A kaleidoscope of hosts: Expression systems of recombinant antibody reagents for immunological assays

Monoclonal antibodies (mAbs) have been shown to be highly promising reagents used in immunological analysis of various diseases and other chronic conditions due to their specific targeting, potency, and stability. Advances in protein engineering and immunology have led to the development of recombinant monoclonal antibodies at a staggering pace. Full-length antibodies IgG are generally the preferred format, but the development of smaller formats like Fab, scFv, and sdAbs opened the floodgates for more variation. This allowed for a more flexible application of mAbs in immunological assays. A diverse set of expression systems have been used to express recombinant mAbs which includes bacterial, yeast, insect, mammalian cells, plant, cell-free and Leishmania each with distinct advantages and disadvantages. This review highlights that the selection of an optimal expression system and antibody format must be guided by the intended application, balancing yield, structural integrity, and cost. While no single host fulfils all criteria, continued advances in host engineering, synthetic design, and AI-driven optimization are expected to streamline recombinant antibody production and expand its applicability across therapeutic and diagnostic fields.