Major Histocompatibility Complex II (MHC II)

Major Histocompatibility Complex II (MHC II) are molecules found on certain immune cells, such as macrophages and other antigen-presenting cells. They play a key role in the immune system by displaying fragments of foreign substances (like bacteria or viruses) on the cell surface. This presentation helps other immune cells, called T-helper cells, recognize and respond to threats, triggering an immune response to fight infections. Essentially, MHC II molecules act as messengers, alerting the immune system to the presence of invaders and coordinating defense actions.