Early cellular events in systemic autoimmunity driven by chromatin-reactive T cells

Area of Science:

• Immunology
• Autoimmunity
• Molecular Biology

Background:

• Exposure to lupus-inducing drugs like procainamide-hydroxylamine triggers T cell responses against chromatin.
• The origin and role of autoantibodies in drug-induced lupus remain unclear.
• Understanding B cell responses to T cells is crucial for elucidating autoimmune initiation.

Purpose of the Study:

• To identify the specificities of B cells responding to chromatin-reactive T cells.
• To investigate the role of Fas-mediated cell death in the expansion of autoreactive B cells.
• To determine if B cells can present chromatin-bound antigens to T cells.

Main Methods:

• Adoptive transfer of chromatin-reactive T cells into mice.
• Quantification of IgM and IgG anti-chromatin antibody-secreting B cells.
• Assessment of B cell antigen presentation capabilities in vitro.
• Analysis of B cell responses in mice with defective Fas (lpr allele).

Main Results:

• Adoptive transfer of chromatin-reactive T cells led to the emergence of IgM anti-chromatin B cells.
• B cell populations secreting anti-chromatin antibodies expanded significantly in mice with defective Fas.
• B cells could internalize DNA-bound proteins and present T cell epitopes.
• No direct binding of chromatin to anti-DNA antibodies was observed.

Conclusions:

• The study reveals that the immune system harbors autoreactive B cells capable of responding to T cell activation.
• Inhibition of Fas-mediated activation-induced cell death promotes the expansion of these autoreactive B cells.
• This highlights a potential mechanism for the development of autoimmunity, particularly in conditions like drug-induced lupus.