T cell recognition of foreign peptide antigen and toler-ance to self peptides is key to the proper function of the immune system.Usually,in the thymus T cells that rec-ognize self MHC+self peptides are deleted and tho...T cell recognition of foreign peptide antigen and toler-ance to self peptides is key to the proper function of the immune system.Usually,in the thymus T cells that rec-ognize self MHC+self peptides are deleted and those with the potential to recognize self MHC+foreign pep-tides are selected to mature.However there are excep-tions to these rules.Autoimmunity and allergy are two of the most common immune diseases that can be related to recognition of self.Many genes work together to lead to autoimmunity.Of those,particular MHC alleles are the most strongly associated,reflecting the key importance of MHC presentation of self peptides in autoimmunity.T cells specific for combinations of self MHC and self pep-tides may escape thymus deletion,and thus be able to drive autoimmunity,for several reasons:the relevant self peptide may be presented at low abundance in the thy-mus but at high level in particular peripheral tissues;the relevant self peptide may bind to MHC in an unusual register,not present in the thymus but apparent else-where;finally the relevant self peptide may be post translationally modified in a tissue specific fashion.In some types of allergy,the peptide+MHC combination may also be fully derived from self.However the combi-nation in question may be modified by the presence of other ligands,such as small drug molecules or metal ions.Thus these types of allergies may act like the post translationally modified peptides involved some types of autoimmunity.展开更多
文摘T cell recognition of foreign peptide antigen and toler-ance to self peptides is key to the proper function of the immune system.Usually,in the thymus T cells that rec-ognize self MHC+self peptides are deleted and those with the potential to recognize self MHC+foreign pep-tides are selected to mature.However there are excep-tions to these rules.Autoimmunity and allergy are two of the most common immune diseases that can be related to recognition of self.Many genes work together to lead to autoimmunity.Of those,particular MHC alleles are the most strongly associated,reflecting the key importance of MHC presentation of self peptides in autoimmunity.T cells specific for combinations of self MHC and self pep-tides may escape thymus deletion,and thus be able to drive autoimmunity,for several reasons:the relevant self peptide may be presented at low abundance in the thy-mus but at high level in particular peripheral tissues;the relevant self peptide may bind to MHC in an unusual register,not present in the thymus but apparent else-where;finally the relevant self peptide may be post translationally modified in a tissue specific fashion.In some types of allergy,the peptide+MHC combination may also be fully derived from self.However the combi-nation in question may be modified by the presence of other ligands,such as small drug molecules or metal ions.Thus these types of allergies may act like the post translationally modified peptides involved some types of autoimmunity.
