| The immune system has evolved to protect us against infection with micro-organisms and to remove abnormal, diseased or damaged cells. Lymphocytes and other cells found in the reticuloendothelial system, the lymph glands, bone marrow, liver and spleen engulf and destroy any 'foreign' (non-body) cells, such as micro-organisms and defective or damaged body cells by a process known as phagocytosis |