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. Author manuscript; available in PMC: 2018 Apr 1.
Published in final edited form as: Transplantation. 2017 Apr;101(4):704–712. doi: 10.1097/TP.0000000000001588

FIGURE 1. T cell dependent B cell activation via Mutiple T-B interations after allostimulation.

FIGURE 1

Naïve mature B cells are activated through BCR recognition (signal 1) and migrate to the T-B border via HEVs (High Endothelial Venules). Primed B cells receive further signals from costimulation (signal 2), and cytokines (signal 3) in the T-B border. Some activated CD4 T cells can acquire charateristics of Tfh cell lineage and migrate into the B cell follicle via CXCR5. These Tfh cells provide IL-21 and costimulation and induce the proliferation of cognate B cells, isotype switching, and somatic mutation. This massive B cell expansion and differentiation leads to the formation of hyperplastic germinal center in the B cell follicle. Tfr cells and CD8 Treg cells are thought to suppress this germinal center response either directly, by depleting B cells or indirectly by modulating Tfh cells. The germinal center response induces the differentiation of isotype-switched affinity mature B cells into memory B cells or into long-lived plasma cells.