Prenatal development of the intestinal and extraintestinal T cell receptor δ repertoire: Identical, dominant TCRDV3 transcripts are present in different fetal piglets

Abstract

//B T cells are likely to play an important role in autoimmune conditions such as Crohns disease and ulcerative colitis. However the functions and the antigens recognized by ~/B T cells are largely unknown. It is thought that they recognize antigens expressed by damaged or stressed epithelial cells. In order to establish a large animal model for analyzing the effects of age and microbial factors we have previously characterized the porcine r TCR repertoire in multiple intestinal and extraintestinal sites. We could demonstrate that the TCR B repertoire is highly compartmentalized not only within differetu organs but also within the intestinal tract. In the present study we analyzed the prenatal development of the porcine TCR 8 repertoire to gain further insight into the nature and development of these cells. Methods: Fetal ttssues from the jejunum, colon, spleen, thymus, liver, bone marrow and PBMC were obtained from fetal piglets between 38 and 114 days of gestation. TCRDV1-DV5 transcripts were amplified by RT-PCR after which complementarity-determining region (CDR) 3 spectratyping was performed. Individual bands were excised from the gels, cloned and sequenced. Results: 1) At 38 days gestation (DG) hardly any TCR 5 transcripts could be detected and only TCRDV1 and DV3 transcripts could be amplified from the thynuc samples. Thus, the ~//B TCR is rarely expressed at this early age. 2) At DG57 TCRDVI-DV5 transcripts could be amplified from all organs and spectratyping showed a significant increase in the CRD3 length during fetal life. 3) In comrast to the other DV families, the TCRDV3 repertoire was highly oligoclonal at DG57 and a dominant band of identical CDR3 length was present in all organs. This dominant band was still present, although less dominant, in the older piglets. 4) Sequence analysis of these dominant bands revealed one identical TCRDV3 transcript which lacked N region diversity. 5) This TCRDV3 transcript was infrequently found during the first weeks after birth but never in adult pigs. Conclusions: The porcine TCR 8 repertoire diversifies during gestation and is polyclonal at birth The dominam TCRDV3 transcript, which is present in all fetus at mid gestation, indicates an important function of this particular ,//'6 T cell subset during gestation. The increase of CDR3 length during fetal life indicates increasing TdT activity. In contrast to adult pigs there is no compartmentalization of the TCR 5 repertoire between different organs.