Faculty of Veterinary Medicine Universiti Malaysia Kelantan. Immunology and Serology (DVT2153)

Transcription

1 Faculty of Veterinary Medicine Universiti Malaysia Kelantan Immunology and Serology (DVT2153) By Dr. Erkihun Aklilu 1

2 Immune Response AgAinst Various infectious agents Immunology and Serology (DVT2153) Sem II (February 2013) Lecture II 2

3 Immune Responses 3 Fig. The time course of innate and adaptive immunity. Innate immunity provides the first line of defence and keeps pathogens at bay until the adaptive immunity is initiated.

4 Non-specific immune responses comprise the following principal elements: Anatomical/Mechanical/Physical barriers Secretory molecules Cellular components 4

5 I. Anatomic/Mechanical Barriers: Components: Skin and internal epithelial layers The movement of the intestines Mucous membranes lining the respiratory, digestive, reproductive and urinary tracts The oscillation of broncho-pulmonary cilia Fever 5

6 I. Anatomic/Mechanical Barriers: The protective actions of mechanical barriers are enhanced through biological factors and chemical factors 6

7 I. Anatomic/Mechanical Barriers The skin and epithelial surfaces Mechanical/physical barrier Act as first-line of defense Impermeable to most infectious agents Mechanism 7 Physical barrier Desquamation of skin: removes bacteria and other infectious agents

8 I. Anatomic/Mechanical Barriers Mechanism Ciliary movement and peristalsis: Keeps the respiratory tract and alimentary tracts respectively free from pathogens Tears and saliva: Flushing action prevents infection of the eyes and mouth Mucus lining: Has trapping effect (i.e. traps pathogens and dust particles ). The respiratory tract and GIT are lined with mucus 8

9 Chemical components: Sweat contains fatty acids that inhibit the growth of bacteria. Lysozyme and phospholipase found in tears, saliva and nasal secretions can breakdown the cell wall of bacteria and destabilize bacterial membranes. 9

10 Chemical components: The low ph of sweat and gastric secretions prevents growth of bacteria. Defensins found in the lung and gastrointestinal tract have antimicrobial activity. Surfactants in the lung act as opsonins 10

11 Biological components The normal flora of the skin and in the gastrointestinal tract Function: Prevent the colonization by pathogenic bacteria Secreting toxic substances Competing with pathogenic for nutrients or attachment to cell surfaces. 11

12 Humoral Immune Responses Once the physical barriers are breached, the humoral component of the innate immune response is activated. Humoral factors are found in serum or they are formed at the site of infection. 12

13 Humoral Immune Responses Characteristics and Mechanism: Acute inflammation which is characterized by edema and the involvement of phagocytic cells Humoral factors play an important role in inflammation 13

14 Components of Humoral immune Responses 1. Complement system The complement system is the major humoral non-specific defence mechanism Once activated complement can lead to increased vascular permeability, recruitment of phagocytic cells, and lysis and opsonization of bacteria. 14

15 2. Coagulation system May or may not be activated (depends on the severity of the tissue injury) Some products of the coagulation system can contribute to the non-specific defences 15

16 2. Coagulation system Some have the ability to increase vascular permeability and act as chemotactic agents for phagocytic cells. In addition, some of the products of the coagulation system are directly antimicrobial. (E.g. beta-lysin, a protein produced by platelets during coagulation can lyse many Gram positive bacteria by acting as a cationic detergent) 16

17 3. Lactoferrin and transferrin (proteins) Limit bacterial growth by binding iron ( an essential nutrient for bacteria) 4. Interferons (proteins) Limit virus replication in cells. 17

18 5. Lysozyme Breaks down the cell wall of bacteria. 6. Interleukin-1 ( Il-1) Induces fever and the production of acute phase proteins, some of which are antimicrobial since they can opsonize bacteria. 18

19 Physico-chemical barriers to infection 19

20 Humoral Immune Reponses Antigen? Any substance capable of inducing a specific immune response and of reacting with the products of that response, i.e., with specific antibody or specifically sensitized T lymphocytes, or both. (Medical Dictionary) 20

21 Humoral Immune Reponses Antigen? Any molecule or molecular fragment that can be bound by a major histocompatibility complex (MHC) and presented to a T-cell receptor Immunogen? Is a specific type of antigen 21

22 Humoral Immune Reponses Immunogenecity? Is the ability to induce a humoral and/or cell-mediated immune response Antigenicity? Is the ability to combine specifically with the final products of the immune responses (i.e. secreted antibodies and/or surface receptors on T-cells) 22

23 Humoral Immune Reponses Antigens are usually proteins or polysaccharides. Include : parts (coats, capsules, cell walls, flagella, fimbrae, and toxins) of bacteria, viruses and other microorganisms. Lipids and nucleic acids are antigenic only when combined with proteins and polysaccharides. 23

24 Humoral Immune Reponses Non-microbial exogenous (non-self) antigens can include pollen, egg white, and proteins from transplanted tissues and organs or on the surface of transfused blood cells. Vaccines are examples of immunogenic antigens intentionally administered to induce adaptive immunity in the recipient 24

25 Humoral Immune Reponses Animations/Videos of Antigen-Antibody Reaction 1. Videos and Animations\3D_Medical_Animation_Antibody_Immune_Response.mp4 2. Videos and Animations\Antigen_Processing_and_Prsentation.avi.mp4 25