B cells are involved in the humoral immune response, whereas T cells are involved in cell-mediated immune response. Killer T cells only recognize antigens coupled to Class I MHC molecules, while helper T cells and regulatory T cells only recognize antigens coupled to Class II MHC molecules. These two mechanisms of antigen presentation reflect the different roles of the two types of T cell. A third, minor subtype are the γδ T cells that recognize intact antigens that are not bound to MHC receptors. The double-positive T cells are exposed to a wide variety of self-antigens in the thymus, in which iodine is necessary for its thymus development and activity. In contrast, the B cell antigen-specific receptor is an antibody molecule on the B cell surface and recognizes native (unprocessed) antigen without any need for antigen processing. Such antigens may be large molecules found on the surfaces of pathogens, but can also be small haptens (such as penicillin) attached to carrier molecule. Each lineage of B cell expresses a different antibody, so the complete set of B cell antigen receptors represent all the antibodies that the body can manufacture. When B or T cells encounter their related antigens they multiply and many "clones" of the cells are produced that target the same antigen. This is called clonal selection. Antigen presentation to T lymphocytes
Both B cells and T cells carry receptor molecules that recognize specific targets.
Asciminib, sold under the brand name Scemblix, is a medication used to treat Philadelphia chromosome-positive chronic myeloid leukemia (Ph+ CML). Asciminib is a protein kinase inhibitor.The most common adverse reactions include upper respiratory tract infections, musculoskeletal pain, fatigue, nausea, rash, and diarrhea.Asciminib was approved for medical use in the United States in October 2021, and in the European Union in August 2022.The U.S. Food and Drug Administration (FDA) granted the application for asciminib priority review, fast track, orphan drug, and breakthrough therapy designations. Mechanism of action
Asciminib is described as a "STAMP inhibitor," which means "specifically targeting the ABL myristoyl pocket." The wild-type ABL has a myristoylated N-terminus, which binds to an allosteric site, but the ABL fusion protein does not have the myristoylated domain. In the wild-type protein, when myristoylated N-terminus binds to the allosteric site, the kinase has reduced activity. Since the mutant fusion protein does not have the myristoylated N-terminus domain, it is not subject to this form of regulation, and thus the fusion protein is constitutively active. Asciminib binds to the allosteric site, resulting in an inhibition of bcr-abl activity.Unlike other bcr-abl inhibitors, such as imatinib, asciminib does not bind to the ATP-binding site on the active site of the enzyme. Asciminib and active site bcr-abl inhibitors have non-overlapping resistance mutations. The mutations A337V and P223S overcome the inhibitory activity of asciminib, but asciminib is not affected by the notorious T315I mutation that affects most ATP-competitive active site inhibitors, except ponatinib.