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T FH cells in bystander and cognate interactions with B cells
Author(s) -
Wan Zurong,
Lin Yihan,
Zhao Yongshan,
Qi Hai
Publication year - 2019
Publication title -
immunological reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.839
H-Index - 223
eISSN - 1600-065X
pISSN - 0105-2896
DOI - 10.1111/imr.12747
Subject(s) - germinal center , cd40 , microbiology and biotechnology , bystander effect , biology , naive b cell , antigen , b cell , b cell receptor , cognate , antigen presenting cell , immunology , t cell , immune system , cytotoxic t cell , antibody , in vitro , genetics , linguistics , philosophy
Summary Follicular T‐helper ( T FH ) cells play a crucial role in three aspects of the germinal center ( GC ) response. They promote GC formation, arbitrate competition among GC B cells to determine the outcome of affinity maturation, and regulate GC output of memory and plasma cells to shape the long‐lived humoral immune memory. Of fundamental importance are dynamic physical interactions between T FH and B cells, which are the main platform for T FH cells to deliver “help” factors to B cells and also for reciprocal signaling from B cells to maintain the helper state of T FH cells. Recent work has significantly expanded our understanding of how T‐B interactions are spatiotemporally regulated and molecularly orchestrated to fulfill those T FH functions. In this review, we elaborate two modes of T‐B interactions, the antigen‐specific or cognate mode in which T FH cells engage individual antigen‐presenting B cells and the antigen nonspecific bystander mode in which T FH cells are engaged with the ensemble of follicular B cells. We discuss findings that indicate how short‐lived cognate T‐B contacts coupled with an intercellular positive feedback drive affinity‐based selection and how bystander interactions between T and B cells regulate follicular T‐cell recruitment and maintenance of an appropriate helper state. We argue that this combination of bystander and cognate interactions with B cells constantly shapes the internal state of T FH cells and provides the platform to execute their helper functions.