IMMUNOLOGICAL DEFENSE MECHANISMS

Presented by: Miss Sefakor Agbenyegah

MPhil Biochemistry(4575215)

http://www.was-ist-antiaging.de

IMMUNOLOGY Study of biological mechanisms used by larger

organisms to protect themselves against invasion by other organisms

Immune – having a high degree of resistance to a particular disease or infection

Immune system – biological mechanism for identification and elimination of pathogens in a larger organism

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DEFENSE MECHANISMS Physical, chemical and biological properties of an

organism which reduce its susceptibility to foreign organisms/ materials

Three lines of defense – First, second and third lines

Generally classified under specific or non-specific

Non-specific mechanisms repel all microbes equally

Specific mechanisms are tailored for particular microbes

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LINES OF DEFENSE MECHANISMS01/05/2023

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FIRST LINE OF DEFENSE 01/05/2023

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FIRST LINE OF DEFENSE CONT’D Mechanical – cilia, mucous membranes,

Chemical – lysozyme, pH, lactate, defensins

Biological – normal flora,

Reflexes – vomiting, diarrhoea, coughing, sneezing,

SECOND LINE OF DEFENSE Cellular counterattack – when first line is evaded Involves two major classes of defenses:

Cellular defenses Molecular defenses

Cellular defenses: Inflammation Phagocytosis Natural killer cells activity Fever Blood clotting

Molecular defenses: Complement proteins Cytokines

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PHAGOCYTOSIS

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NATURAL KILLER CELLS Lymphocyte-like cells with granular cytoplasm Attack and phagocytize

Already invaded cells Cancer cells

FEVER: May be triggered in a large-scale infection

Role of fever: inhibits microbial multiplication by reducing

blood levels of iron speeds up body repair processes

High fevers may however be dangerous

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MOLECULAR DEFENSES Cytokines

Block viral replication using interferons trigger the inflammatory response elevation on the body temperature activate NK cells and macrophages

Complement proteins About 30 different inactive proteins that circulate in

the blood produced by the liver Involved in opsonization Attract phagocytes by chemotaxis Promote inflammation Punch holes in membrane of bacteria

THIRD LINE OF DEFENSE Made up of cells and chemicals which attack specific

antigens An antigen is a protein molecule that provokes

specific immune response in the body May be antibody-mediated (humoral immunity) or

cell-mediated Involves lymphocytes, macrophages and dendritic

cells Slow response; Exposure results in immunologic

memory by T and B lymphocytes

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REFERENCES Zabriskie, J. B., (2010). Essential clinical

immunology, Cambridge University Press, pp. 34-40; 111

Kim, Y. J., (2014). Autoimmunie diseases, A rising epidemic, Medicine, pp 15-20

Silverstein, A., (2001). Autoimmune diseases, Nat. Immunol. 2, 279-281.

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THANK YOU