Adaptive immune response can be divided into three stages:
1. Recognition stage: T cells and B cells are accurately identified by TCR and BCR respectively antigen Where the antigen recognized by T cells must be Antigen presenting cells To submit; 2. Activation and proliferation stage: after antigen recognition lymphocyte stay Costimulatory molecule The activation, proliferation, differentiation and Effector cell (such as killer T cells), effector molecules (such as antibodies cell factor ）And memory cells; 3. Effect stage: antigen is cleared by effector cells and molecules [1] 。
According to the characteristics, acquisition form and effect mechanism of immune response recognition, it can be divided into Innate immunity (inner immunity) and Adaptive immunity (adaptive immunity). The innate immunity is also called Innate immunity or Nonspecific immunity , also known as adaptive immunity Acquired immunity or Specific immunity [1] 。 Specific immunity
Compared with innate immunity, specific immune response has three main characteristics:
1. Specificity: Specificity refers to a specific antigen Stimulation can be obtained from immune system The corresponding T cell or B cell clone is selected from the lymphocyte bank, and the combination of lymphocytes with the corresponding antigen is highly specific; Diversity refers to the high heterogeneity of T cell bank or B cell bank, which is the sum of many specific antigen cell clones, giving the body the ability to recognize and react with a large number of antigen species in the surrounding environment. 2. Tolerance: In the embryonic stage, the self tissue composition and the corresponding lymphocyte When clones meet, these lymphocyte clones are deleted or forbidden. After birth, these clones lose their responsiveness to their own tissue components, that is immune tolerance However, the ability to recognize and respond to "non self" antigens is well preserved. The mechanism of immune tolerance is the key for the immune system to distinguish itself from others. 3. Memory: Both T cells and B cells will produce abnormal immune responses antigen Stimulate activation and proliferation lymphocyte Differentiated memory cells, which are different from the initial (or non sensitized) lymphocytes, can respond when encountering the same antigen again incubation period Short, strong and long lasting re immune response [1] 。 Innate immunity
Inherent immunity is gradually formed in the long-term evolution of organisms, and is the first line of defense against pathogen invasion. Cells involved in innate immunity, such as monocyte macrophages dendritic cell 、 Granulocyte 、 NK cells And NK T cells, which recognize the immunogen T cell and B cell It has a high degree of specificity, but can be pattern recognition receptor De identification Pathogenic Microbes The expressed structure is called pathogen related model molecule. [1] It is characterized by: (1) no specificity and wide application; (2) Congenital possession; (3) Initial vs antigen Contact can exert effect, but it has no memory; (4) Stable heredity; (5) There is little difference between normal individuals of the same species. Nonspecific immunity It is the first immune defense line of the body and the basis of specific immunity. Relationship between two kinds of immunity
Innate immunity and Adaptive immunity They are complementary and inseparable. Inherent immunity is often a prerequisite for adaptive immunity, such as dendritic cell and Phagocyte Phagocytosis of pathogenic organisms is actually a process and presentation antigen The process of adaptive immune response provides conditions for the recognition of adaptive immune response. The effector molecules of adaptive immune response can greatly promote the innate immune response. For example, antibodies can promote the phagocytosis of phagocytes, which is called regulating phagocytosis or promoting the cytotoxicity of NK cells; For example, many of them are secreted by T cells cell factor It can promote the maturation, migration and killing function of cells involved in innate immune response [1] 。 There are several differences between innate immunity and adaptive immune response.
1. In the form of acquisition: the innate immunity is inherent or congenital, without antigen It can be obtained by stimulating. However, adaptive immune response is acquired, which must be acquired after contacting with antigen. 2. Effective time: the innate immunity can play its role quickly (several minutes to 4 days) at the early stage of antigen appearance. The adaptive immune response needs to play a role in 4-5 days.
3. The innate immunity is pattern recognition receptor ； Adaptive immune response is a specific recognition antibody, and it produces diversity due to gene rearrangement during cell development. 4. Inherent immunity without immune memory; Adaptive immunity It has immune memory and produces memory cells. 5. Inherent immunity includes bacteriostatic substances, bactericidal substances complement 、 Inflammatory factors 、 Phagocyte , NK cells NK T cells 。 Adaptive immunity includes T cells and B cells [1] 。 
