Search results
Results from the WOW.Com Content Network
Different antibodies have the potential to discriminate among specific epitopes present on the antigen surface. A hapten is a small molecule that can only induce an immune response when attached to a larger carrier molecule, such as a protein. Antigens can be proteins, polysaccharides, lipids, nucleic acids or other biomolecules. [4]
An antigen-presenting cell (APC) or accessory cell is a cell that displays an antigen bound by major histocompatibility complex (MHC) proteins on its surface; this process is known as antigen presentation. T cells may recognize these complexes using their T cell receptors (TCRs). APCs process antigens and present them to T cells.
Antigens generated endogenously within these cells are bound to MHC-I molecules and presented on the cell surface. This antigen presentation pathway enables the immune system to detect transformed or infected cells displaying peptides from modified-self (mutated) or foreign proteins. [5] [6]
Thus the progeny of a single B cell can produce antibodies, all specific for the same antigen, but with the ability to produce the effector function appropriate for each antigenic challenge. Class switching is triggered by cytokines; the isotype generated depends on which cytokines are present in the B cell environment. [77]
The endogenous pathway is used to present cellular peptide fragments on the cell surface on MHC class I molecules. If a virus had infected the cell, viral peptides would also be presented, allowing the immune system to recognize and kill the infected cell. Worn out proteins within the cell become ubiquitinated, marking them for proteasome ...
Plasma cells can only produce a single kind of antibody in a single class of immunoglobulin. In other words, every B cell is specific to a single antigen, but each cell can produce several thousand matching antibodies per second. [14] This prolific production of antibodies is an integral part of the humoral immune response. [citation needed]
These factors are usually produced by the newly activated T helper cell. [22] However, this activation occurs only after the B cell receptor present on a memory or a naive B cell itself would have bound to the corresponding epitope, without which the initiating steps of phagocytosis and antigen processing would not have occurred.
It is in this way, the MHC class I-dependent pathway of antigen presentation, that the virus infected cells signal T-cells that abnormal proteins are being produced as a result of infection. The fate of the virus-infected cell is almost always induction of apoptosis through cell-mediated immunity, reducing the risk of infecting neighboring ...