Gut tissue-resident memory T cells in coeliac disease.

This mini-review describes observations of the 1990ies with culturing of gluten-specific and astrovirus-specific CD4+ T cells from duodenal biopsies from subjects who presumably had a long time between the exposure to gluten or astrovirus antigens and the sampling of the biopsy. In these studies, it was also observed that antigen-specific CD4+ T cells migrated out of the gut biopsies during overnight culture. The findings are suggestive of memory T cells in tissue which are resident, but which also can be mobilised on antigen stimulation. Of note, these findings were made years before the term tissue-resident memory T cells was invoked. Since that time, many observations have accumulated on these gut T cells, particularly the gluten-specific T cells, and we have insight into the turnover of CD4+ T cells in the gut lamina propria. These data make it evident that human antigen-specific CD4+ T cells that can be cultured from gut biopsies indeed are bone fide tissue-resident memory T cells.