Havcr2, also known as TIM-3 (T cell immunoglobulin and mucin domain 3), encodes a protein that acts as a negative regulator on the surface of Th1 cells, binding to ligands like galectin-9 to mediate Th1 cell apoptosis. It is also expressed on other immune cells such as macrophages, dendritic cells, and monocytes, and has additional ligands including Psdter, HMGB1, and Ceacam-1, playing important roles in autoimmune diseases, chronic viral infections, and tumors [2].

Germline Havcr2 mutations have been associated with subcutaneous panniculitis-like T-cell lymphoma (SPTCL) leading to Hemophagocytic lymphohistiocytosis (HLH), and can cause HLH even without lymphoma [1]. A male patient with a homozygous c.245 A > G p.Tyr82Cys pathogenic variant in Havcr2 suffered from recurrent myocarditis, with unrestrained T cell proliferation and high TLR4-mediated interleukin-1β (IL-1β) response [3]. In a multicenter study, male sex, heterozygous and homozygous/compound heterozygous Havcr2 mutations were associated with an increased risk of developing HLH, and younger patients tended to manifest with HLH while older patients with SPTCL [4]. Ruxolitinib, targeting inflammatory cytokines, showed excellent efficacy in patients with Havcr2-associated HLH and panniculitis manifestations, suggesting an inflammatory rather than neoplastic nature of the disease [5].

In conclusion, Havcr2 plays a crucial role in immune regulation, especially in diseases like HLH, SPTCL, and myocarditis. Studies on Havcr2-associated mutations in patients help to understand its role in disease development, and the response to drugs like ruxolitinib provides new treatment strategies for these diseases.

References:

1. Song, Deli, Wang, Jingshi, Zhang, Jia, Wu, Chaofan, Wang, Zhao. 2023. Case Report: HAVCR2 mutation-associated Hemophagocytic lymphohistiocytosis. In Frontiers in immunology, 14, 1271324. doi:10.3389/fimmu.2023.1271324. https://pubmed.ncbi.nlm.nih.gov/38077348/

2. Zhao, Lizhen, Cheng, Shaoyun, Fan, Lin, Zhang, Bei, Xu, Shengwei. 2021. TIM-3: An update on immunotherapy. In International immunopharmacology, 99, 107933. doi:10.1016/j.intimp.2021.107933. https://pubmed.ncbi.nlm.nih.gov/34224993/

3. Pernaa, Nora, Vakkuri, Anni, Arvonen, Miika, Åström, Pirjo, Hautala, Timo. 2024. Germline HAVCR2/TIM-3 Checkpoint Inhibitor Receptor Deficiency in Recurrent Autoinflammatory Myocarditis. In Journal of clinical immunology, 44, 81. doi:10.1007/s10875-024-01685-x. https://pubmed.ncbi.nlm.nih.gov/38485795/

4. Moonla, Chatphatai, Polprasert, Chantana, Komvilaisak, Patcharee, Sosothikul, Darintr, Rojnuckarin, Ponlapat. 2023. Germline HAVCR2 mutations and their relation to the clinical spectrum of subcutaneous panniculitis-like T-cell lymphoma and hemophagocytic lymphohistiocytosis: results from a multicenter study and meta-analysis. In Haematologica, 108, 2743-2752. doi:10.3324/haematol.2022.282419. https://pubmed.ncbi.nlm.nih.gov/37051767/

5. Zhang, Qing, Zhou, Chun-Ju, Li, Dan-Hong, Duan, Yan-Long, Zhang, Rui. 2023. Efficacy of ruxolitinib for HAVCR2 mutation-associated hemophagocytic lymphohistiocytosis and panniculitis manifestations in children. In British journal of haematology, 202, 135-146. doi:10.1111/bjh.18817. https://pubmed.ncbi.nlm.nih.gov/37062931/