Immunology is a broad branch of biomedical science

Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. l It deals with l l The physiological functioning of the immune system in states of both health and disease l Malfunctions of the immune system in immunological disorders (autoimmune diseases, hypersensitivities, immune deficiency, transplant rejection) l The physical, chemical and physiological characteristics of the components of the immune system.

Immune system An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. l It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own healthy cells and tissues in order to function properly. l Immune system composed of: l ¡ Bone marrow, spleen, lymphatic system and thymus

Innate Immunity l The innate immune system comprises the cells and mechanisms that defend the host from infection by other organisms, in a non-specific manner. l Innate immune systems provide immediate defense against infection, and are found in all classes of plant and animal life. l Everyone is born with innate (or natural) immunity, a type of general protection that humans have.

l Innate immunity includes Anatomical barriers to infections 1. Mechanical factors eg. the epithelial surfaces give a protection for body organs 2. Chemical factors eg. fatty acids in sweat inhibit the growth of bacteria. 3. Biological factors The normal flora of the skin and in the gastrointestinal tract can prevent the colonization of pathogenic bacteria by secreting toxic substances for pathogenic bacteria l Humoral barriers to infection eg. Complement system, coagulation system, interferons, lysozyme l Cellular barriers to infection Neutrophils, macrophages, eosinophils

Adaptive (active) Immunity l This type of immunity develops throughout our lives. l Adaptive (active) immunity involves the lymphocytes and develops as children and adults are exposed to diseases or immunized against diseases through vaccination.

Passive Immunity l Passive immunity is "borrowed" from another source and it lasts for a short time. l For example, antibodies in a mother's breast milk provide an infant with temporary immunity to diseases that the mother has been exposed to. This can help protect the infant against infection during the early years of childhood.

Antibodies (immunoglobulins) l Antibodies are gamma globulin proteins that are found in blood or other bodily fluids of vertebrates , and are used by the immune system to identify and neutralize foreign objects, such as bacteria and viruses. l Antibodies are produced by a kind of white blood cell called a plasma cell. l There are five different antibody isotypes are known in mammals (Ig. M, Ig. G, Ig. A, Ig. E, Ig. D) l These isotypes are perform different roles, and help direct the appropriate immune response for each different type of foreign object they encounter.

Antigen and immunogen l An antigen is a molecule recognized by the immune system. Originally the term came from antibody generator and was a molecule that binds specifically to an antibody l Self antigens are usually tolerated by the immune system; whereas "Non -self" antigens are identified as intruders and attacked by the immune system. l Immunogen is a specific type of antigen. An immunogen is defined as a substance that is able to provoke an adaptive immune response if injected on its own l Said another way, an immunogen is able to induce an immune response, while an antigen is able to combine with the products of an immune response once they are made.

Pathogen l A pathogen) , from Greek πάθος pathos "suffering, passion", and γἰγνομαι (γεν-) gignomai (gen-) "I give birt to") l An infectious agent , or more commonly germ , is a biological agent that causes disease to its host l Pathogen may be bacteria, virus, fungi, parasite, protozoa, parasite, tumor cells or self proteins.

complement system l The complement system is a biochemical cascade that helps, or “complements”, the ability of antibodies to clear pathogens from an organism. l The complement system consists of a number of small proteins found in the blood, generally synthesized by the liver , and normally circulating as inactive precursors( pro -proteins) l Stimulation of these proteins result in the activation of the cell-killing membrane attack complex.

Inflammation Latin , inflammare , to set on fire l Is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens , damaged cells, or irritants l It is characterized by ¡ increased blood flow to the tissue causing ¡ increased temperature, ¡ redness, ¡ swelling, and ¡ pain. l Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process. .

Histamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter l Histamine triggers the inflammatory response. l As part of an immune response to foreign pathogens , histamine is produced by basophils and by mast cells found in nearby connective tissues. l Histamine increases the permeability of the capillaries to white blood cells and other proteins, in order to allow them to engage foreign invaders in the infected tissues l

Allergy l Is a hypersensitive disorder of the immune system. Allergic reactions occur to normally harmless environmental substances known as allergens ; these reactions are acquired , predictable, and rapid. l Allergy is one of four forms of hypersensitivity. l It is characterized by excessive activation of certain white blood cells called mast cells and basophils by a type of antibody known as Ig. E , resulting in an extreme inflammatory response. l Common allergic reactions include eczema , hives , hay fever , asthma attacks , food allergies , and reactions to the venom of stinging insects such as wasps and bees. l

Autoimmunity l Is the failure of an organism to recognize its own constituent parts as self , which allows an immune response against its own cells and tissues. l Any disease that results from such an aberrant immune response is termed an autoimmune disease. l Prominent examples include ¡ ¡ Systemic lupus erythematosus) SLE Rheumatoid arthritis) RA

Transplant rejection l Transplant rejection occurs when a transplanted organ or tissue is not accepted by the body of the transplant recipient. l This is explained by the concept that the immune system of the recipient attacks the transplanted organ or tissue. l This is expected to happen, because the immune system's purpose is to distinguish foreign material within the body and attempt to destroy it, just as it attempts to destroy infecting organisms such as bacteria and viruses l When possible, transplant rejection can be reduced through the use of immunosuppressant drugs

Diagnostic immunology l The specificity of the bond between antibody and antigen has made it an excellent tool in the detection of substances in a variety of diagnostic techniques. l Antibodies specific for a desired antigen can be conjugated with a radiolabel, fluorescent label, or color-forming enzyme and are used as a "probe" to detect it.