The Fab, also known as the antigen-binding fragment, is the region within the antibody structure capable of binding antigens. It consists of an entire light chain (comprising both the variable and constant regions) and part of the heavy chain structure (specifically the variable region and one constant region domain). The light chain and heavy chain are connected via a disulfide bond. Fab fragments are relatively small, with a molecular weight of approximately 47-48 kDa. They are typically prepared using Phage Display Technology or mammalian cell expression systems. In cancer therapy, Fab fragments can be utilized for targeting specific tumor antigens. They also serve as probes for detecting specific molecular markers. Consequently, they find widespread application in disease diagnosis and treatment, as well as biological research. Compared to full-length IgG antibodies, Fab antibodies exhibit greater tissue penetration and lower immunogenicity.

KMD Bioscience combines mature Recombinant Antibody Expression Service with Phage Display Technology to prepare antibodies for clients, which are widely used in research, diagnostics, and therapeutics. Recombinant antibody expression is a critical step in antibody drug development. Continuous optimization and improvement of expression technologies enhance antibody quality and yield, supporting the clinical application and industrial development of antibody drugs. Protein expression systems are categorized based on the host cell type, primarily prokaryotic and eukaryotic systems. The prokaryotic expression system mainly utilizes E. coli as the host cell, offering advantages like simplicity of operation and low cost. We employ prokaryotic expression systems to produce large quantities of Fab antibodies within a short turnaround time. Furthermore, our experimental researchers optimize conditions such as induction time, temperature, and reagents to ensure soluble expression of Fab antibodies with retained antibody activity. We possess eukaryotic cell lines, including mammalian, yeast, and insect cells, enabling the expression of Fab antibodies with post-translational modifications. We implement appropriate modifications and optimizations to the expression vectors to enhance both the expression level and purification efficiency of Fab antibodies.

The Mammalian Expression System typically employs transient or stable expression approaches. It better mimics natural protein expression and modification processes while possessing efficient transcriptional and translational capabilities. Consequently, this system enables high-yield production of target proteins. KMD Bioscience utilizes Mammalian Expression Systems such as HEK293 or CHO cell lines. Through optimization of culture media, expression vectors, and transfection conditions, we produce Fab antibodies in large quantities for applications in Drug Development and Biologics. We perform quality control and functional validation on expressed Fab antibodies. This ensures the antibodies possess both affinity and specificity.