Recognition of self vs non-self by macrophages?

Ian A. York york at mbcrr.dfci.harvard.edu
Fri Nov 4 15:29:20 EST 1994


In article <199411041533.HAA01434 at net.bio.net> kdelgert at vt.edu (Klaus D. Elgert) writes:
>        A question arose in our graduate level immunology course.  "How do 
>macrophages distinguish between self and non-self?"  Macrophages are 

I think there are two halves of your question: (1) How do macrophages 
endocytose foreign rather than self antigen and (2) how do they present 
foriegn material rather than self after endocytosis.  The short answer 
is, they do not differentiate.  This is true particularly at the level of 
presentation: self and foreign antigens are presented more or less at 
random (i.e. if an antigen has the appropriate motifs and the other 
caveats are met - cleavage, etc - then that epitope will be presented on 
MHC molecules.  The discrimination here is at the level of the TcR; 
although self-antigen is presented by macrophages, the T cells simply do 
not recognize it.  (Well, it isn't "simple," I guess.)  
	As far as endocytosis is concerned, there is not very precise 
differentiation here between self and non-self antigens.  There is some, 
however.  As well as the opsinizing effects of antibody and complement, 
there seems to be some recognition of different lipids.  I can't recall 
the whole story on this, but for example during apoptosis there appears 
to be alterations of the cell membrane, with a loss of the normal 
assymetry of the membrane; the normally hidden lipids act as opsinins and 
enhance phagocytosis.  This probably is part of the red cell situation 
you mentioned.  I believe there may be other opsinins which are exposed 
or prodced during apoptosis and probably other physiological states.  

Hope this helps.

Ian
-- 
Ian York   (york at mbcrr.harvard.edu)
Dana-Farber Cancer Institute, 44 Binney St., Boston MA 02115
Phone (617)-632-4328     Fax  (617)-632-2627




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