Tirap, also known as Toll-interleukin-1 Receptor (TIR) domain-containing adaptor protein (TIRAP) or MAL, is a key intracellular signalling molecule regulating diverse immune responses [1,3]. It functions as an adaptor in Toll-like Receptor (TLR)-mediated innate immune signalling, mainly in the MyD88-dependent TLR signalling pathway, such as through TLR2 and TLR4 [1,4]. It also interacts with non-TLR signalling mediators, indicating its central role in various immune responses [1].

In a mouse model, Tirap heterozygous mice were more resistant to Mycobacterium tuberculosis (Mtb) infection compared to wild-type littermates. Mtb infection induced Tirap expression, which prevented phagosomal acidification and rupture, and the Tirap-mediated anti-tuberculosis effect occurred through a Cish-dependent signalling pathway [2]. In another study, overexpression of TIRAP in various types of myelodysplastic syndromes (MDS) suppressed all three major hematopoietic lineages. TIRAP expression promoted up-regulation of Ifnγ, leading to myelosuppression through Ifnγ-Ifnγr-mediated release of Hmgb1, which disrupted the bone marrow endothelial niche. Deletion of Ifnγ reversed the endothelial defect and restored myelopoiesis [5].

In conclusion, Tirap plays a crucial role in immune responses, especially in TLR-mediated signalling. Model-based research, such as gene-modified mouse models, has revealed its significance in diseases like tuberculosis and myelodysplastic syndromes. Understanding Tirap's functions provides insights into the pathophysiology of these diseases and may offer potential therapeutic targets.