Paul J Travers (p_travers at icrf.icnet.uk) wrote:
: In article <3r8gob$mdl at jhunix1.hcf.jhu.edu>, ejf at welchlink.uoregon.edu: (Ephraim Fuchs) wrote:
: Ephraim,
: I suspect your statement is a little too general. How do you
: account for the observation that inherited deficiencies in late (ie lytic
: pathway) complement components are specifically associated with
: susceptibility to Neisseria infections (a gram- organism). In these cases
: the early complement components are intact and capable of acting as
: opsonins, but this is insufficient to control this particular group of
: pathogens.
: As to whether in general adaptive immune responses are associated
: with resistance to gram- bacteria, isn't there a window of susceptibilty
: in infants whose onset correlates with the disappearance of maternal
: immunoglobulin and which decays as the infants own immunoglobulin levels
: rise? Does this not suggest that antibody (which I would class as part of
: the adaptive immune system) plays a role in host defence against gram-
: pathogens?
Paul,
You are absolutely correct in that I am being too general in my
statement. There are gram - bacteria against which antibodies, but not T
cells, play a useful role-for instance, Pneumococcus, Hemophilus
Influenzae, and Neisseria spp. If I remember correctly (and it has been
a very long time since I have had any instruction in infectious
diseases), this is because these organisms are encapsulated and contain
antigenic polysaccharides (which of course cannot be recognized by T
cells) in their capsules. But consider your "typical" gram negative
organism, like E. coli, Pseudomonas, Enterobacter, Serratia, etc.
Against these organisms I would propose that the adaptive immune system
plays no role, and an individual that has survived an infection with one
of these organisms has no better chance of surviving a reinfection than
the first time around. This is why I believe that the induction of
"costimulatory" molecules by LPS of gram negative bacteria cannot be very
useful.
By the way, didn't you write a textbook with Charlie Janeway? Should I
buy it?
Ephraim Fuchs
ejf at welchlink.welch.jhu.edu
