Proliferating intestinal gamma/delta T cells recirculate rapidly and are a major source of the gamma/delta T cell pool in the peripheral blood.

The proliferation, recirculation and repertoire of gut-derived gamma/delta T cells were studied in pigs in vivo. Proliferating gamma/delta T cells (detected by BrdU labeling) are present in all intestinal compartments. In the gut lymph approximately 0.5% of all gamma/delta T cells were proliferating. These gut-derived BrdU(+) gamma/delta T cells re-enter the intestinal tissues, and re-appear in the intestinal lymph far more often than other cells: about 22% of i.v.-injected BrdU(+) gamma/delta T cells were recovered again from the intestinal lymph within 72 h (compare with BrdU(+) B cells 2%, and other BrdU(+) T cells 10%). The contribution of the gut to the migrating gamma/delta T cell pool in the blood became obvious: the proportion of BrdU(+) gamma/delta T cells was three-times larger in control versus cannulated pigs. In 9-month-old pigs, clonally expanded T cells were identified in the intestine by complementarity-determining region 3 spectratyping of TCR-delta transcripts. Such expansions were not visible in the blood or intestinal lymph. The distribution of gamma/delta T cells within the intestinal tract is likely to depend to a large degree on the proliferation and the migratory properties of these cells which are different to those of alpha/beta T cells and B lymphocytes.