The central message of the review is that Tfh cells are not a monolithic population. Instead, they display profound heterogeneity along two major axes: spatial distribution and phenotypic characteristics. Spatially, researchers now distinguish germinal center-resident Tfh cells, follicular mantle Tfh cells, circulating Tfh cells found in the bloodstream, and peripheral Tfh cells that populate inflamed tissues and tertiary lymphoid structures. Phenotypically, Tfh cells can be further subdivided into Tfh1, Tfh2, and Tfh17 subsets, each defined by distinct cytokine profiles and transcription factor dependencies. This layered diversity allows the immune system to tailor antibody responses to vastly different challenges, from acute viral infections to parasitic worms, but it also creates multiple points at which regulation can fail and pathology can emerge.

At the heart of Tfh cell differentiation lies a transcriptional tug-of-war between two master regulators: B-cell lymphoma 6, or Bcl-6, and cellular musculoaponeurotic fibrosarcoma oncogene homolog, better known as c-Maf. Bcl-6 is the lineage-defining factor that drives nascent CD4 T cells toward the follicular helper fate, enabling them to upregulate the chemokine receptor CXCR5, which guides their migration into B cell follicles, and to suppress alternative differentiation programs. Bcl-6 and its antagonist Blimp-1 form a reciprocal regulatory circuit: high Bcl-6 and low Blimp-1 favor Tfh commitment, whereas the opposite pattern pushes cells toward other effector fates. c-Maf, induced downstream of the costimulatory receptor ICOS, cooperates with Bcl-6 to promote expression of interleukin-21, the signature cytokine through which Tfh cells deliver help to B cells. Together, these factors orchestrate a gene expression program that is both robust and exquisitely sensitive to environmental cues.

That sensitivity is embodied by the cytokine milieu encountered during T cell priming. Interleukin-6, signaling through STAT1 and STAT3, promotes early Bcl-6 induction and Tfh differentiation, while interleukin-12 and type I interferons steer cells toward Tfh1-like phenotypes characterized by the transcription factor T-bet. Conversely, interleukin-2 acts as a brake: high IL-2 signaling through the mTORC1 pathway antagonizes Tfh differentiation, which is why IL-6-mediated suppression of IL-2 responsiveness is required for germinal center Tfh cells to emerge. Interleukin-4 and the transcription factors GATA3, Batf, and STAT6 define the Tfh2 compartment, whereas transforming growth factor-beta, acting through c-Maf and STAT3-STAT4 cooperation, can promote human Tfh differentiation and specify Tfh versus Th17 fates. Additional players such as Ascl2, Tox2, and the chromatin organizer SATB1 fine-tune chromatin accessibility and gene expression, while the kinase mTORC1 and extracellular matrix protein 1 further modulate the process.

The spatial dimension of Tfh biology has emerged as a particularly active research frontier. Landmark studies using intravital microscopy revealed that germinal center Tfh cells are highly motile, dynamically interacting with B cells in a competitive process that shapes antibody affinity maturation. Development of both germinal center B cells and Tfh cells initiates in the interfollicular zone, where antigen-presenting dendritic cells first license naive T cells before they migrate into follicles. Within germinal centers themselves, progressively differentiated Tfh subsets have been described, and recent work has identified physiologically distinct CXCR5-high, PD-1-high resident populations. Long-lived memory Tfh cells, which persist after infection or vaccination and retain remarkable plasticity, sustain humoral immunity for years, and memory-like Tfh subsets have been identified as precursors of effector Tfh cells during recall responses. Circulating CXCR5-positive CD4 T cells in human blood mirror these lymphoid tissue counterparts and contain subsets that differentially support antibody secretion, providing a convenient window into systemic humoral immunity.

The clinical significance of this heterogeneity becomes stark when Tfh subsets go awry. In viral infections, Tfh1 cells dominated by T-bet and STAT4 are critical for generating neutralizing antibodies against influenza, HIV, and SARS-CoV-2, and circulating Tfh responses in recovered COVID-19 patients have been correlated with durable antibody titers. Yet in autoimmune diseases, the very same differentiation programs can become pathological. In systemic lupus erythematosus, aberrant expansion of multiple Tfh subsets, including IL-17-producing and IL-4-producing populations, drives autoantibody production and nephritis, while T peripheral helper cells, a closely related CXCR5-negative population sharing the transcription factor c-Maf, promote B cell activation through MAF and IL-21. In rheumatoid arthritis, pathologically expanded peripheral T helper cells drive B cell responses in inflamed synovium, and STAT3 hyperactivation associates with disease activity. IgG4-related disease has been linked to CCR4-positive Tfh2 cells producing interleukin-4, and food allergy involves Tfh-derived programs that promote anaphylactic IgE, including a distinct Tfh13 subset stabilized by JunB.

