Characterization of the dominant autoreactive T-cell epitope in spontaneous autoimmune haemolytic anaemia of the NZB mouse.
NZB mice spontaneously develop autoimmune haemolytic anaemia (AIHA) due to a T helper-dependent autoantibody response against the erythrocyte anion channel protein, Band 3. Here, we characterize the recognition of the Band 3 sequence 861-874, which carries the dominant, I-E(d)-restricted T cell epitope. The ability of N and C-terminal truncated versions of peptide 861-874 to elicit NZB splenic T-cell proliferation indicated that the core epitope spans residues 862-870. Next, a set of alanine substitution analogues was tested to determine which residues functioned either as MHC anchor or TCR contact residues. A combination of proliferation and MHC:peptide binding assays identified residues 862(L), 864(V), 865(L), and 869(K) as I-E(d) anchor residues, and 868(V) as the only TCR contact residue. The ability of the wild-type sequence 861-874 to compete with a high affinity reference peptide for binding to I-E(d) indicates that the escape of pathogenic NZB T cells from purging of the autoreactive repertoire cannot be attributed to ineffective presentation of peptide 861-874 by its restricting element. It will now be possible to design altered peptide ligands of Band 3 861-874, in order to further dissect the mechanisms responsible for the maintenance and loss of T cell tolerance to RBC autoantigens, and to modulate the immune response in AIHA.
Shen
Chia-Rui
CR
Department of Medicine and Therapeutics, University of Aberdeen, Aberdeen, AB25 2ZD, UK.
Ward
Frank J
FJ
Devine
Anne
A
Luross
Jeffrey A
JA
Lowrey
Pauline A
PA
Wraith
David C
DC
Elson
Christopher J
CJ
Barker
Robert N
RN
D020816:Amino Acid Motifs; D000744:Anemia, Hemolytic, Autoimmune / Q000209:etiology / Q000235:genetics / Q000276:immunology*; D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D001324:Autoantigens / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D001667:Binding, Competitive; D000949:Histocompatibility Antigens Class II / Q000378:metabolism; D016056:Immunodominant Epitopes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D051379:Mice; D008814:Mice, Inbred NZB; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011485:Protein Binding; D013601:T-Lymphocytes / Q000276:immunology*
D001457:Anion Exchange Protein 1, Erythrocyte; D001324:Autoantigens; D000949:Histocompatibility Antigens Class II; C024138:I-E-antigen; D016056:Immunodominant Epitopes; D010446:Peptide Fragments