Roles of T Follicular Helper Cells and T Follicular Regulatory Cells in Autoantibody Production in IL-2-Deficient Mice

• Published in: ImmunoHorizons 2019-07, Vol.3 (7), p.306-316
• Main Authors: Xie, Markus M, Liu, Hong, Corn, Caleb, Koh, Byung-Hee, Kaplan, Mark H, Turner, Matthew J, Dent, Alexander L
• Format: Article
• Language: English
• Subjects: Animals; Autoantibodies - biosynthesis; Autoimmunity - immunology; Cell Differentiation; Gene Knockout Techniques; Interleukin-2 - genetics; Interleukin-2 - metabolism; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Knockout; Models, Animal; Myeloid Differentiation Factor 88 - genetics; Proto-Oncogene Proteins c-bcl-6 - genetics; T-Lymphocytes, Helper-Inducer - immunology; T-Lymphocytes, Helper-Inducer - metabolism; T-Lymphocytes, Regulatory - immunology; T-Lymphocytes, Regulatory - metabolism
• ISSN: 2573-7732; 2573-7732
• DOI: 10.4049/immunohorizons.1900034

Autoantibodies can result from excessive T follicular helper (Tfh) cell activity, whereas T follicular regulatory (Tfr) cells negatively regulate autoantibody production. IL-2 knockout (KO) mice on the BALB/c background have elevated Tfh responses, produce autoantibodies, and develop lethal autoimmunity. We analyzed Tfh and Tfr cells in IL-2 KO mice on the C57BL/6 (B6) genetic background. In B6 IL-2 KO mice, the spontaneous formation of Tfh cells and germinal center B cells was greatly enhanced, along with production of anti-DNA autoantibodies. IL-2 has been reported to repress Tfr cell differentiation; however, Tfr cells were not increased over wild-type levels in the B6 IL-2 KO mice. To assess Tfh and Tfr cell regulation of autoantibody production in IL-2 KO mice, we generated IL-2 KO mice with a T cell-specific deletion of the master Tfh cell transcription factor Bcl6. In IL-2 KO Bcl6 conditional KO (2KO-Bcl6TC) mice, Tfh cells, Tfr cells, and germinal center B cells were ablated. In contrast to expectations, autoantibody IgG titers in 2KO-Bcl6TC mice were significantly elevated over autoantibody IgG titers in IL-2 KO mice. Specific deletion of Tfr cells with Foxp3-cre Bcl6-flox alleles in IL-2 KO mice led to early lethality, before high levels of autoantibodies could develop. We found IL-2 Tfr cell-deficient mice produce significant levels of autoantibodies. Our overall findings provide evidence that Tfh cells are dispensable for high-level production of autoantibodies and also reveal a complex interplay between Tfh and Tfr cells in autoantibody production and autoimmune disease.