The immune system protects you against invading pathogens and infections that may enter your body. It can be broadly split into two streams - the adaptive and the innate immunity. The innate immunity is more broad and the first line of defence that is given generally by white blood cells (WBC) that circulate the body and look for foreign particles that are recognised in the body as 'non-self'. Once non-self material is recognised, an immune response is mounted resulting in the recruitment of multiple different cell types that work together to kill the foreign cells in the body. A specific cell known as a dendritic cell is responsible for taking up the foreign particles and expressing them on their own surface. This is responsible for stimulating the second branch of the immune system - adaptive immunity. This is more specific and specialised involving T cells which recognise the foreign material on the surface of dendritic cells and also mount an immune attack. In turn, B cells become activated and produce antibodies specific to the foreign material, contributing to the immune response to clear the foreign material from the body and furthermore, producing a memory against the foreign material so in future it can be cleared from the body more quickly.