T Cells That Help B Cells in Chronically Inflamed Tissues

Area of Science:

• Immunology
• Cell Biology
• Pathology

Background:

• Chronically inflamed tissues often contain lymphocyte aggregates that support T cell-B cell interactions.
• These structures can range from simple clusters to organized ectopic lymphoid structures, sometimes featuring germinal centers with T follicular helper (Tfh) cells.

Purpose of the Study:

• To review observations of T cell populations interacting with B cells in chronically inflamed tissues.
• To highlight differences between these tissue-infiltrating T cells and prototypical Tfh cells.
• To discuss the role of T peripheral helper (Tph) cells in rheumatoid arthritis.

Main Methods:

• Review of existing literature and disease models.
• Analysis of surface phenotypes, migratory capacity, and transcriptional regulation of T cells in inflamed tissues.
• Focus on specific cell populations like Tph cells and their associated molecules (e.g., PD-1, CXCR5, Bcl6, CXCL13, IL-21).

Main Results:

• In many inflamed tissues, T cells interacting with B cells differ significantly from Tfh cells.
• Tissue-infiltrating T cells can produce B cell-helping factors like IL-21 and CXCL13.
• The T peripheral helper (Tph) cell population (PD-1hi CXCR5- Bcl6low) in rheumatoid arthritis infiltrates synovium and enhances B cell responses.

Conclusions:

• Diverse CD4+ T cell populations, beyond Tfh cells, can provide help to B cells in inflamed tissues.
• Understanding these varied T cell subsets is crucial for diagnosing and treating inflammatory conditions.
• This knowledge can inform therapeutic strategies targeting B cell-helper T cells.