Memory Phenotype Tfh Cells Develop Without Overt Infection and Support Germinal Center Formation and B Cell Responses...

Area of Science:

• Immunology
• Cell Biology

Background:

• Pathogen-induced T follicular helper (Tfh) cells are crucial for high-affinity antibody production and immunological memory.
• The development and function of Tfh cells in the absence of overt infection were previously unclear.

Purpose of the Study:

• To investigate the existence and characteristics of Tfh cells that develop under pathogen-free conditions.
• To determine the functional capabilities and potential role of these memory phenotype (MP) Tfh cells in immune responses and autoimmunity.

Main Methods:

• Phenotypic and functional characterization of MP Tfh cells in mice, including gene expression analysis (FR4, Egr2).
• In vitro assessment of MP Tfh cell support for B cell IgG production.
• In vivo studies evaluating germinal center formation and antibody responses post-infection.
• Comparison of mouse MP Tfh cells with human circulating Tfh cells in Sjögren's syndrome patients.

Main Results:

• Identified MP Tfh cells expressing FR4 and Egr2, similar to pathogen-induced Tfh cells.
• MP Tfh cells exhibit gene expression related to Tfh development, homeostatic proliferation, and metabolism.
• These cells support B cell IgG production in vitro and promote germinal center formation and antiviral antibodies in vivo.
• Similar phenotypes observed in human circulating Tfh cells, with increased T-bet expression linked to pathology in Sjögren's syndrome.

Conclusions:

• MP Tfh cells develop independently of infection and contribute to protective immune responses.
• Dysregulation of MP Tfh cell activity may be implicated in the pathogenesis of autoimmune diseases like Sjögren's syndrome.