Emory University School of Medicine, USA
Sabyasachi Das has completed his Ph.D. from Jadavpur University, India and postdoctoral studies from Pennsylvania State University, USA. His current research interest is the evolution of adaptive immune system and immunity. He has published more than 25 papers in reputed journals and serving as an editorial board member of repute.
The requirement of self-defense in the ongoing struggle for survival led to the evolution of complex immune systems. About 500 million years ago two types of adaptive immune systems (AIS) arose in vertebrates which featured migratory populations of lymphocytes that express a diverse repertoire of recognition receptors. Jawed vertebrates somatically diversify the repertoire of immunoglobulin-domain based B and T cell antigen receptors through the rearrangement of V(D)J gene segments and somatic hypermutation, whereas an alternative AIS of jawless vartibrates (lamprey and hagfish) is based on variable lymphocyte receptors (VLRs) which diversify through recombinatorial usage of leucine-rich repeat (LRR) cassettes in VLR assembly. Three VLR genes have been identified; the VLRB gene is expressed by B-like lymphocytes, while VLRA and VLRC are expressed by two different lineages of T-like cells which in some ways resemble thymus-derived T cells lymphocytes of jawed vertebrates. Analysis of the genomic organization of VLRA/VLRC has revealed shared usage of genomic donor cassettes during VLRA and VLRC assembly somewhat analogous to the shared usage of variable gene segments during TCRA/TCRD locus rearrangement in jawed vertebrates. The recent availability of the lamprey genome sequence may contribute to the reconstruction of VLR phylogeny and insight into how the adaptive immune function evolved in the context of well developed innate immunity.