Stochastic cytokine expression induces mixed T helper cell States

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Cell differentiation is typically driven by lineage-specific transcription factors that repress alternative fates.
• Extracellular signals like cytokines bind receptors, modulating transcription factor activity.
• Understanding T helper cell differentiation into Th1 and Th2 states is crucial for immune response regulation.

Purpose of the Study:

• To investigate the early differentiation dynamics of naive CD4 T helper cells into Th1 versus Th2 states.
• To examine the co-expression patterns of antagonistic transcription factors during T cell differentiation.
• To elucidate the role of extracellular cytokines in overriding intracellular differentiation networks.

Main Methods:

• Single-cell transcript counting to quantify transcription factor expression.
• Immunofluorescence quantification in individual cells to assess protein levels.
• Inhibition of cytokine signaling to observe effects on transcription factor expression.

Main Results:

• Contrary to mutual exclusion, naive CD4 T cells exhibit ubiquitous co-expression of antagonistic Th1 and Th2 transcription factors at high levels.
• Cytokine expression is limited to a small cell subpopulation and is independent of transcription factor expression.
• Inhibition of cytokine signaling leads to the expected mutual exclusion of antagonistic transcription factors.
• Cell-to-cell variation in cytokine expression is significantly higher during early differentiation than in the fully differentiated state.

Conclusions:

• Early CD4 T helper cell differentiation results in a mixed Th1/Th2 state, primarily instructed by extracellular cytokines.
• A weak intracellular network is overruled by strong extracellular cytokine signals during T cell differentiation.
• The interplay between extracellular and intracellular signaling provides a mechanism for mammalian cells to buffer against noisy cytokine expression.