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Dendritic cells are a type of antigen-presenting cell (APC) that form an important role in the adaptive immune system. The main function of dendritic cells is to present antigens and the cells are therefore sometimes referred to as “professional” APCs.
In addition, only the dendritic cells have the capacity to induce a primary immune response in the inactive or resting naïve T lymphocytes. To do this, the dendritic cells capture the antigens from invading bodies, which they process and then present on their cell surface and presented, along with the necessary accessory or co-stimulation molecules.
Dendritic cells also contribute to the function of B cells and help maintain their immune memory. Dendritic producing cytokines and other factors that promote B cell activation and differentiation. After an initial antibody response has occurred due to an invading body, dendritic cells found in the germinal centre of lymph nodes seem to contribute to B cell memory by forming numerous antibody-antigen complexes. This is to provide a long lasting source of antigen that the B cells can take up themselves and present to T cells.
Dendritic cells are found in tissue that has contact with the outside environment such as the over the skin (present as Langerhans cells) and in the linings of the nose, lungs, stomach and intestines. Immature forms are also found in the blood. Once activated, dendritic cells move to the lymph tissue to interact with to interact with T cells and B cells and help shape the adaptive immune response. During development, they develop branched projections called “dendrites”, which is why the cells are so named.
Dendritic cells were first described by Ralph Steinman in the 1970’s. He found these cells in the spleen and it was later discovered that the cells were present in all lymphoid and most non-lymphoid tissues. Before this, immunologists generally thought that macrophages were the main APC in the immune system. Compared with dendritic cells, macorphages were present in much greater numbers, were evenly spread throughout the body and had were known to present antigens. As dendritic cells were relatively rare, itt took until the 1980’s for them t become accepted as professional APCs.