Pathogen/Antigen B CellsTyAntigen-Presenting Cells Memory B CellsPlasma Cells An
ID: 269682 • Letter: P
Question
Pathogen/Antigen B CellsTyAntigen-Presenting Cells Memory B CellsPlasma Cells Antigen+TH TH Antibody Secretion represented in the model above, B cells are activated by direct contact with antigens or stimulated helper T cells (Ty). Based on the model, which of the following best describes an outcome of B cell activation? (A) Activated B cells differentiate into plasma cells and memory cells (B) Activated B cells stimulate Ty cells to secrete antibodies (C) Both B cells and Ty cells release chemical signals that negatively regulate antigen-presenting cells (D) Plasma cells produce antibodies that activate additional B cells by a positive feedback mechanism.Explanation / Answer
Q.24 Answer is A - activated B cells differentiate into plasma cells and memory cells,
B cell activation require 2 signals. B cell binds with soluble antigen, internalize it, processes antigen and presents it to Th cells.Th cells whose TCR are specific for that peptide - MHC complex,recognize it and bind to B cells Via TCR-MHC interactions and some adhesion molecules. once triggered via TCR, Th cell expresses CD40 ligand for the molecule CD40 on B cell. CD40 ligand and CD40 molecule interaction triggers B cell activation and activated B cell co-stimulate Th cell via CD28. Activated Th cells produces cytokines responsible for proliferation of B cells. so B cells proliferate to produce clones of large number of daughter cells. Some of these daughter cells serve as memory cells and others get differentiated into plasma cells which secrete large quantity of specific antibody. This is how B cells are activated and proliferated.