Circulating Follicular Helper and Follicular Regulatory T Cells Are Severely Compromised in Human CD40 Deficiency: A Case Report

• Main Authors: Maria Pia Cicalese, Jolanda Gerosa, Manuela Baronio, Davide Montin, Francesco Licciardi, Annarosa Soresina, Rosa Maria Dellepiane, Maurizio Miano, Lucia Augusta Baselli, Stefano Volpi, Carlo Dufour, Alessandro Plebani, Alessandro Aiuti, Vassilios Lougaris, Georgia Fousteri
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2018-08-01
• Series: Frontiers in Immunology
• Subjects: hyper-IgM syndrome; follicular helper T cells; follicular regulatory T cells; class switch recombination; somatic hypermutation; AICDA
• Online Access: https://www.frontiersin.org/article/10.3389/fimmu.2018.01761/full

Mutations in genes that control class switch recombination and somatic hypermutation during the germinal center (GC) response can cause diverse immune dysfunctions. In particular, mutations in CD40LG, CD40, AICDA, or UNG cause hyper-IgM (HIGM) syndrome, a heterogeneous group of primary immunodeficiencies. Follicular helper (Tfh) and follicular regulatory (Tfr) T cells play a key role in the formation and regulation of GCs, but their role in HIGM pathogenesis is still limited. Here, we found that compared to CD40 ligand (CD40L)- and activation-induced cytidine deaminase (AICDA)-deficient patients, circulating Tfh and Tfr cells were severely compromised in terms of frequency and activation phenotype in a child with CD40 deficiency. These findings offer useful insight for human Tfh biology, with potential implications for understanding the molecular basis of HIGM syndrome caused by mutations in CD40.