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Front. Immunol. | doi: 10.3389/fimmu.2018.02117

Rearranged T Cell Receptor Sequences in the Germline Genome of Channel Catfish are Preferentially Expressed in Response to Infection

  • 1Infectious Diseases, University of Georgia, United States
  • 2Pathology, University of Georgia, United States

Rearranged V(D)J genes coding for T cell receptor α and β chains are integrated into the germline genome of channel catfish. Previous analysis of expressed TCR Vβ2 repertoires demonstrated that channel catfish express multiple public clonotypes, which were shared among all the fish, following infection with a common protozoan parasite. In each case a single DNA sequence was predominately used to code for a public clonotype. We show here that the rearranged VDJ genes coding for these expressed public Vβ2 clonotypes can be amplified by PCR from germline DNA isolated from oocytes and erythrocytes. Sequencing of the Vβ2 PCR products confirmed that these expressed public Vβ2 clonotypes are integrated into the germline. Moreover, sequencing of PCR products confirmed that all five Vβ gene families and Vα1 have rearranged V(D)J genes with diverse CDR3 sequences integrated into the germline. Germline rearranged Vβ2 and Vβ4 genes retain the intron between the leader and Vβ sequence. This suggests that the germline rearranged TCR Vβ genes arose through VDJ rearrangement in T cells, and subsequently moved into the germline through DNA transposon mediated transposition. These results reveal a new dimension to the adaptive immune system of vertebrates, namely: the expression of evolutionarily conserved, rearranged V(D)J genes from the germline.

Keywords: T cell receptor, rearranged VDJ genes, germline genome, Channel catfish, immune memory

Received: 18 May 2018; Accepted: 28 Aug 2018.

Edited by:

Lars T. Hellman, Uppsala University, Sweden

Reviewed by:

Pierre Boudinot, Institut National de la Recherche Agronomique (INRA), France
Robert D. Miller, University of New Mexico, United States  

Copyright: © 2018 Findly, Niagro, Sweeney, Camus and Dickerson. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Robert C. Findly, University of Georgia, Infectious Diseases, 501 DW Brooks Drive, Athens, 30602, GA, United States, rfindly@uga.edu