B Cell (B Lymphocyte)
A type of white blood cell that produces antibodies targeting specific pathogens. B cells are part of adaptive immunity and play roles in autoimmune diseases when they produce autoantibodies. Anti-drug antibody production against therapeutic peptides involves B cell activation.
Technical Context
B cells mature in the bone marrow and are activated in secondary lymphoid organs (lymph nodes, spleen) when their B cell receptor (surface-bound antibody) encounters matching antigen. With T cell help (Tfh cells providing CD40L co-stimulation and IL-21/IL-4 cytokines), activated B cells undergo: clonal expansion, somatic hypermutation (refining antibody affinity in germinal centres), class switch recombination (switching from IgM to IgG, IgA, IgE, or IgD), and differentiation into antibody-secreting plasma cells and memory B cells. Anti-drug antibodies (ADAs) against therapeutic peptides are produced by this pathway — the peptide drug (as a foreign protein) is processed by antigen-presenting cells, stimulates T helper cells, which in turn activate B cells specific for the peptide. Strategies to reduce ADA formation include: humanising peptide sequences, removing T cell epitopes (deimmunisation), and using tolerogenic formulations.