Immunoglobulin variable regions in molecules exhibiting characteristics of innate and adaptive immune receptors

Abstract

The antigen combining sites of immunoglobulin (Ig) and T cell antigen receptors (TCRs), which are present in all jawed vertebrates, consist of a paired variable (V) domain heterodimer that exhibits varying degrees of germline- and extraordinarily high levels of somatically-derived variation. The near limitless variation in receptor specificity on the surface of individual lymphocytes is the basis for clonal selection in the adaptive immune response. A basic question arises as to whether or not there are other forms of immune-type receptors in vertebrates as well as in invertebrates that derive immune specificity through sequence differences in V domains. Our laboratory has discovered two such families of molecules, the novel immune-type receptors and the variable region-containing chitin-binding proteins. Both families of molecules encode V domains that share some characteristics of adaptive immune receptors but likely mediate innate functions.

Gut CaVP is an innate immune protein against bacterial challenge in amphioxus Branchiostoma belcheri

“…Interestingly, CaVP not only differentiated Gramnegative bacterium from Gram-positive bacterium, but also mounted different immune responses to homogeneous and heterogeneous challenge bacteria. However, this response was significantly different from the lymphocytes or an antibody-based response that vertebrates possess, which possesses epitopespecific [31,32]. Combining with our previous report on SCP specific immune priming to invading bacteria [14], we conclude that amphioxus calcium-binding proteins play an important role in …”

Tench (Tinca tinca) high-throughput transcriptomics reveal feed dependent gut profiles

“…Genes encoding cell-surface receptors characterised by the presence of a variable number of Ig domains (e.g., V-type) (Litman et al, 2007), cluster of differentiation 48 (cd48), expressed on almost all …”

On Origin and Evolution of the Antibody Molecule

“…Since lacking the basic mechanisms for somatic diversification but possessing a VJ segment continuity, such non-rearranging Ig-like genes would presumably have been served as primordial substrates that have led to the emergence of recombining antigen-binding receptors [ 38 , 39 ]. Evolutionary and comparative studies indicate that NITRs are likely to have diverged from an Ig gene cluster following a gene birth-and-death process, which accounts for their rapid diversification [ 40 ], a feature in common with Igs and killer-cell immunoglobulin-like receptors (KIRs) [ 41 ]. Apart from Igs, NITRs may represent the sole example of a receptor gene complex encoding a diversified family of V regions in vertebrates and represent a compelling case for parallel evolution of V regions of both adaptive and innate immune receptors [ 42 ].…”