Antigen is a substance that can stimulate the body to produce immune response and can specifically bind with immune reaction products. The basic abilities of antigen are immunogenicity and reactivity. Immunogenicity refers to the ability to stimulate the body to form specific antibodies or sensitized lymphocytes. Reactivity refers to the ability to interact with immunoglobulin 2.
Animal proteins with antibody activity are glycoproteins produced by lymphocytes (B cells). It mainly exists in plasma, but also exists in other body fluids, tissues and some secretions. Most immunoglobulin in human plasma exists in the form of gamma globulin. It can be divided into five categories, namely immunoglobulin G(IgG), immunoglobulin A(IgA), immunoglobulin M(IgM), immunoglobulin D(IgD) and immunoglobulin E(IgE), as well as subclasses of IgG, IgA and IgM.
Step 3 supplement
Complement (C) is a group of active proteins in serum and tissue fluid of normal people and animals. As early as the end of 19, Bordet confirmed that fresh blood contains a heat-labile component, which can assist and supplement specific antibodies and mediate immune lysis and hemolysis, so it is called complement. At present, it is known that complement is a multi-molecular system composed of more than 30 soluble proteins, membrane-bound proteins and complement receptors, so it is called complement system. According to its biological function, the components of complement system can be divided into endogenous components, regulatory components and receptors (CR).
4. Cytokine
Cytokines (CK) is a kind of protein or small molecule polypeptide which can transmit information between cells and has immunomodulatory and effector functions.
5. Immune response
It is a physiological process in which the body's immune system stimulates antigens to eliminate antigens. This process is a comprehensive reflection of the physiological functions of various parts of the immune system, including antigen presentation, lymphocyte activation, immune molecule formation, immune effect and a series of physiological reactions. Through effective immune response, the body can maintain the stability of the internal environment.
6. Positive selection
When CD4+CD8+ double positive pre-T cells (thymocytes) effectively combine with MHC-II or I molecules on the surface of thymic cortical epithelial cells, they can be selected to continue to develop and differentiate into CD4+ or CD8+ "single positive" cells with TCR. Otherwise, apoptosis (apot~iB) will occur, which is a positive selection process. Through this selection, CD4 ++ or CD8+T cells gain the ability to recognize the antigen peptide -MHC-II or I complex, that is, the MHC limitation that determines the T cell response.
7.ADCC effect
The Chinese name of ADCC effect is "antibody-dependent cell-mediated cytotoxicity". Refers to the combination of antigen and antibody, which leads to the attack of cells with cytotoxic effect due to surface marking, and then removes the antigen.
When IgG antibody specifically binds to the epitope on the surface of target cell through Fab fragment, its Fc fragment can bind to FcγRIII on the surface of NK cell, thus making NK cell produce non-specific killing effect on target cell, that is, ADCC effect.
8. American Power Conference
The capture of foreign antigens by antigen presenting cells (APC) is mostly random, and they can also capture antigens through related antigen receptors. The ways of APC capturing antigen include phagocytosis, swallowing, adsorption and conditioning. The antigen is enzymatically decomposed into antigen peptide in the acidic environment of APC, and the antigen peptide combines with MHC-II molecules produced in APC cytoplasm to form antigen peptide-MHC-II molecular complex, which is transported and expressed on the surface of APC for recognition by CD4+TH cells.