Immunochemistry PDF

# Immunochemistry ## Definition Immunochemistry is a branch of chemistry that involves the study of the molecular mechanisms underlying the function of the immune system, especially the nature of antibodies, antigens and their interactions. ## Immunity - It is defined the resistance offered by...

# Immunochemistry ## Definition Immunochemistry is a branch of chemistry that involves the study of the molecular mechanisms underlying the function of the immune system, especially the nature of antibodies, antigens and their interactions. ## Immunity - It is defined the resistance offered by the host to toxic molecules, micro organisms and foreign body. ## Types of Immunity A diagram shows the following types of immunity - **Innate** (inborn) - Genetic factors - **Acquired** - **Active**: Own antibodies - **Natural**: Exposure to infectious agent - **Artificial**: Immunization - **Passive**: Ready-made antibodies - **Natural**: Maternal antibodies - **Artificial**: Antibodies from other sources ## Innate Immunity - Innate immunity refers to nonspecific defence mechanisms and is basic immunity which may be genetically passed from one generation to next generation. - These mechanisms include physical barriers such as skin, chemicals in the blood, and immune system cells that attack foreign cells in the body. ### It may be, - **Species immunity** - Individuals in the same species exhibit uniform pattern of susceptibility to different infections. - **Racial immunity** - Within one species, different races shows difference in resistance. - **Individual immunity** - Different individuals of the same species and races show variation to infection. ## Factors Affecting Immunity - AGE - NUTRITION - HORMONAL INFLUENCES ## Mechanism The innate immunity acts in two levels: 1. Epithelial surface level 2. Chemical secretions 3. Cellular factors ### Epithelial surface level - **Skin**: Sebaceous glands secrete sebum which contains both saturated and unsaturated fatty acids and they kills the micro organism - **Conjunctiva**: Lysozyme which is present in the tear acts against the micro organism - **Nose, naso pharynx and respiratory tract**: The mucus present in the respiratory tract will absorb all the dust particles and preventing the entrance to lungs. - **Mouth, stomach and intestinal tract**: - Saliva secreted by the salivary gland had a mild bactericidal action. - In stomach the high acidity will prevent the growth of micro organism. ### Chemical secretions - The oil and sweat produced by skin glands contains fatty acid and lactic acid which are bactericidal in action. - Lysozymes present in sweat and tears contribute antibacterial activity. - HCL of stomach, properdin, leukins and beta lysine like substances present in serum have the same bactericidal action. ### Cellular factors - Blood cells - Macrophages - Inflammatory reaction - Fever - Interferons - Natural killer cells - Complement system #### Blood cells - White blood cells (WBCs), also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. - Neutrophils performs phagocytosis and destroy micro organisms. - Basophils release histamine that plays a role in inflammatory reaction. - Monocytes of blood changes to macrophages at the time of infection and shows phagocytic action. #### Macrophages - Macrophages are the transformed forms of monocytes. Later they are increasing in size, and destroys the foreign particles by phagocytosis. #### Inflammatory reaction - In case of cuts, wounds and injuries the microbes get entered to the body. - These microbes release certain chemicals in the body. - The basophils release histamin and causes the dialation of capillaries in the affected area and increases their permeability. - As a result more blood rushed to the affected area and imparts it warmth and redness. - The plasma leaks to the affected tissue spaces and dialutes the toxin released by the microbes and decreases their toxicity. #### Fever - The mechanism of fever appears to be a defensive reaction by the body against infectious disease. - When bacteria or viruses invade the body and cause tissue injury, one of the immune system's responses is to produce pyrogens. - These chemicals are carried by the blood to the brain, where they disturb the functioning of the hypothalamus, the part of the brain that regulates body temperature. - The pyrogens inhibit heat-sensing neurons and excite cold-sensing ones, and the altering of these temperature sensors deceives the hypothalamus into thinking the body is cooler than it actually is. - In response the hypothalamus raises the body's temperature above the normal range, thereby causing a fever. The above-normal temperatures are thought to help defend against microbial invasion because they stimulate the motion, activity, and multiplication of white blood cells and increase the production of antibodies. - At the same time, elevated heat levels may directly kill or inhibit the growth of some bacteria and viruses that can tolerate only a narrow temperature range. #### Interferons - In case of viral infections, the cells invaded by a virus produces an antiviral protein called interferons. - The interferons make the neighbouring cells resistant against viral infections. #### Natural killer cells - These are the type of lymphocytes which kills the infected cells and checks the spread of infection. #### Complement system - It is a system of 30 proteins present in the serum. These proteins defend the body by different ways, like by strengthening phagocytic and inflammatory reactions and by rupturing the cell membranes of the microbes. ## Active Immunity - The immunity which results from the production of antibodies by the immune system in response to the presence of an antigen. - Its of two types: - Natural active immunity - Artificial active immunity ### Natural active immunity - When there is repeated exposure to a specific type of micro organism the resistance will develop against the organism and is called as Natural active immunity ### artificial active immunity - It's the immunity that is mainly acquired through the vaccination method. ## Passive Immunity - It's the immunity that is induced in the persons body by the transfer of readymade antibodies against infective agents. - It may also be: - Natural passive immunity - Artificial passive immunity ### Natural passive immunity - It's the resistance passively transferred from mother to fetus through placenta. - IgG antibodies can cross the placental barrier to reach the fetus. ### Artificial passive immunity - It's the resistance passively transferred to recipient by the parenteral administration of antibodies. ## Mechanism - This mechanism defends the body against specific micro organisms by the activation of immune system. ## Events.. - **Cells of the immune system:** - Lymphocytes: the T- lymphocytes and B-lymphocytes are the basis of immune system. - Antigen presenting cells: these are the specialized cells which includes macrophages. - **Types of immune system:** - Humoral immunity, also called the antibody-mediated immune system, is the aspect of immunity that is mediated by macro molecules found in extracellular fluids such as secreted antibodies, complement proteins, and certain antimicrobial peptides. - Cell mediated immunity: Cell mediated immunity is an immune response that does not involve antibodies, but rather involves the activation of phagocytes and antigen-specific cytotoxic T-lymphocytes. - **Types of immune response:** - Primary immune response: when the body comes in contact with an antigen for the first time, the response is called Primary immune response. - Secondary immune response: it occurs when body comes in contact with the same antigen again.