Activated alpha beta -CD8 super(+), but not alpha alpha -CD8 super(+), TCR- alpha beta super(+) murine intestinal intraepithelial lymphocytes can mediate perforin-based cytotoxicity, whereas both subsets are active in Fas-based cytotoxicity

CD8 single-positive (CD8 super(+)) T cells in murine intestinal intraepithelial lymphocytes (ilEL) consist of alpha alpha -CD8 super(+) and alpha beta -CD8 super(+) subpopulations. Cytotoxicity represents an important function of peripheral CD8 super(+) T cells, so we examined perforin-granzyme-based and Fas-based cytotoxicity of activated CD8 super(+) TCR- alpha beta super(+) ilEL subsets. We found that allospecific CTL activity was induced from alpha beta -CD8 super(+) ilEL but not from alpha alpha -CD8 super(+) iLEL even when allospecific TCR were present on the ilEL, as demonstrated by using 2C TCR transgenic mice. On the other hand, both CD8 super(+) ilEL subsets proliferated upon allostimulation with a lower responder frequency than CD8 super(+) LN cells. The alpha alpha -CD8 super(+) TCR- alpha beta super(+) ilEL appeared to lose their ability to perform perforin-based killing after activation through TCR because fresh cells lysed P815 cells coated with anti-TCR beta -chain (TCR- beta ) mAb, whereas cells activated by plate-bound anti-TCR mAb did not. Of interest, both activated CD8 super(+) TCR- alpha beta super(+) ilEL subsets, but not fresh cells, were able to mediate Fas-based killing when triggered with PMA and Ca super(2+) ionophore.