Preservation of functioning human thyroid organoids in the scid mouse: II. Biased use of intrathyroidal T cell receptor V genes [see comments]

The severe combined immunodeficiency (scid) mouse, which lacks functional B cells and T cells, has proven a useful model for exploring the survival of transplanted human lymphocytes and thyrocytes. In order to further characterize T cell infiltrates in reconstituted sc human thyroid organoids, we examined for the presence of 18 human T cell receptor (hTcR) V alpha and 21 hTcR V beta gene families using polymerase chain reaction (PCR) analysis. Human TcR V gene activity was confirmed by Southern blot analysis of the PCR fragments from all but one of the thyroid organoids, confirming the continued survival of human T cells within the thyroid organoids. However, only 3.5 out of 18 V alpha and 5.9 out of 21 V beta gene families were detected in these human thyroid organoids indicating a marked bias in T cell survival. Sequencing of the V-D-J regions of the amplified TcR fragments showed that approximately 60% of the sequences were representative of clonally expanded T cells. Hence, these passenger T cells exhibited highly biased use of particular TcR V gene families similar to that observed previously in thyroid tissue and intrathyroidal T cell cultures. Furthermore, variations in the V-D-J regions of sequences from similar V gene families indicated that the V gene region was important in T cell selection rather than the CD3 region