Plasticity of T-cell phenotype and function: the T helper type 17 example

Area of Science:

• Immunology
• Cell Biology
• T-cell Differentiation

Background:

• Established T helper type 1 (Th1) and T helper type 2 (Th2) cells maintain lineage specificity through mutual antagonism.
• The discovery of T helper type 17 (Th17) cells introduces complexity to the Th1/Th2 paradigm, questioning T-cell fate plasticity.
• Previous models suggested Th17 development is inhibited by Th1 and Th2 cells, with reciprocal inhibition between Th17/Th1 and Th17/regulatory T-cell subsets.

Purpose of the Study:

• To review the role of the Th17 subset within the broader context of effector and regulatory T-cell lineages.
• To discuss recent findings that challenge established notions of cross-lineage suppression and T-cell plasticity.
• To explore the implications of Th17 cell plasticity for autoimmunity, cancer, and immunotherapy design.

Main Methods:

• Review of existing literature and recent experimental observations on T-cell differentiation and plasticity.
• Analysis of mechanisms governing Th17 cell polarization, memory formation, and regulatory T-cell conversion.
• Discussion of factors influencing cross-lineage suppression and phenotype switching in T-cell subsets.

Main Results:

• Differentiated Th17 cells are susceptible to polarization towards a Th1 phenotype, supported by Th1 factors like interferon-gamma and T-bet.
• Th1 polarization enhances Th17 memory cell function.
• A subpopulation of regulatory T cells exhibits plasticity, allowing for selective induction into a Th17 phenotype.

Conclusions:

• The plasticity of T-cell differentiation, particularly involving Th17 cells and regulatory T cells, is more dynamic than previously understood.
• Understanding these phenotype shifts is crucial for clarifying T-cell differentiation flexibility and its role in immune-mediated diseases.
• Insights into these mechanisms can guide the development of immunotherapies targeting T-cell responses for autoimmune diseases, cancer, and restoring immune homeostasis.