CGRP restrains CD4+ T cell responses and allergic sensitization

Xiaoshi Li¹Ying Zhang¹Wenlong Chen¹Qingren Meng^1,2Ai Huang^1,3Jiayi Pan¹Duan Chen¹Yue Xiao¹Jialin Wei¹Heng Sun^1,4Quan Liu^1*

• ¹Southern University of Science and Technology, Shenzhen, China
• ²Shenzhen University, Shenzhen, China
• ³Huazhong University of Science and Technology, Wuhan, China
• ⁴Chinese Academy of Medical Sciences and Peking Union Medical College, Shenzhen, China

Background: Calcitonin gene-related peptide (CGRP), a neuropeptide released by sensory neurons, plays an emerging role in immune regulation, yet its function in adaptive immunity remains poorly understood. Here, we identify the CGRP–RAMP1 pathway as a key intrinsic regulator of CD4+ T cell responses during allergic sensitization. Methods: Whole-mount imaging and a RAMP1-mCherry reporter system analysed CGRP+ sensory nerve fiber in mediastinal lymph nodes (medLNs) and RAMP1 expression on immune cells. TCR-seq, parabiosis, and adaptive transfer methods were employed to assess the effects of RAMP1 expression in CD4+ T cells. In vitro, CD4+ T cells were stimulated and differentiated, followed by flow cytometry, ATAC-seq, and RNA-seq to evaluate the impact of CGRP. A house dust mite (HDM)-induced allergic sensitization model was used to study CGRP distribution in medLNs. CD4+ T cell-specific RAMP1 knockout mice and CGRP treatment were used to evaluate immune cell infiltration and Tfh responses in allergic sensitization. Additionally, Calca, Ramp1, and CD4+ T cell-specific RAMP1 knockout mouse models were used in the HDM-induced allergic asthma study, with CGRP treatment during the sensitization phase to evaluate its effects on asthma. Results: CGRP+ fibers densely innervate medLNs and that RAMP1 is preferentially expressed on naïve CD4+ T cells. While RAMP1 does not affect thymocyte development, TCR diversity, or tissue residency, CGRP–RAMP1 signalling supresses CD4+ T cell activation and differentiation. CGRP reshapes chromatin accessibility and transcriptional programs to enforce a hyporesponsive state and repress Tfh-associated gene expression. In vivo, the density of CGRP+ fibers is reduced following allergen sensitization. CD4+ T cell-specific RAMP1 deficiency promotes Tfh cell accumulation, enhances B cell activation, and exacerbates allergic sensitization. Conversely, exogenous CGRP treatment attenuates Tfh cell accumulation and mitigates allergic sensitization in a RAMP1-dependent manner. CGRP treatment during the sensitization phase effectively alleviates allergic asthma. Conclusions: These findings suggest a neuroimmune axis in which CGRP–RAMP1 pathway restrains allergic sensitization by directly modulating the immunobiology of CD4+ T cells.