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The immune system consists of the lymphoid tissues of the organism and includes: bone marrow, lymph nodes, the spleen, thymus, tonsils, and parts of the digestive tract.
When the immune system detects a foreign particle (antigen), it responds by producing proteins called antibodies that destroy the harmful substances. The immune response also includes phagocytosis, which is the destruction of bacteria and other foreign substances by the white blood cells by internalizing and subsequently destroying them. Proteins called "complement" help in this process.
Immune system disorders occur when the system is not working well and does not fight tumours or harmful substances as it should. In these cases, the immune response is excessive or deficient.
