|
Recent studies have suggested that intestinal intraepithelial
lymphocytes (iIEL) iIELs are quite different from peripheral T
cells in various aspects of their development and functions. By
characterizing iIEL subpopulations according to their surface
expression of CD4, CD8a, and CD8b chains, we analyzed ab T cell
receptor (TCR) Vb chain usage by flow cytometry, and found
that, unlike in human iIEL, there is no preferential usage of
Vb in murine iIEL. Within the aaCD8 abTCR subpopulation, Vb6+
cells was remained in Mls-1a mice. Similar frequency of Vb14+
CD8+ iIEL was found in Kk mice as in Kb mice. It suggests that
selection of abTCR in aaCD8 iIEL during their maturation is
different from that of peripheral T cells. Analysis of CD44
and Ly6C expression revealed that not only aaCD8 but abCD8 and
CD4 iIEL expressed differently from that of peripheral CD4 and
CD8 cells. We further characterize iIEL subpopulations by
examining their proliferation activity and cytokine production
in response to stimulation via abTCR with or without
costimulation of CD28 or CD2. We found that CD4 and abCD8 iIEL
proliferate in the presence of exogenous IL2, whereas aaCD8
iIEL showed no proliferative response. The same response
pattern was observed for IL2 and IFN-r production after
stimulation, even under the condition without exogenous IL2 and
no detectable proliferation response. None of the iIEL
subpopulations nor lymph node CD8 cells produce IL4 in response
to the above stimuli. The present study shows that CD4, abCD8,
and aaCD8 iIEL are quite distinct from peripheral T cells in
surface marker and functions. Different iIEL subsets may have
different function. However, how the unique properties of iIEL
relate to their functions in vivo requires further
investigation.
|