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By Leah Ricci.  There are two major kinds of defense that help an animal protect itself from dangerous viruses, bacteria, and other pathogens in food,

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Presentation on theme: "By Leah Ricci.  There are two major kinds of defense that help an animal protect itself from dangerous viruses, bacteria, and other pathogens in food,"— Presentation transcript:

1 By Leah Ricci

2  There are two major kinds of defense that help an animal protect itself from dangerous viruses, bacteria, and other pathogens in food, water, and air Overview:

3  The first is call INNATE IMMUNITY which is present before exposure to pathogens and is effective from the time of birth. › It is a kind of defense that is mediated by phagocytic cells, antimicrobial proteins, the inflammatory response and natural and killer cells

4  The second is ACQUIRED IMMUNITY which develops after exposure to inducing agents › Acquired defenses can distinguish one inducing agent from another by using lymphocytes (white blood cells)

5 This picture show about B lympocyte. the lympocyte is produce and mature in bone marrow. it job is very importance in producing antibodies to fight pathogen( the foreign substances that cause harm to our body)

6  Intact skin is a barrier that cannot normally be penetrated by viruses or bacteria but tiny abrasions may allow their passage  Mucous membranes lining digestive, respiratory and genitourinary tracts bar the entry of potentially harmful microbes › Mucous membrane also produces mucus which traps microbes and other particles

7  Secretions from the skin and mucous membranes also contain antimicrobial proteins › This protein is present in saliva, tears, and mucous secretions, lysozyme can destroy susceptible bacteria as they enter the upper respiratory tract of the openings around eyes

8  A bodies defenses depend mainly on PHAGOCYTOSIS, the ingestion of invading microorganisms by certain types of white blood cells generically referred to as phagocytes › these cells produce certain antimicrobial proteins and help initiate inflammation

9  Phagocytes attach to their prey via surface receptors that bind to structures found on many microorganisms but not on normal body cells › Microbes are destroyed by lysosomes in two ways  Nitric oxide and other toxic forms of oxygen contained in the lysosomes may poison the microbes.  Or, lysozyme and other enzymes degrade microbial components

10  Four types of white blood cells (leukocytes) are phagocytic › The most abundant are NEUTROPHILS which make up about 60%-70% of all white blood cells. Their life span is only a few days because they tend to self destruct during phagocytosis › MACROPHAGES(big eaters) are large long- lived cells that develop from monocytes, which make up %5 of white blood cells. Monocytes circulate in the blood for a few hours then transform into macrophages in the tissue

11 › EOSINOPHILS have low phagocytic activity but are critical to defense against multicellular parasitic invaders › DENDRITIC CELLS can ingest microbes like macrophages do but their main role is to stimulate the development of acquired immunity

12  Two types of INTERFERON ( and β) provide defense against viral infections  Other antimicrobial proteins include about 30 serum proteins that make up the COMPLEMENT SYSTEM › In absence of infection these proteins are inactive

13  Damage to the tissue can release numerous chemical signals that triggers a localized INFLAMMATORY RESPONSE  When injured, mast cells release their histamine, triggering dilation and increased permeability of nearby capillaries  Other cells send signals that promote blood flow causing redness and heat of inflammation  Blood clotting begins the repair process and blocks microbes to other parts of the body  Small proteins call CHEMOKINES direct the migration of phagocytes and signal them to increase production of microbe-killing compounds

14  NK cells patrol the body and attack virus- infected body cells and cancer cells › Once NK cells are attached to a virus- infected cell or cancer cell the NK cell releases chemicals that lead to the death of the stricken cell be APOPTOSIS or programmed cell death

15 Natural killer cells attacking a cancer cell NK Cancer Cell NK

16  The exoskeleton of insects, like the skin, and mucous membranes of vertebrates, provides an external barrier that can prevent entry of intruders  The insect equivalent to blood, the hemolymph, contains circulating cells called hemocytes

17  Recent research indicates that invertebrates lack cells analogous to lymphocytes the white blood cells responsible for acquired specific immunity in vertebrates  Invertebrates also have the ability to respond more quickly to a particular invader or foreign tissue the second time it is encountered


19  As macrophages and dendritic cells phagocytose microbes, the phagocytes begin to secrete CYTOKINES, proteins that help activate lymphocytes and other cells of the immune system › Any foreign molecule that is recognized by lymphocytes and elicits a response from them is called an ANTIGEN, large molecules either proteins or polysaccharides › A lymphocyte actually recognizes and binds to just a small accessible portion of an antigen called an EPITOPE

20 Cytokines

21  The vertebrate body is populated by two main types of lymphocytes: B lymphocytes (B cells) and T lymphocytes (T cells) › Both types circulate through the blood and lymph in the lymph nodes, and other lymphoid tissues

22  Each B CELL RECEPTOR for an antigen is a Y-shaped molecule consisting of four polypeptide chains: two identical HEAVY CHAINS and two identical LIGHT CHAINS › At the tips of the Y are light-and heavy-chain variable (V) regions the remainder is the constant (C) regions

23  Each T CELL RECEPTOR for an antigen consists of two different polypeptide chains ( and β) linked by a disulfide bridge  The receptors on the T cells recognize small fragments of antigens called MAJOR HISTOCOMPATIBILITY COMPLEX (MHC)  A new MHC molecule is transported toward the plasma membrane, binds with a fragment of protein antigen within the cells and brings it to the cell surface, a process called ANTIGEN PRESENTATION

