Enfeksiyondan korunma ve immün sistem

Immune system is a sum of all processes which protect a living organism against diseases, also recognize, and destroy pathogens and tumor cells. Human body protects itself against bacteria, viruses, and other foreign substances via very diverse mechanisms. This protection involves physical barriers, fagocytic cells in blood, and tissues, and various molecules of hematologic origin. These mechanisms can be divided into two interdependent defense systems as non-specific or hereditary immune system and specific or acquired immune system. Non-specific immune system which is the first stage of the defense system discriminates between foreign substances and those belonging to the body, but it cannot distinguish between two types of pathogens. However, specific immune system can discern between those belonging or foreign to the organism, and responds specifically to different pathogens, and foreign molecules. The main objective of this paper is in general to deal with cells, molecules, and tissues involving in immune system, and define normal mechanisms used to defend the body against foreign substances.