Heavy-chain antibody

Heavy - chain antibodies are antibodies that consist solely of heavy chains. They differ structurally from conventional IgG antibodies, which are composed of two heavy and two light chains. Heavy - chain antibodies were found in addition to conventional antibodies in nature previously only within the class of cartilaginous fish and in the camel family.

Structure

IgNAR of cartilaginous fish

Heavy chain antibody of the cartilaginous fish, also immunoglobulin new antigen receptor ( IgNAR ) called structurally different significantly from conventional antibodies of mammals. They consist of two heavy chains, the constant of five domains and a person responsible for antigen recognition variable domain exist. And the position of the disulfide bridges is different from the conventional antibody. Within the antigen-binding variable domains is IgNARs differ from conventional IgG antibodies by a distinct CDR3 loop.

IgG2a / ​​b and IgG3 of camels

In addition to conventional, consisting of two light and two heavy chains IgG1 antibodies, produce representatives of the camel family in addition heavy chain antibodies of the IgG2a, IgG2b and IgG3. These consist of two heavy chains which are in turn composed of two constant domains and a variable domain.

Although it is believed that the heavy chain antibodies of camels have no direct relationship to the IgNARs the Knorperlfische, show both antibody families striking similarities that are due to convergent evolution. Both IgNARs and the heavy-chain antibodies of camels have a pronounced CDR3 loop, which is involved in antigen binding and has the ability to penetrate gap structures that are inaccessible to conventional antibodies.

Use

Thanks to its simple compared to conventional antibodies structure of the variable domains find heavy chain antibodies in research and in the development of new drugs with great interest. Your consisting of only one domain with a molecular mass of only 12 to 15 kDa variable domains are the smallest antibody fragments that are still capable of antigen binding. These fragments, which are also referred to as single-domain antibodies, which combine properties of low molecular weight substances and antibodies.