B lymphocyte differentiation in the mouse

When an antigen enters the body, it can react upon such an invasion with a nonspecific and a specific defense mechardsm. Phagocytic white blood cells can attack antigens, such as present on the surface of bacteria and viruses, non-specifically by engulfing and destroying these particles. The specific defense against foreign agents depends on the immune system of the individual and can be divided in cell-mediated and humoral immunity. Cell-mediated immune reactions can be defmed as those immunological reactions, which are transferable by cells and not by serum. Cellmediated immunity includes phenomena like allograft rejection, allogeneic disease, delayed hypersensitivity. and cell-mediated defense against viruses and fungi. The cell type which mediates this type of immune response is the lymphocyte, which is dependent on the thymus for its differentiation: the T lymphocyte. Another function of the T cell is a regulatory influence on humoral immunity. Some aspects of this function of the T lymphocyte will be discussed.