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Dedicated antigen-presenting cells, including macrophages, B cells and dendritic cells, present foreign antigens to helper T cells, while virus-infected cells (or cancer cells) can present antigens originating inside the cell to cytotoxic T cells. In addition to the MHC family of proteins, antigen presentation relies on other specialized ...
When a naïve or memory B cell is activated by an antigen, it proliferates and differentiates into an antibody-secreting effector cell, known as a plasmablast or plasma cell. [2] In addition, B cells present antigens (they are also classified as professional antigen-presenting cells, APCs) and secrete cytokines. [1]
Because T cells recognize only fragmented antigens displayed on cell surfaces, antigen processing must occur before the antigen fragment can be recognized by a T-cell receptor. Specifically, the fragment, bound to the major histocompatibility complex (MHC), is transported to the surface of the antigen-presenting cell, a process known as ...
The latter case induces recognition by antigen-specific Th2 cells or Tfh cells, leading to activation of the B cell through binding of TCR to the MHC-antigen complex. It is followed by synthesis and presentation of CD40L (CD154) on the Th2 cell, which binds to CD40 on the B cell, thus the Th2 cell can co-stimulate the B cell. [11]
Each B cell and T cell is specific for a particular antigen, which simply means that each of these cells is able to bind to a particular molecular structure (such as an antigen). The specificity of binding resides in a specific receptor for antigen: the B-cell receptor (BCR) and the T-cell receptor (TCR) for B and T cells, respectively. Both ...
Naïve B cells circulate through follicles in secondary lymphoid organs (i.e. spleen and lymph nodes) where they can be activated by a floating foreign peptide brought in through the lymph or by antigen presented by antigen-presenting cells (APCs) such as dendritic cells (DCs). [5]
The T cell-dependent processes are subdivided into primary and secondary responses: a primary response (meaning that the T cell is present at the time of initial contact by the B cell with the antigen) produces short-lived cells that remain in the extramedullary regions of lymph nodes; a secondary response produces longer-lived cells that ...
Function of T helper cells: Antigen-presenting cells present antigens on their Class II MHC molecules . Helper T cells recognize these by expressing the CD4 co-receptor . The activation of a resting helper T cell causes it to release cytokines and other signals (green arrows) that stimulate the activity of macrophages , killer T cells , and B ...