T cells in cryptopatch aggregates share TCR gamma variable region junctional sequences with gamma delta T cells in the small intestinal epithelium of mice
Podd, B.S.; Thoits, J.; Whitley, N.; Cheng, H-Yuan.; Kudla, K.L.; Taniguchi, H.; Halkias, J.; Goth, K.; Camerini, V.
Journal of Immunology 176(11): 6532-6542
2006
ISSN/ISBN: 0022-1767 PMID: 16709810 Document Number: 598342
The role of cryptopatch aggregates in the development of intestinal intraepithelial lymphocytes (IEL) is a matter of controversy. Therefore, an important question is whether T cells in cryptopatch aggregates are lineally related to IEL. We hypothesized that if gamma delta(+) IEL derive from T cells in cryptopatch aggregates, then a clonal relationship would exist between the two populations. To test this hypothesis, we compared the sequence of rearranged TCR gamma variable region 5 genes in gamma delta(+) IEL and cryptopatch cells. We purified IEL by FACS and cryptopatch cells were isolated from frozen sections of the intestine by laser-assisted microdissection. PCR showed that TCR gamma variable region 5 was rearranged in gamma delta(+) IEL and in CD3(+) cryptopatch cells, but not in CD3(-) cryptopatch cells. DNA sequence analysis showed that the frequency of in-frame junctions in cryptopatch aggregates was at a level consistent with positive selection in both wild-type and athymic nude mice. In addition, the predicted amino acid sequences of V-J junctions present in gamma delta(+) IEL and cryptopatch cells were encoded by identical nucleotide sequences. By contrast, the frequency of in-frame joints was significantly reduced in cryptopatch cells isolated from TCR 5-deficient mice, indicating that the enrichment of in-frame joints in cryptopatch cells must normally depend on expression of surface gamma delta TCR. Our results are consistent with the hypothesis that a subset of gamma delta(+) IEL are related to T cells in cryptopatch aggregates. The precise role of cryptopatch aggregates in intestinal gamma delta(+) T cell homeostasis still needs to be determined.