Immunity Mrs. Dalia Kamal Eldien MSc in Microbiology Mrs. Dalia Kamal Eldien MSc in Microbiology Lecture NO: 14

Immunity  Immunity is the state of protection against infectious disease conferred either through an immune response generated by vaccination or previous infection or by other non-immunological factors.  Definition of immunity: Is the body’s defense against foreign material and/ or pathogenic microorganisms.

Immune system  The immune system is a network of cells, tissues, and organs that work together to defend the body against attacks by “foreign” invaders.(bacteria, viruses, parasites, and fungi)  Because the human body provides an ideal environment for many microbes, they try to break in.  It is the immune system’s job to keep them out or, to seek out and destroy them.

 The key to a healthy immune system is its remarkable ability to distinguish between the body’s own cells—self—and foreign cells—nonself.  Anything that can trigger this immune response is called an antigen.  An antigen can be a microbe such as a virus, or even a part of a microbe, tissues or cells from another person (except an identical twins)  Antibodies are a proteins produced by body against specific antigen, found in the serum and other body fluids, react specifically with the antigens that induced their formation

Question  How person be immunized ???

Immunity  A person may become immune to a specific disease in several ways. For some illnesses, such as measles and chickenpox, having the disease usually leads to lifelong immunity to it. Vaccination is another way to become immune to a disease. Both ways of gaining immunity, either from having an illness or from vaccination, are examples of active immunity.

Immunity  A different type of immunity, called passive immunity, results when a person is given someone else’s antibodies. When these antibodies are introduced into the person’s body, the “loaned” antibodies help prevent or fight certain infectious diseases.  The protection offered by passive immunization is short- lived, usually lasting only a few weeks or months.

Types of active immunity  Active immunity results when a person’s immune system works to produce antibodies, it have two types:-  Innate Immunity (Natural immunity or non-specific)  Adaptive Immunity (Acquired immune response or specific immune response)

Innate immunity  First line of defense  Innate immune responses are general defense reactions, they include:-  The body’s natural barriers to infection (skin& mucous membranes)  Phagocytosis  Complement  Inflammatory process  Actions of natural killer (NK) cells.

Phagocytosis  Phagocytic cells engulfing and kill the invading pathogens.  Many microorganisms produce chemical substances that attract phagocytes.  The phagocytic cells are neutrophil circulate in the blood and respond rapidly to infection (form ‘pus cells’).  And Macrophages circulate in the blood as monocytes and are present in tissues as fixed or free macrophages.

Phagocytosis

Inflammatory response  Inflammation is characterized by 4 cardinal signs or symptoms 1-Fever 2- Redness 3- Swelling, local accumulation of fluid 4- Pain

Complement  Complement: Consists of a set of proteins which participate in both non-specific and specific immune defense.  In nonspecific defense, complement can be activated by bacterial peptidoglycan and lipopolysaccharide  Some Gram negative bacteria are lyzed by complement binding to their surface.

Natural killer cells  Natural killer cells: These are lymphocytes destroy the cells. E.g. o Infected cells (virus) o Tumor or cancer cells o They have no immunological memory.

Adaptive immunity  The innate responses call the adaptive immune responses into play, and both work together to eliminate the pathogens  Adaptive immunity occur following contact with a ‘foreign’ antigen, e.g. invading pathogen or its products.  Are highly specific to the particular pathogen that induced them, and they provide long-lasting protection  Adaptive immune responses eliminate or destroy invading pathogens and any toxic molecules they produce.  Because these responses are destructive, it is important that they are directed only against foreign molecules and not against molecules of the host itself  Adaptive immunity have immunological memory

Adaptive immunity  Are carried out by white blood cells called lymphocytes (two types of lymphocytes, called B cells and T cells)  There are two broad classes of such responses—antibody responses and T-cell-mediated immune responses  In antibody responses, B cells are activated to secrete antibodies, which are proteins called immunoglobulins.  In cell mediate immune responses, T cells are activated

Immune system disorder  Disorders of the immune system include: a.Allergy and asthma - immune responses to substances that are usually not harmful b.Immune deficiency diseases - disorders in which the immune system is missing one or more of its parts c.Autoimmune diseases - the immune system can mistake self for nonself and launch an attack against the body’s own cells or tissues.

This is the last lecture in basic microbiology, I wish all of you luck and success