Properdin, Human, mAb 3A3E1

Monoclonal antibody HM2355 (3A3E1) targets human properdin, also known as complement factor P. Properdin plays a crucial role in the complement system, which defends the body against pathogens and helps clear apoptotic and damaged cells. As a positive regulator, properdin drives the alternative pathway of complement, ensuring a robust immune response.

Properdin, a 53kDa single-chain glycoprotein, consists of six TSR (thrombospondin repeat) sequences. In blood, it primarily forms head-to-tail trimers, along with some dimers and tetramers. Leukocytes, including activated neutrophils, monocytes, T-lymphocytes, and stressed endothelial cells, produce properdin.

Properdin initiates and regulates the alternative pathway by binding to C3b and stabilizing the C3bBb convertase complex on immune complexes or foreign surfaces. This stabilization enhances the pathway by promoting C3bBb-convertase formation, outcompeting C3b catabolism by factor I (with factor H as a cofactor). This process generates the alternative pathway C5 convertase (C3bBb3b), triggering the terminal pathway of complement activation. The alternative pathway can drive up to 80% of terminal pathway activity. Additionally, properdin directly limits factor H activity, further boosting complement activation.

Recent studies show that properdin also acts as a pattern-recognition receptor (PRR), binding directly to microbial surfaces, apoptotic, and necrotic cells. This ability to recognize “dangerous non-self” and “altered self” underscores properdin’s key role in immune regulation. Dysregulated properdin activity in the alternative pathway contributes to autoimmune diseases such as asthma, arthritis, septic shock, age-related macular degeneration (AMD), and C3 glomerulopathy. These findings position properdin as a promising therapeutic target in various conditions.

Antibody 3A3E1 works effectively in ELISA, western blotting (non-reduced conditions only), and functional assays that inhibit the alternative pathway of complement, such as our Alternative Complement Assay (HK3012).