Follicular Dendritic Cells - Interaction With B-cells

Interaction With B-cells

To generate the follicular structures, FDCs need to be stimulated by lymphotoxin, a mediator produced by B cells. Also, noncognate B cells play a significant role as an antigen transporter to FDCs. They capture immune complexes in CR1/2-dependent way either directly from the blood or from macrophages, and putate to the lymphoid tissue, where they upload FDCs with opsonized antigen. FDCs, in turn, attract B cells with chemoattractant CXCL13. B cells lacking CXCR5, the receptor for CXCL13, still enter the white pulp, but are mislocalized and disorganized. The stimulation of CXCR5 on B cells upregulates LT production, which leads to FDCs activation and stimulates further CXCL13 secretion, thus generating a positive feed-forward loop. This results in the formation of GC, where antigen-activated B cells are trapped to undergo somatic mutation, positive and negative selection, isotype switching and differentiation into high-affinity plasma cells and memory B cells. The adhesion between FDCs and B cells is mediated by ICAM-1 (CD54)-LFA-1(CD11a) and VCAM-VLA-4 molecules. Activated B-cells with low affinity to antigen captured on FDCs surface as well as autoreactive B-cells undergo apoptosis, whereas B cells bound to FDCs through the antigen complex, survive due to apoptosis blockage caused by interaction with FDCs.