Characterization of CD4(+)CD8 alpha alpha(+) and CD4(-)CD8 alpha alpha(+) intestinal intraepithelial lymphocytes in rats

Intestinal intraepithelial lymphocytes (i-IEL) of aged rats comprise CD4(+) CD8 alpha alpha(+) and CD4(-)CD8 alpha alpha(+) T cells expressing TCR alph a beta. In the present study, we compared characteristics between CD4(+)CD8 alpha alpha(+) and CD4(-)CD8 alpha alpha(+) i-IEL, which were purified by a cell sorter from the i-IEL of 6-month-old Lewis rats. Most of the CD4(+)C D8 alpha alpha(+) i-IEL were of the CD44(high) phenotype, while CD4(-)CD8 a lpha alpha(+) i-IEL were CD44(low). V-beta usage in the CD4(-)CD8 alpha alp ha(+) i-IEL was much diversified, while CD4(+)CD8 alpha alpha(+) i-IEL show ed a skewed V-beta repertoire. The CD4(+)CD8 alpha alpha(+) i-IEL but not t he CD4(-)CD8 alpha alpha(+) i-IEL proliferated in response to syngeneic spl een cells, which was partially inhibited by addition of anti-MHC class I mA b, The CD4(+)CD8 alpha alpha(+) i-IEL produced IFN-gamma and IL-2 but no IL -4 or transforming growth factor (TGF)-beta in response to syngeneic spleen cells, while CD4(-)CD8 alpha alpha(+) i-IEL produced abundant levels of TG F-beta but no IL-2, IFN-gamma or IL-4. CD4(+)CD8 alpha alpha(+) i-IEL proli ferated in response to exogenous IL-2 but not to IL-15, while CD4(-)CD8 alp ha alpha(+) i-IEL could respond to IL-15 as well as IL-2. These results sug gest that a significant fraction of CD4(+)CD8 alpha alpha(+) i-IEL belongs to T(h)1-type T cells capable of responding to self-MHC class I, while CD4( -)CD8 alpha alpha(+) i-IEL are a unique population with a diversified V-bet a repertoire that respond to IL-15 in rats.