When does gut flora become pathogenic?

Andrew S. Louka alouka at writeme.com
Tue Jun 23 07:31:42 EST 1998


There are ten times as many bacteria as there are cells in each of us. 
Many are of course, in the gut --commonly referred to as the "normal gut
flora".  Ninety percent of T lymphocytes are also found along the GI
tract.

If faeces (containing normal host flora) are homogenized then injectred
under the skin of the donor, a commonly fatal inflammatory response is
induced.  One could envisage a situation where anergy (absence of
co-stimulation leading to a refactory period where stimulation cannot be
achieved) is a significant factor in the gut where the normal flora
reside, and that co-stimulation (presumed to be necessary (*)) leads to
the "effective" immune response in the skin.

Is there any evidence to support this theory?  I hesitate to accept it,
partly because you only need relocate the flora bacteria by a few
centimetres before an acute response is seen (naturally, there is a
constant low level of inflammation along the length of the gut).  My
second cause for hesitation is that it is, as far as I am aware,
impossible to study anergic cells:  how do you isolate them?!

Any thoughts?

Andrew Louka

* I am aware of a recently published article which casts new light on our
understanding of co-stimulation in CD8+ T cells, but haven't read it yet. 
Pardigon N, Bercovici N, Calbo S et al.  Role of co-stimulation in CD8+ T
cell activation.  International Immunology. 10(5);619-30
Institute of Transplantation Immunology
Rikshospitalet University of Oslo
N-0027 OSLO,
Norway



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