Naturally occurring antibodies devoid of light chains

Abstract

RANDOM association of VL and VH repertoires contributes considerably to antibody diversity1. The diversity and the affinity are then increased by hypermutation in B cells located in germinal centres2. Except in the case of 'heavy chain' disease3, naturally occurring heavy-chain antibodies have not been described, although antigen binding has been demonstrated for separated heavy chains4 or cloned VH domains5. Here we investigate the presence of considerable amounts of IgG-like material of Mr 100K in the serum of the camel (Camelus dromedarius)6. These molecules are composed of heavy-chain dimers and are devoid of light chains, but nevertheless have an extensive antigen-binding repertoire, a finding that calls into question the role of light chains in the camel. Camel heavy-chain IgGs lack CH1, which in one IgG class might be structurally replaced by an extended hinge. Heavy-chain IgGs are a feature of all camelids. These findings open new perspectives in the engineering of antibodies.