Alec Redwood wrote:
>> A question.
>> T-cells are oftern seen in atherosclerotic lesions, they are also seen,
> to a lesser degree, in a process known as neo-intimal hyperplasia, which
> is seen in patients following vein grafts. There is some discussion
> that T-cells in atherosclerotic lesions are seeing some pathogen
> (although this is very debatable). However to the best of my knowledge
> there is no such evidence in neo-intimal hyperplasia (basically a
> thickening of the blood vessel wall as a result of smooth muscle
> proliferation). Certain models in nude and immunosuppressed (t-cell
> depleted or cylco A) rats show that T-cells can either increase or
> degrease neo-intimal hyperplasia.
>> The question...more of a discussion actually
>> What are they doing there? There is no evidence of an Ag (could it be
> self). If they are just by standers why do they have an effect? What
> activates them to produce IFN-gamma (as some suggest)... no Ag (and
> probably no second signal). This seems to be a forgoten area as many
> "healing" responses appear to have a T-cell component. Why are they
> there and how do they function...aparently outside their normal Ag
> sepecific role...In fact do they function in this role, is it all
> artifact.
>> Any suggestions?
The first question that comes to my mind is, are the T cells
participating in an antigen-specific response?
Are there any mouse models of atherosclerotic lesions (AL) and/or
neointimal hyperplasia (NIHP) wherein T cells are found as you
described? If experiments could be done in mice, then TCR transgenic
mice on a RAG -/- background might be useful (i.e., all T cells
expressing a single identical antigen-specific T cell receptor). First,
one could ask if T cells are present in AL or NIHP in these trangenic
mice when the conditions are induced. If T cells from several TCR t.g.
mice can be shown to participate, that could be evidence in favor of a
role for T cells REGARDLESS of their antigen specificity.
Besides looking in the trangenic mice themselves, adoptive transfer
experiments could be employed, utilizing a dye to track the t.g. T cells
(such as CFSE, Molecular Probes) or an idiotypic antibody specific for
the t.g. TCR. One possible result (of the many possibilities) might be
that wild-type T cells isolated from the lesions actually home back to
such lesions in adoptive transfers, but T cells of a single known
specificity never do (indicating a requirement for antigen specificity).
Do you know if the T cells involved express the alpha-beta, or
gamma-delta TCR? Gamma-delta T cells are possibly less
antigen-restricted in their responses than the classical alpha-beta T
cells.
--Adam Schrum
University of Pennsylvania
