T cell autoimmunity in Ig transgenic mice.

Area of Science:

• Immunology
• Autoimmunity
• Molecular Biology

Background:

• Autoantibodies against U1/Sm ribonucleoprotein (snRNP) are hallmarks of systemic lupus erythematosus (SLE).
• The MRL murine model exhibits these characteristic autoantibodies, making it a relevant model for SLE research.

Purpose of the Study:

• To investigate the function of transgenic B lymphocytes in regulating autoreactive T cells against the snRNP autoantigen.
• To understand the mechanisms underlying T cell activation in the context of autoimmunity.

Main Methods:

• Development of transgenic mice expressing an Ig heavy chain specific for the D protein of murine snRNP.
• Analysis of B lymphocyte phenotype (immature, heat-stable Ag high).
• Examination of T lymphocyte responses using recombinant snRNP D protein and antigen-presenting cells (APCs).

Main Results:

• Transgenic anti-snRNP B cell APCs effectively stimulated CD4 T cells from wild-type C57BL/6 and MRL lpr/lpr mice.
• Non-specific APCs failed to elicit a similar T cell response, indicating the importance of antigen specificity.
• snRNP-reactive T cells in C57BL/6 transgenic mice showed tolerance, unlike those in MRL lpr/lpr transgenic mice.

Conclusions:

• Autoreactive T cells are present but not deleted in wild-type mice, with activation facilitated by autoantigen-specific APCs.
• Autoreactive B lymphocytes play a significant role in the in vivo activation and/or diversification of autoreactive T cells.
• Differences in tolerance induction between C57BL/6 and MRL lpr/lpr transgenic mice suggest distinct regulatory pathways in autoimmunity.