Expansion of Peripheral Extra-Follicular Helper T Cells in Patients with Chronic Graft-Versus-Host Disease

Introduction:

Chronic graft-versus-host disease (cGVHD) is a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (allo-HCT). In contrast to acute GVHD, cGVHD is an autoimmune-like syndrome. The clinical manifestations of cGVHD are highly variable, including skin pathology varying from lichen planus-like lesions to full sclerosis, oral lichen planus-like lesions, muscle or joint fasciitis, and bronchiolitis obliterans (BO) (Bruce Blazar et. al. Blood 2016). Recently, extrafollicular CD4⁺ T- and B- cell interactions are gaining more and more attentions in the pathogenesis of autoimmune diseases. It has been reported that mice with cGVHD had an expansion of extrafollicular CD4⁺ T cells (Ruishu D et. al. Nature communications 2017). It is still unclear whether extrafollicular CD4⁺ T helper cells play an important role in the development of human cGVHD or not.

Methods:

A total of 70 patients with hematologic malignancies who underwent allo-HSCT at Nanfang Hospital between June 2015 and June 2017 were enrolled in this experimental study. The diagnosis and grade of cGVHD was made at the time of sample collection according to National Institutes of Health criteria (Howard M.S. et. al. BBMT 2015). Comparison of three means was analyzed using a one-way ANOVA test. Comparison of two means was analyzed using an unpaired two-tailed Student t-test. Correlation studies were performed using the Pearson correlation coefficient test.

Results:

We found that the frequency and count of circulating T follicular helper cells (cTfh) markedly decreased in patients with active cGVHD compared with patients without cGVHD (median, 3.16% vs 1.19% of CD4⁺ T cells; P <0.0001 and median,11.26 x10^⁶ vs 1.77 x10^⁶; P <0.0001). These decreases are more significant in patients with moderate/severe cGVHD. We further found that the frequency of extrafollicular CD4⁺ T cells in patients with active cGVHD significantly increased (median, 3.93% vs 8.69% of CD4⁺ T cells; P <0.001). There was also an increased trend in the count of extrafollicular CD4⁺ T cells of patients with active cGVHD, although patients with active cGVHD have lymphopenia (median, 6.91 x10^⁶ vs 13.20 x10^⁶; P =0.19). Multivariable linear regression analysis confirmed that active cGVHD was a significant factor for high percentage of extrafollicular CD4⁺ T cells after adjusting for other transplant characteristics (P <0.001). Moreover, expansion of extrafollicular CD4⁺ T cells correlated with the clinical grade of cGVHD (P <0 .005), and the difference lasted until 1 year after allo-HCT. The expansion of extrafollicular CD4⁺ T cells was highly correlated with the generation of IgG1 antibodies (P <0 .05).

Conclusions:

These results demonstrate that expansion of extrafollicular CD4⁺ T cells plays a critical role in the pathogenesis of human cGVHD. Targeting extrafollicular CD4⁺ T-B-cell interactions may be an effective strategy in patients with cGVHD.