QUANTITATIVE-ANALYSIS OF PEPTIDES FROM MYELIN BASIC-PROTEIN BINDING TO THE MHC CLASS-II PROTEIN, I-A(U), WHICH CONFERS SUSCEPTIBILITY TO EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS
L. Fugger et al., QUANTITATIVE-ANALYSIS OF PEPTIDES FROM MYELIN BASIC-PROTEIN BINDING TO THE MHC CLASS-II PROTEIN, I-A(U), WHICH CONFERS SUSCEPTIBILITY TO EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS, Molecular medicine, 2(2), 1996, pp. 181-188
Citations number
24
Categorie Soggetti
Biology,"Medicine, Research & Experimental","Cell Biology
Background: An important issue in autoimmune diseases mediated by T ce
lls, such as experimental allergic encephalomyelitis (EAE), is the aff
inity of the disease inducing determinants for MHC class II proteins.
Tolerance, either due to clonal deletion or anergy induction, is thoug
ht to require high-affinity interactions between peptides and MHC mole
cules. Low-affinity binding is compatible with the hypothesis that bre
aking tolerance to self proteins does nor have to occur for onset of d
isease. In contrast, a high-affinity interaction implies that an event
leading to a breakdown of tolerance is central to the autoimmune proc
ess. Materials and Methods: Detergent-solubilized and af finity-purifi
ed I-A(u) was incubated with varying concentrations of a set of peptid
es from myelin basic protein and a biotinylated peptide agonist. The s
pecific complexes were separated from excess peptide by capture on ant
ibody-coated plates, and the affinity of the peptides was measured by
adding europium-labeled streptavidin and measuring the resultant fluor
escence. Results: The immunodominant and encephalitogenic determinant
Ac 1-11, was shown to bind to I-A(u) relatively poorly (IC50 = 100 mu
M), demonstrating that in this protein, immunodominance did not correl
ate with high-affinity binding. In contrast with the natural sequence.
the ability of shorter analogs to induce EAE did correlate with their
apparent affinity. Conclusions: The dominance of the natural determin
ant does nor arise from a high-affinity interaction with the MHC class
II. molecule. This suggests that other mechanisms are operative and t
hat the specific T cell for this peptide/MHC ligand is of high affinit
y.