Immunity and its types
- 1. Department of Microbiology Srishti Patel MSc. Final Year ( 3rd sem )
- 2. IMMUNITY ITS TYPES IMMUNITY Immunity can be defined as a complex biological system endowed ( provided ) with the capacity to recognize and tolerate whatever belongs to the self, and to recognize and reject what is foreign (non-self). TYPES OF IMMUNITY 1. Innate Immunity- The innate immune responses are the first line of defense against invading pathogens. They are also required to initiate specific adaptive immune responses. 2. Adaptive/Acquired Immunity- The adaptive immune system, is a subsystem of the immune system that is composed of specialized, systemic cells and processes that eliminate pathogens or prevent their growth.
- 3. CELLS IN INNATE AND ADAPTIVE IMMUNE SYSTEM
- 5. INNATE IMMUNITY INNATE IMMUNITY • Also know as Non- Specific Immunity and provides the first line of defense • Given by genetic makeup • Generates a fast inflammatory response that is generic to all types of pathogens or tissue damages and does not confer immune memory to the host. • initiated within hours and provides a rapid array of defenses TYPES OF DEFENSES/BARRIERS 1. The anatomical or chemical barriers- these include the skin, mucous membrane, gastro-intestinal tract, urino-genital tract and respiratory tract that are responsible of preventing the entry of pathogen or to trap the pathogen during its entry in the body. 2. The phagocytic barriers- these include the leukocytes present in blood that are capable of performing phagocytosis and killing the pathogen, for example, macrophages, neutrophils, natural killer cells. 3. Plasma proteins- plasma of the blood is rich in proteins that perform immnulogical functions, such as the complement proteins that inform phagocytic cells about a pathogen and also trigger production of antibodies. 4. Cytokines- these are the proteins produced by the epithelial cells (dendritic cells), neutrophils, macrophages that control the growth and spread of infection. CHARACTERISTICS & DEFENSES
- 6. INNATE IMMUNITY TYPES OF INNATE IMMUNITY 1. Species Immunity: Species immunity (species resistance) is that in which a disease affecting one species does not affect the other species. For convenience, humans do not contract cattle plague, chicken cholera, hog cholera, infectious horse anaemia, etc., while animals are not affected by many human diseases such as enteric fever, scarlet fever, syphilis, gonorrhoea, measles, etc. 2. Racial Immunity: Racial immunity (racial resistance) is that in which various races (breeds) show marked differences in their resistance to certain infectious diseases. A well known example is that Brahman cattle are resistant to the protozoan parasite responsible for tick fever in other breeds of cattle. Similarly, Black Africans affected by sickle cell anaemia, a genetic disease, are resistant to malaria while malaria affects other human races. 3. Individual Immunity: Having the same racial background and opportunity for exposure, some individuals of the race experience fewer or less severe infections than other individuals of the same race. For convenience, children are more susceptible to diseases such as measles and chicken pox, while aged individuals are susceptible to other diseases like pneumonia. TYPES
- 7. ACQUIRED IMMUNITY CHARACTERISTICS • Based upon resistance acquired during life • Relies on genetic events and cellular growth • Responds more slowly, over few days • Is specific- each cell responds to a single epitope on an antigen • Has anamnestic memory- repeated exposure leads to faster, stronger response • Leads to clonal expansion CHARACTERISTICS & CARDINAL FEATURES CARDINAL FEATURES 1. Tolerance to self antigens - under normal conditions, an immune response to "self" antigens (called an autoimmune response) does not occur. 2. Specificity – components of adaptive immunity react specifically with the antigen that induced their formation. 3. Memory - the adaptive immunological response remembers the antigen for invariable period of time and upon subsequent exposure to homologous antigen there is an anamnestic immune response, i.e. strengthens upon repeated exposure
