ⓘ Single-domain antibody

                                     

ⓘ Single-domain antibody

A single-domain antibody, also known as a nanobody, is an antibody fragment consisting of a single monomeric variable antibody domain. Like a whole antibody, it is able to bind selectively to a specific antigen. With a molecular weight of only 12–15 kDa, single-domain antibodies are much smaller than common antibodies which are composed of two heavy protein chains and two light chains, and even smaller than Fab fragments and single-chain variable fragments.

The first single-domain antibodies have been developed with the heavy chain antibodies found in camelids, they are referred to in h fragments. Cartilaginous fishes also have heavy chain antibodies IgNAR, immunoglobulin new antigen receptor from which single-domain antibodies are known in NAR fragments can be obtained. An alternative approach is to split the dimeric variable domains from common immunoglobulin G IgG from humans or mice into monomers. Although most of the research on single-domain antibodies is currently based on heavy chain variable domains, nanobodies derived from light chains have also been shown to bind specifically to target epitopes.

Single-domain antibodies in camelids has been shown to be as specific as regular antibodies, and in some cases they are more reliable. Also, they are easily isolated using the same procedure, phage panning, which are used for conventional antibodies which allows them to be cultured in vitro in high concentrations. The smaller size and single domain to make these antibodies it is easier to transform into bacterial cells for mass production, making them the ideal solution for research purposes.

Single-domain antibodies are being explored for various pharmaceutical applications and have potential for use in the treatment of acute coronary syndrome, cancer, and Alzheimers disease.