The immune system is composed of two subsystems—the innate immune system and the
adaptive immune system. The innate immune system is the first to respond to pathogens and …

The adaptive immune system arose 500 million years ago in ectothermic (cold-blooded)
vertebrates. Classically, the adaptive immune system has been defined by the presence of …

The B cell receptor and secreted antibody are at the nexus of humoral adaptive immunity. In
this review, we summarize what is known of the immunoglobulin genes of jawed …

The only immunoglobulin heavy-chain classes known so far in teleosts have been μ and δ.
We identify here a previously unknown class, immunoglobulin ζ, expressed in zebrafish and …

The study of immunoglobulin genes in non-mouse and non-human models has shown that
different vertebrate groups have evolved distinct methods of generating antibody diversity …

Highlights•Camelids and sharks comprise heavy chain-only antibodies devoid of light
chains.•Their variable domains are able to address cryptic and recessed epitopes.•These …

Approximately 500 million years ago, two types of recombinatorial adaptive immune systems
(AISs) arose in vertebrates. The jawed vertebrates diversify their repertoire of …

This review discusses evolution of the process of Ig heavy chain class switching, relating it to
the first appearance of somatic hypermutation (SHM) of variable region genes. First, we …

In addition to antibodies with the classical composition of heavy and light chains, the
adaptive immune repertoire of sharks also includes a heavy-chain only isotype, where …

There are 3 H chain and 3 L chain isotypes in the cartilaginous fish, all encoded by genes in
the so-called cluster (VDDJ, VJ) organization. The H chain isotypes IgM and IgNAR, are …