Age‐related changes in T cell subsets were examined in intestinal intraepithelial lymphocytes (i‐IEL), which contain unique T cells differentiating extrathymically. In 2‐month‐old mice bred under conventional condition, i‐IEL consisted of a large number of CD4−CD8α/α+ cells bearing either T cell receptor (TcR)α/β or TcRγ/δ and only a few CD4+CD8α− cells. In aged mice (6 months old and 24 months old), unique CD4+CD8α/α+ i‐IEL bearing TcRα/β increased in number and conversely the proportion of TcRγ/δ+ i‐IEL was decreased. Such an increase in number of CD4+CD8α/α+ cells was detected in i‐IEL from aged (14‐months old) nude mice, but not in aged (14 months old) germ‐free mice, suggesting that a significant fraction of TcRα/β T cells such as CD4+CD8α+ i‐IEL can develop along an extrathymic pathway under the influence of intestinal microflora with age.
All Science Journal Classification (ASJC) codes
- Immunology and Allergy