Isotype controls are a type of primary antibodies that lack specificity to the target, but match the class and type of the primary antibody used in in vitro and in vivo studies. Isotype controls are often used to measure the level of non-specific background signal caused by binding non-specifically to Fc receptors on the cell surface, or other cellular molecules.
Most antibodies consist of four components: two heavy chains and two light chains. This complexity makes their engineering challenging and recombinant expression difficult. Interestingly, camelids and sharks produce antibodies that are only composed of heavy chains (heavy chain antibodies, hcAbs). Although the hcAbs of camelids and sharks differ somewhat in structure, their single N-terminal domain (VHH and VNAR, respectively) contain the ability to bind an antigen without domain pairing using three complementarity-determining regions (CDRs). These N-terminal domains have been named single domain antibodies (sdAbs) or nanobodies and have become promising tools for life scientists, protein engineers and synthetic biologists alike.
