B-cells

B cells are a major part of the body's immune system. They start off as lymphocytes and are then given their specific function inside the bone marrow. B cells work alongside T cells to protect the body from pathogens. When a pathogen enters the body, B and T cells leave the blood circulation and enter the lymph nodes where the adaptive immune response is intiated. The antigens of the pathogen enter the lyph node as a soluble antigen or carried by denditic cells.  B cells are antigen presenting cells and interact with the soluble antigens. B cells are partially activated when a soluble antigen belonging to a pathogen interacts with it's receptor. The B cell engulfs the antigen by endocytosis and then presents the antigen on it's own membrane. T cells then interact with these antigen presenting B cells via their T cell receptors. Once this happens the B cells are fully activated and proliferate into plasma cells and B memory cells. Plasma cells then secrete antibodies that recognise pathogens that have the specific antigen presented by the B cells previously. The B memory cells remain behind in case a second infection by the same pathogen attacks the body.