24  Class II MHC MOLECULES are made by just a few cell types mainly dendritic cells, macrophages and B cells › Dendritic cells, macrophages and B cells are known as ANTIGEN-PRESENTING CELLS because of their key role in displaying such internalized antigens to another subgroup of T cells called helper T cells  CLASS I MHC MOLECULES, found on almost all nucleated cells of the body bind peptides derived from foreign antigens that have been synthesized within the cell › Class I MHC molecules displaying bound peptide antigens are recognized by a subgroup of T cells called CYTOTOXIC T CELLS

25 T cell pushing B cell on a background of collagen fibres in vitro

26  Lymphocytes that migrate from the bone marrow to the THYMUS, a gland in the thoracic cavity about the heart, develop into T cells  Lymphocytes that remain in the bone marrow and complete their maturation there become B cells

27 Lymphocyte Development

28  The selection of a B cell of T cell by an antigen activates the lymphocytes forming two clones of daughter cells › One clone consists of a large number of short lived EFFECTOR CELLS that combat the same antigen › The other clone consists of MEMORY CELLS, long lived cells bearing receptors specific for the same inducing antigen  This antigen-driven cloning of lymphocytes is called CLONAL SELECTION

29  PRIMARY IMMUNE RESPONSE, doesn't peak until about 10 to 17 days › During this time selected B cells generate antibody-secreting effector B cells call PLASMA CELLS and selected T cells are activated to their effector forms › If an individual is exposed again to the same antigen the response is faster, 2-7 days. This is called SECONDARY IMMUNE RESPONSE


31  The HUMORAL IMMUNE RESPONSE involves the activation and clonal selection of B cells resulting in production of secreted antibodies

32  The CELL MEDIATED IMMUNE RESPONSE involves the activation and clonal selection of cytotoxic T cells which directly destroy certain target cells  Central to this network of cellular interactions is the HELPER T CELL which responds to peptide antigens displayed on antigen-presenting cells and in turn stimulates the activation of nearby B cells and cytotoxic T cells

33  A surface protein called CD4, present on most helper T cells, binds the class II MHC molecule › This interaction helps keep the helper T cell and the antigen-presenting cell joined which activation of the helper T cell proceeds

34  Cytotoxic T cells eliminate body cells infected by viruses or other intracellular pathogens as well as cancer cells and transplanted cells  A surface protein called CD8, present on most cytotoxic T cells, greatly enhances the interaction between a target cell and a cytotoxic T cell › When a cytotoxic T cell is selected by binding to class I MHC molecule-antigen complexes n an infected body cell, the cytotoxic T cell is activated and differentiates into an active killer

35  Immunity conferred by natural exposure to an infectious agent is called ACTIVE IMMUNITY because it depends on the action of a persons own lymphocytes and the resulting memory cells specific for the invading pathogen › Active immunity also can develop following IMMUNIZATION, often called VACCINATION helping induce an immediate immune response and long-lasting immunological memory


37  A red blood cells have A antigen molecules on their surface, the A antigen may be recognized as foreign if placed in the body of another person  B antigen is found on type B; both A and B antigens are found on type AV; and neither antigen is found on type O red blood cells


39  Blood group antigens and related bacterial epitopes are polysaccharides which induce immune responses in which no memory cells are generated › As a result anti-blood group antibodies are always IgM (primary responses) instead of IgG (secondary responses) this helps in pregnancy because it IgM does not cross the placenta and causes harm to the fetus


41  Allergies are exaggerated (hypersensitive) responses to certain antigens called allergens › The most common allergies involve antibodies of the IgE class. › Some of these antibodies attach by their tails to mast cells present in connective tissues and later when the allergen again enter the body they attach to the antigen-binding sites of mast cell- associated IgE cross linking adjacent antibody molecules › This induces the mast cell to release histamines, a process called degranulation › an acute allergic response sometimes leads to ANAPHYLACTIC SHOCK, a whole-body, life threatening reaction that can occur within seconds of exposure to an allergen

42  In some individuals the immune system loses tolerance for self and turns against certain molecules of the body causing one of the many AUTOIMMUNE DISEASES › Some diseases like Lupus, rheumatoid arthritis, and insulin-dependent diabetes mellitus can cause damage to the joints, skin, or kidneys

43  The inability of the immune system to protect the body from pathogens or cancer cells that it should normally be able to defeat reflects some sort of deficiency in the system

44  This results from defects in the development of various immune system cells or defects in the production of specific proteins such as IgA antibodies or complement components  In severe combined immunodeficiency (SCID) both the humoral and cell mediated branches of acquired immunity fail to function › The long-term survival or people with this disease required a bone marrow transplant

45  Immune dysfunction that develops later in life can be caused by exposure to a number of agents  Acquired immunodeficiency's range from temporary states that may arise from physiological stress to the devastative AQUIRED IMMUNODEFICIENCY SYNDROME, or AIDS, which is caused by a virus

46 Campbell, Neil A., and Jane B. Reece. Biology. 7th ed. San Francisco: Pearson, Benjamin Cummings, Print. AP Edition. "Lecture 1 : Organization of the Immune System." Faculty of Medicine. 29 Jan Web. 22 Aug "NIDA - Publications - NIDA Notes - Vol. 21, No. 6 - Research Findings." National Institute on Drug Abuse - The Science of Drug Abuse and Addiction. Web. 22 Aug "Phagocytosis - Definition of Phagocytosis in the Medical Dictionary - by the Free Online Medical Dictionary, Thesaurus and Encyclopedia." Medical Dictionary. Web. 22 Aug

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