- 10. ACQUIRED IMMUNITY ACQUIRED ACTIVE IMMUNITY Active immunity is created by our own immune system when we are exposed to a potential disease- causing agent (i.e., pathogen). Most of the time, we are exposed to these potential pathogens naturally throughout the course of our day — in the air we breathe, the food we eat, and the things we touch TYPES OF ACQUIRED ACTIVE IMMUNITY 1. NATURALLY ACQUIRED ACTIVE IMMUNITY- Naturally acquired active immunity occurs when the person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the primary immune response. Once a microbe penetrates the body’s skin, mucous membranes, or other primary defenses, it interacts with the immune system. B-cells in the body produce antibodies that help to fight against the invading microbes. The adaptive immune response generated against the pathogen takes days or weeks to develop but may be long-lasting like tetnus, or even lifelong like chiken pox 2. ARTIFICIALLY ACQUIRED ACTIVE IMMUNITY- It is protection produced by intentional exposure of a person to antigens in a vaccine, so as to produce an active and lasting immune response. The antigens in the vaccine stimulate the immune system to produce antibodies and memory cells which are specifically directed against the antigens in the vaccine. After the immunization, if the living infectious agents with the same antigens that were in the vaccine get into the person’s body, the correct antibodies are already present and they bind to the infectious agents. The memory cells generate a rapid immune response from the rest of the immune system, and the infectious agents are quickly attacked and destroyed, often before symptoms of the disease can develop. ACTIVE IMMUNITY
- 11. ACQUIRED IMMUNITY ACQUIRED PASSIVE IMMUNITY Passive immunity refers to the process of providing IgG antibodies to protect against infection; it gives immediate, but short-lived protection—several weeks to 3 or 4 months at most. TYPES OF ACQUIRED PASSIVE IMMUNITY 1. NATURALLY ACQUIRED PASSIVE IMMUNITY -Maternal passive immunity is a type of naturally acquired passive immunity, and refers to antibody-mediated immunity conveyed to a fetus or infant by its mother. Naturally acquired passive immunity can be provided during pregnancy, and through breastfeeding. In humans, maternal antibodies (MatAb) are passed through the placenta to the fetus by an FcRn receptor on placental cells. 2. ARTIFICIALLY ACQUIRED PASSIVE IMMUNITY- Artificial immunity is a mean by which the body is given immunity to a disease by intentional exposure to small quantities of it. The most common form of artificial immunity is classified as active and comes in the form of antibiotics or lab made immunity, typically given to children and young adults.The passive form of artificial immunity involves introducing an antibody into the system once a person has already been infected with a disease, ultimately relieving the present symptoms of the sickness and preventing re- occurrence.Once the body has successfully rid itself of a disease caused by a certain pathogen, a second infection with the same pathogen would prove harmless. PASSIVE IMMUNITY
- 12. ACQUIRED IMMUNITY HUMORAL IMMUNITY • Humoral or antibody mediated immunity (AMI) is characterized by the production of antigen specific immunoglobulin molecules, called as ‘antibodies’, induced in response to an antigen and is mediated by B lymphocytes. Antibodies primarily defend against extracellular pathogens and toxins. Humoral immunity is so named because it involves substances found in the humors, or body fluids. • Humoral immunity is also called antibody-mediated immunity. With assistance from helper T cells, B cells will differentiate into plasma B cells that can produce antibodies against a specific antigen. The humoral immune system deals with antigens from pathogens that are freely circulating, or outside the infected cells . Whenever naïve B cells encounter an antigen in the lymphatic system, they undergo a differentiation process that leads to the creation of memory B cells and effector B cells. HUMORAL IMMUNITY
- 13. ACQUIRED IMMUNITY CELL MEDIATED IMMUNITY • Cell-mediated immunity (CMI) involves the activation of antigen-specific cells, such as CTLs and macrophages, which destroys the cells harboring antigen. Cellular immunity primarily defend against intracellular pathogens, multicellular parasites, transplanted tissue, and cancer cells. • Cell-mediated immunity does not depend on antibodies for its adaptive immune functions. Cell- mediated immunity is primarily driven by mature T cells, macrophages, and the release of cytokines in response to an antigen. • cell-mediated immunity, so named because the T cells themselves latch onto the antigens of the invader and then initiate reactions that lead to the destruction of the nonself matter. B lymphocytes, on the other hand, do not directly attack invaders. Rather, they produce antibodies, proteins that are capable of initiating reactions that weaken or destroy the foreign substance. CELL MEDIATED IMMUNITY