Plasma cells negatively regulate the follicular helper T cell program

Area of Science:

• Immunology
• Cell Biology

Background:

• B lymphocytes differentiate into antibody-secreting plasma cells, guided by follicular helper T (T(FH)) cells.
• T(FH) cells are crucial for adaptive immunity, orchestrating B cell responses.

Purpose of the Study:

• To investigate the immunoregulatory role of plasma cells beyond antibody secretion.
• To explore whether plasma cells can modulate T(FH) cell activity.

Main Methods:

• Analysis of antigen presentation machinery in isotype-switched plasma cells.
• In vivo studies assessing antigen presentation by plasma cells to T cells.
• Evaluation of T(FH) cell function in the presence and absence of plasma cells.

Main Results:

• Plasma cells express MHC class II, CD80, and CD86, enabling antigen presentation.
• Antigen-specific plasma cells can process and present antigens to induce T cell functions.
• Plasma cells inhibit IL-21 and Bcl-6 expression in T(FH) cells, acting as a negative feedback loop.
• Mice lacking plasma cells exhibit altered T(FH) cell activity.

Conclusions:

• Plasma cells engage in antigen presentation, influencing T(FH) cell responses.
• Plasma cell-mediated antigen presentation represents a novel regulatory mechanism limiting T(FH) cell activity.
• This finding uncovers a new layer of immune regulation in humoral immunity.