| Summary: | 碩士 === 中國文化大學 === 生物科技研究所 === 85 === Intestinal intraepithelial lymphocytes (IEL) are located
above the basement membrane and between the epithelial cells
covering the intestine lumen. They are likely the first group of
immune cells that encounter antigens and pathogens passing
through the intestine. IEL are phenotypically and functionally
distinct from other peripheral T cells. The majority of IEL, e.
g. about 70 % in C57BL/6 (B6) mice, are CD8+ T cells.
Approximately half of IEL express alpha beta-T cell receptor
(TCRalpha beta) which can be divided into two subpopulations
based on CD8 alpha beta+ or CD8 alpha alpha+ expression.
Another half of IEL express gamma delta -TCR and are composed
of CD8 alpha alpha+ and CD4-CD8- subsets. It hasbeen shown that
all IEL develop extrathymically. IEL are also different from
other peripheral T cells in regard to their activation
requirement and responses to in vitro stimuli. Reversible
protein phosphorylation ontyrosine residues has been shown to
play an essential role in signal transduction pathways, which
regulate T cell growth and differentiation. The opposing dynamic
activities of protein tyrosine kinases (PTKs) and protein
tyrosine phosphatases (PTPs) control protein phosphorylation.
All PTPs contain highly conserved catalytic domain, which can be
amplified by degenerate primers. To elucidate the role that PTPs
may play in IEL development and activation, PTPs expressed in
CD8 alpha beta+ TCR alpha beta+ IEL or CD8+ lymph node (LN)
cells after stimulated with plate-bound anti-TCR beta monoclonal
antibody (mAb), and anti-CD28 mAb and exogenous interleukine-2
(IL-2) were investigated by a PCR-based cloning method.
Sequencing of 178 PTP specific cDNA subclones generated from CD8
alpha beta+ TCR alpha beta+ IEL identified 9 species of PTPs,
including CD45, PTP kappa, PTP1B, HCP (PTP1C), PTP2 (MPTP),
PTPase MEG2, PTP-RL10, the murine homologue of human PTPeta, and
HPTP alpha. On the other hand, sequencing of 156 PTP specific
cDNA subclones generated from CD8+ LN cells identified 8
different PTPs species, including CD45, PTPT9, STEP61, PTP1B,
HCP (PTP1C), PTP2 (MPTP), PTPase MEG2, and the murine homologue
of human PTP alpha. The differences in PTPs profiles between CD8
alpha beta+ TCR alpha beta+ IEL and CD8+ LN cells suggest that
PTP may be one of the causes of the unique properties of IEL.
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