B-cell activation and the germinal centre reaction
T-dependent B-cell activation & the germinal centre reaction. A B cell that has captured antigen through its BCR receives help from a T follicular helper (Tfh) cell — CD40L, ICOS and cytokines IL-4 / IL-21 — triggering the germinal centre, where AID drives class-switch and affinity maturation before B cells become plasma or memory cells. Click any protein for the matching Assay Genie In Vivo functional-grade antibody or ELISA kit.
High-affinity antibody responses to protein antigens are T-dependent. A naive B cell binds antigen through its B-cell receptor (BCR), signalling via CD79, SYK, BTK and PLCγ2 to activate NF-κB; the CD19 co-receptor lowers the threshold. The B cell then presents antigen on MHC-II to a T follicular helper (Tfh) cell and receives help: CD40L→CD40 (a second NF-κB signal), ICOS/ICOSL co-stimulation, and the cytokines IL-4 (→STAT6) and IL-21 (→STAT3).
These signals launch the germinal centre. BCL6 enforces the GC-B-cell programme; AID (AICDA) mediates class-switch recombination and somatic hypermutation, generating diversified, higher-affinity antibodies that are selected in the light zone. A fate switch governed by mutually antagonistic transcription factors — BCL6 and PAX5 versus IRF4 and BLIMP1 (PRDM1) — then directs output to antibody-secreting plasma cells or long-lived memory B cells.
Assay Genie In Vivo functional-grade antibodies interrogate this pathway: deplete B cells (anti-CD19, anti-B220), block T–B help (anti-CD40, anti-ICOS) and modulate cytokines (anti-IL-4). For research use only; not for diagnostic or therapeutic procedures. Mouse targets shown.
Every protein node links to a product: surface / cytokine targets open Assay Genie In Vivo antibodies; signalling proteins open the matching ELISA kit.