Cancer adds yet another layer of complexity, because Tfh cells can play contradictory roles depending on context. Within tertiary lymphoid structures, the ectopic lymphoid aggregates that form inside tumors, Tfh cells collaborate with B cells to generate anti-tumor antibody-producing plasma cells, and neoantigen-driven collaboration between B cells and CD4 Tfh cells promotes cytotoxic CD8 T cell responses. Th1-oriented Tfh cells infiltrating breast cancer correlate with effective adaptive immunity, and microbiota-specific Tfh cells drive tertiary lymphoid structures and anti-tumor immunity in colorectal cancer. However, pro-tumor Tfh2 cells in pancreatic cancer induce detrimental IgG4 production, elevated IgG4 in melanoma patients is associated with disease progression, and regulatory T cells within tumor-associated tertiary lymphoid structures can suppress anti-tumor responses. VISTA-positive follicular regulatory T cells have been implicated in immune escape in ovarian cancer, making the Tfh-Tfr axis a potential target for combination immunotherapy.

Counterbalancing the helper activity of Tfh cells is a dedicated regulatory population: the T follicular regulatory cell, or Tfr cell. These Foxp3-positive and Bcl-6-positive cells suppress germinal center reactions, restrain cytokine production by Tfh cells, and optimize the quality of IgG responses. Tfr cells can be antigen-specific, derive from naive T cells, and even share clonal relationships with Tfh cells, with human Tfh clones shown to seed the germinal center-resident regulatory pool. Their stability and progressive differentiation are controlled by Tfh programs themselves. Mechanistically, Tfr cells deploy CTLA-4, PD-1, interleukin-10, and the neurotrophic factor neuritin to modulate B cell and T cell function, while the IL-2-mTORC1 axis and the transcription factors Bach2 and NFAT2 govern their development. Restoring the Tfr-to-Tfh balance has shown therapeutic promise in lupus nephritis models and in low-dose IL-2 trials for active SLE, and Tfr cells have been shown to restrain kidney allograft rejection by suppressing alloreactive B cells.

The translational implications of this work are already visible. The CD40 ligand antagonist dazodalibep has shown efficacy in a phase 2 trial for Sjogren’s disease, small molecules such as niclosamide and artesunate suppress Tfh expansion through STAT3 and JAK2-STAT3 pathways in lupus models, and OX40L-JAG1 cotreatment has restored follicular regulatory-helper balance in mice. As the Beijing Normal University team argues, integrating the multiple Tfh subsets into a unified systematic framework provides a new perspective for understanding humoral immune regulation and for developing targeted therapies that selectively boost protective antibody responses during infection and vaccination while dampening the pathological helper activity that fuels autoimmunity, allergy, and certain cancers. In an era when mRNA vaccines, checkpoint inhibitors, and CAR-T therapies all depend on or interact with the humoral arm of immunity, deciphering the rules that govern Tfh subset differentiation may prove to be one of immunology’s most consequential endeavors.

Subject of Research: Regulation of follicular helper T cell subset differentiation in humoral immunity, infection, autoimmunity, and cancer

Article Title: Regulation of follicular helper T cell subset differentiation in health and disease

Article References: Xin, Q., Zhao, L., Zhang, J., Liu, X., & Liu, G. (2026). Regulation of follicular helper T cell subset differentiation in health and disease. Journal of Molecular Medicine, 104(1), Article 115. https://doi.org/10.1007/s00109-026-02721-6

Image Credits: AI Generated

DOI: 10.1007/s00109-026-02721-6

Keywords: T follicular helper cells, germinal centers, Bcl-6, c-Maf, B cell help, antibody responses, autoimmunity, systemic lupus erythematosus, T follicular regulatory cells, tertiary lymphoid structures, cancer immunology, viral infection