Complement factor B (CFB) is a circulating serine protease that plays a central role in the alternative pathway of the complement system, a critical component of innate immunity. Encoded by the CFB gene, this protein is primarily synthesized by hepatocytes, adipocytes, and monocytes, reflecting its systemic and local involvement in immune surveillance and inflammation ^[1]. Upon activation by factor D, CFB forms the active enzyme factor Bb, which, in complex with complement component C3b, constitutes the alternative pathway C3 convertase (C3bBb). This convertase catalyzes the cleavage of C3 into the anaphylatoxin C3a and the opsonin C3b, leading to the amplification of the complement cascade and the subsequent elimination of pathogens and damaged cells ^[2]. Dysregulation of CFB activity, often stemming from genetic polymorphisms within the CFB locus, has been implicated in the pathogenesis of several human diseases, including age-related macular degeneration (AMD), atypical hemolytic uremic syndrome (aHUS), and systemic lupus erythematosus (SLE), underscoring the delicate balance required for proper complement regulation and immune homeostasis ^[3-4]. These associations highlight CFB as a key mediator of both protective and pathological immune responses.

The MASP2 gene encodes MASP-2, a serum serine protease that serves as a key mediator in complement system activation. MASP-2 initiates the lectin pathway by forming complexes with pattern recognition molecules such as mannose-binding lectin (MBL) and ficolins. Upon pathogen recognition by MBL, MASP-2 is activated and subsequently cleaves complement components C4 and C2, leading to the generation of C3 convertase and triggering downstream complement activation. Beyond its role in the complement cascade, MASP-2 also contributes to the coagulation pathway by cleaving prothrombin to generate thrombin, thereby linking innate immunity and hemostasis ^[5]. Emerging evidence highlights the clinical significance of MASP2 gene polymorphisms, which are associated with altered susceptibility to infectious diseases and immune-related disorders. Reduced plasma levels of MASP-2 have been linked to increased vulnerability to HIV infection, while elevated MASP-2 activity may exacerbate inflammatory responses ^[6]. Given its pivotal role in immune regulation, MASP-2 has emerged as a promising therapeutic target. Inhibition of MASP-2 is currently under investigation as a potential strategy for treating a range of conditions, including IgA nephropathy (IgAN) ^[7], atypical hemolytic uremic syndrome (aHUS), and transplant-associated thrombotic microangiopathy (TA-TMA) ^[8].

The B6-huCFB/hMASP2 mouse is a dual-gene humanized model obtained by mating B6-huCFB mice (catalog number: C001710) with B6-hMASP2 mice (catalog number: C001592). This model can be used for research on the pathological mechanisms and treatment methods of autoimmune diseases and infectious diseases, as well as the development of CFB/MASP2-targeted drugs.