Effect of neonatal thymectomy on murine small intestinal intraepithelial lymphocytes expressing T cell receptor alpha beta and "clonally forbidden V beta s".

Neonatal thymectomy NTX performed on Day 3 of C3H mice causes over a 50% reduction in small intestinal intraepithelial lymphocytes (IEL) expressing the alpha beta T cell receptor (TCR) when analyzed at 10 weeks of age. Furthermore, this reduction is most notable in alpha beta TCR IEL expressing the CD8 alpha homodimer and no Thy 1 marker. This is in direct contradiction to the present theory that alpha beta TCR IEL expressing these markers are thymic independent. Evaluation of V beta expression shows a relative increase in V beta s which are clonally forbidden (V beta s 3, 5, 11), and which is consistent with the extrathymic origin of these particular IEL.