General enquiry - cerebral malaria (cross posted to bionet.general)

Mark Siddall mes at zoo.toronto.edu
Sun Sep 17 01:52:05 EST 1995


In article <cranks.13.000B1519 at iafrica.com> cranks at iafrica.com (Neal Crankshaw) writes:
>A cousin of mine has just made an recovery from cerebral malaria after having 
>been brought home from Mocambique in a coma, and apparently this is quite a 
>feat. My family, who were told that they should expect the worst, are 

This IS quite a feat!!!!
Congratulations to your cousin! And thier family!!

>overjoyed, and are asking me for an explanation of the illness (being the only 
>family member with a degree in biochemistry). Well, rather than turn round and 
Okay... the deal is that malaria has a number of levels os severity...
by all accounts, cerebral malaria pretty much bites!  It is most
common, if not exclusive to P. falciparum cases of malaria.
What happens is a wierd complex set of conditions.  The parasites
infect RBCs at an enormous rate.  These RBCs start expressing
parasite antigens on their surface.  The high rate of infection causes
the patient's immmune response to up-regulate TNF (tumour necrosis
factor).  The strange thing is that TNF up-regulation, while it helps
the body's WBC's pavement to capillaries and seek out invaders, also
happens to help the RBC's expressing parasite antigens pavement to
the capillary walls too!!!  Yikes, talk about an immune system backfire!
Anyway, one of the results is that all of these infected RBCs clog up 
capillary beds.  It just so happens that capillary beds are particularly
rich in the brain, so the brain get loaded up with RBC's infected with malaria
parasites.  It's nasty looking in cross section.  
Okay, so I have over-simplified it but TNF seems to be the major player.
That is, give a monkey with cerebral malaria, antibodies to their own
TNF and you cure them of cerebral malaria (though not of malaria).
This however is impractical as a treatment as you kinda (!) need your TNF to 
be working if your immune cells are gonna be able to speak to each other

Mark
-- 
Mark E. Siddall                "I don't mind a parasite...
mes at vims.edu                    I object to a cut-rate one" 
Virginia Inst. Marine Sci.                     - Rick
Gloucester Point, VA, 23062



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