Figure 1. Circulating CXCR5⁺ CD4⁺ T cells expand following transplantation and display phenotypic and functional characteristics of cTfh cells.

(A) Naïve B6 mice were transplanted with skin from either B6 (Syn) or BALB/c (Allo) donors and sacrificed 10 days post-transplantation for PBMC and graft-dLN analysis. (B) Flow cytometric plots (gated on CD4⁺Foxp3⁻ T cells) displaying the frequencies of CXCR5⁺ T cells. (C) Summary data of the frequencies and numbers of cTfh cells (n=5 per group). (D) Representative flow plots (gated on CD4⁺Foxp3⁻ T cells) of blood-derived CXCR5⁺ (PBMC) and graft-dLN Tfh cells as defined by CXCR5 and PD-1. (E) Summary data of phenotypic marker expression by CXCR5⁺ PBMCs and graft-dLN Tfh cells (n=5 per group). (F) Flow plots (gated on CD4⁺Foxp3⁻ T cells) depict gating strategy for naïve (CD44^loCD62L⁺), antigen-experienced (CD44^hiCXCR5⁻) and CXCR5⁺ T cell populations with summary data of phenotypic marker expression by each subset, respectively (n=5 per group). (G) Representative flow plots (gated on CD19⁺IA-IE⁺ B Cells) displaying the frequencies of GC-like B cells following 6-day in vitro T:B cell co-culture from BALB/c transplanted mice. (H) Summary data of the frequencies of IgG⁺GL-7⁺ B cells and total IgG after T:B cell co-culture (n=3 with cells pooled from 5–10 mice). Summary data represent mean (SE) and are representative of 2–4 independent experiments with a total of 10–20 mice per group. *p < 0.05, **p < 0.01, ***p< 0.001.