Relationship between target antigens and major histocompatibility complex (MHC) class II genes in producing two pathogenic antibodies simultaneously

Abstract

In this report,we present 15 patients with histological and immunopathologically proven pemphigus vulgaris (PV). After a mean of 80 months since the onset of disease, when evaluated serologically, they had antibodies typical of PV and pemphigoid (Pg). Similarly, 18 patients with bullous pemphigoid (BP) and mucous membrane pemphigoid (MMP) were diagnosed on the basis of histology and immunopathology.After a mean of 60 months since the onset of disease, when their sera were evaluated they were found to have Pg and PV autoantibodies. In both groups of patients the diseases were characterized by a chronic course, which included several relapses and recurrences and were non-responsive to conventional therapy. The major histocompatibility complex class II (MHC II) genes were studied in both groups of patients and phenotypes associated typically with them were observed. Hence, in 33 patients, two different pathogenic autoantibodies were detected simultaneously. The authors provide a computer model to show that each MHC II gene has relevant epitopes that recognize the antigens associated with both diseases. Using the databases in these computer models, the authors present the hypothesis that these two autoantibodies are produced simultaneously due to the phenomena of epitope spreading.

Fig. 1

Indirect immunofluorescence using monkey oesophagus as substrate. (a) Binding of sera of a pemphigus vulgaris (PV) patient to intercellular cement substance (ICS) (keratinocyte cell surface) (indicated by the white arrows). (b) Binding of sera of a pemphigoid (Pg) patient to basement membrane zone (BMZ) (indicated by the white arrows). (c) Binding of the sera of a patient with dual diagnosis to both BMZ and ICS (indicated by the white arrows).

Fig. 2

Predicted T cell epitopes. Figure depicts potential T cell epitopes that were predicted to be restricted by either human leucocyte antigen D-related (HLA-DR)β1*0402 (green) or HLA-DQβ1*0301 (yellow) from bullous pemphigoid antigen 2 (BPAG 2, BP180) (a), integrin alpha chain, alpha 6 isoform (b) and Dsg 3 (c). T cell epitopes that are predicted to be restricted by both HLA II molecules, HLA-DRβ1*0402 and HLA-DQβ1*0301, are shown in red. All the T cell epitopes shown in the figure have a binding score above the binding threshold (see Material and methods for details).

Fig. 2

Predicted T cell epitopes. Figure depicts potential T cell epitopes that were predicted to be restricted by either human leucocyte antigen D-related (HLA-DR)β1*0402 (green) or HLA-DQβ1*0301 (yellow) from bullous pemphigoid antigen 2 (BPAG 2, BP180) (a), integrin alpha chain, alpha 6 isoform (b) and Dsg 3 (c). T cell epitopes that are predicted to be restricted by both HLA II molecules, HLA-DRβ1*0402 and HLA-DQβ1*0301, are shown in red. All the T cell epitopes shown in the figure have a binding score above the binding threshold (see Material and methods for details).

Fig. 2

Predicted T cell epitopes. Figure depicts potential T cell epitopes that were predicted to be restricted by either human leucocyte antigen D-related (HLA-DR)β1*0402 (green) or HLA-DQβ1*0301 (yellow) from bullous pemphigoid antigen 2 (BPAG 2, BP180) (a), integrin alpha chain, alpha 6 isoform (b) and Dsg 3 (c). T cell epitopes that are predicted to be restricted by both HLA II molecules, HLA-DRβ1*0402 and HLA-DQβ1*0301, are shown in red. All the T cell epitopes shown in the figure have a binding score above the binding threshold (see Material and methods for details).