HLA polymorphisms and T cells in rheumatoid arthritis

Area of Science:

• Immunology
• Rheumatology
• Genetics

Background:

• Rheumatoid arthritis (RA) is characterized by immune cell infiltration in the synovial membrane, forming structures resembling secondary lymphoid tissues.
• T cells are implicated in RA pathogenesis, with HLA genes being a significant risk factor, particularly HLA-DRB1.
• The diverse T cell receptor repertoire in RA infiltrates, including clonally expanded populations, suggests a complex immune response.

Purpose of the Study:

• To investigate the role of T cells and HLA genes in rheumatoid arthritis pathogenesis.
• To explore the systemic nature of rheumatoid synovitis and identify potential antigens driving the immune response.

Main Methods:

• Analysis of T cell infiltrates in synovial membranes.
• Investigation of HLA gene associations with RA risk, progression, and severity.
• Studies using T cell receptor transgenic animal models.

Main Results:

• Clonally expanded CD4 T cell populations with deficient CD28 expression and autoreactivity were identified in RA patients.
• These autoreactive T cells are not confined to the joint, suggesting a systemic autoimmune process.
• T cell responses to ubiquitously expressed self-MHC molecules in animal models induce synovial inflammation.

Conclusions:

• Rheumatoid synovitis may be a manifestation of a systemic autoimmune disease, not solely a joint-specific condition.
• Widely distributed antigens, rather than joint-specific ones, likely drive the chronic immune response in RA.
• Understanding the systemic nature of RA is crucial for identifying pathogenic antigens and developing effective treatments.