T cells
• IL-2 maintains CD4+CD25+ Regulatory T  cell populations

• Generation of Extracellular Adenosine by Cell Surface Expression of CD39/CD73
• Activation of A2A receptors by Adenosine blocks the expression of costimulatory molecules and growth factor receptors in Effector T  cells, inhibiting Effector T  cell activation, proliferation, and expansion
  
  
• Transfer of Inhibitory cAMP through Gap Junctions
• Inhibits Effector T  cell proliferation and IL-2 gene expression
  
  
• Membrane-associated Galectin-1
• Binds to GM1 ganglioside on Effector T cells
• Induces cross-linking of associated integrins, triggering
• TRPC5 channel activation and calcium influx, inhibiting
• Effector T cell proliferation
  
  
• Induction of Infectious Tolerance
• In mice, membrane-associated LAP-TGF-b1 converts non-Regulatory T  cells into functional, FoxP3-expressing Regulatory T cells
  
  
• Granzyme A/B Secretion
• Granzyme A/B induces apoptosis in DCs and Effector T  cells in both a perforin-dependent and -independent manner
  
  
• Binding of LAG-3 to MHC II
• Induces an immunoreceptor tyrosine-based activation motif (ITAM)-mediated inhibitory signaling pathway, blocking the maturation and immunostimulatory capacity of DCs
  
  
• CTLA-4-dependent Suppression
• CTLA-4 interacts with B7 (CD80 and CD86) on DCs, triggering indoleamine 2, 3- dioxygenase (IDO) expression (which is also induced by IFN-g receptor stimulation)
• IDO catabolizes tryptophan, depleting stores needed for Effector T  cell proliferation, and producing the pro-apoptotic metabolite Ν-formylkynurenine

Human Treg Cell Differentiation Kit
Differentiates naïve CD4+ human lymphocytes into CD25+FoxP3+ regulatory T cells.

Mouse Treg Cell Differentiation Kit
Differentiates naïve CD4+ mouse lymphocytes into CD25+FoxP3+ regulatory T cells.

Cell Activation Reagents

Cell Activation Cocktail
A 500X cocktail of Monensin, PMA, and Ionomycin for activating immune cells.

Resources for in vitro Differentiation and Expansion: