MALT1 paracaspase is a dual-function protease and scaffold protein central to immune signaling and T cell homeostasis. As a proteolytic enzyme, MALT1 cleaves substrates including BCL10, RC3H1, ROQUIN1/2, and N4BP1 downstream of T cell receptor and pattern recognition receptor activation 123. These cleavage events activate NF-κB and p38 MAPK pathways within CBM (CARD-BCL10-MALT1) complexes, driving pro-inflammatory cytokine production and Th17 cell differentiation 124. MALT1 additionally functions as a ubiquitin ligase activator by binding TRAF6 to oligomerize it 5. Clinically, germline MALT1 deficiency causes an inborn error of immunity characterized by recurrent bacterial, viral, and fungal infections, particularly Staphylococcus aureus and Candida albicans due to impaired Th17 responses 6. Conversely, MALT1 dysregulation drives pathology in lymphomas and solid tumors: gain-of-function CARD11 mutations hyperactivate CARD11-MALT1 signaling and cause hemophagocytic lymphohistiocytosis in dendritic cells 7, while oncogenic MALT1 activity in diffuse large B-cell lymphoma promotes posttranscriptional gene expression via substrate cleavage 8. MALT1 also promotes immune evasion by protecting PD-L1 mRNA through ROQUIN cleavage 9. These dual roles make MALT1 a promising therapeutic target for both immunodeficiency and cancer.