T_FH cells in bystander and cognate interactions with B cells

Area of Science:

• Immunology
• Cellular Biology
• Molecular Biology

Background:

• Follicular T-helper (T_FH) cells are critical for germinal center (GC) responses, influencing GC formation, B cell affinity maturation, and the generation of memory and plasma cells.
• Dynamic physical interactions between T_FH and B cells are essential for T_FH cell-mediated help and reciprocal B cell signaling that sustains T_FH cell function.

Purpose of the Study:

• To review and elaborate on the two primary modes of T_FH-B cell interactions: antigen-specific (cognate) and antigen-nonspecific (bystander).
• To discuss how these interactions are spatiotemporally regulated and molecularly orchestrated to fulfill T_FH cell functions in humoral immunity.

Main Methods:

• This review synthesizes recent findings on T_FH-B cell interactions.
• Analysis of molecular mechanisms and spatiotemporal regulation governing T_FH cell functions.

Main Results:

• Cognate T-B cell interactions, characterized by short-lived contacts and positive feedback, drive affinity-based B cell selection.
• Bystander interactions regulate follicular T-cell recruitment and maintain the T_FH helper state.
• A combination of cognate and bystander interactions shapes T_FH cell internal states and facilitates helper functions.

Conclusions:

• T_FH-B cell interactions are multifaceted, involving both direct, antigen-specific engagement and broader, antigen-nonspecific interactions.
• These distinct interaction modes are crucial for effective B cell maturation, selection, and the establishment of long-lived humoral immune memory.