IMMUNOLOGY Chapter 1 Dr Capers IRSC History Discipline

IMMUNOLOGY Chapter 1 Dr. Capers IRSC

History Discipline of immunology grew out of observation that individuals who recovered from infectious diseases were protected from disease 15 th Century Chinese and Turks tried to prevent smallpox Dried crust from pustules were inhaled or inserted into small cuts 1718 Lady Montagu had that technique done in her children

History 1798 Edward Jenner Noticed that milkmaids that contracted cowpox were immune to smallpox Innoculated small boy with fluid from cowpox pustule He then intentionally infected the boy with smallpox – the child did not develop smallpox 1881 Louis Pasteur Vaccinated sheep with heat-attenuated anthrax Then infected sheep with virulent strain of anthrax – they did not develop anthrax

History 1883 Metchnikoff demonstrated that certain white blood cells were able to phagocytize microorganisms 1901 Von Behring and Kitasato Demonstrated that serum (noncellular component of blood) from animals immunized to diptheria could transfer that immunity to non-immunized animals

History 1977 Last known naturally acquired case of smallpox Is it still a threat? In industrialized nations, measles, mumps, whooping cough, tetanus, polio, and diptheria are extremely rare or nonexistent This is due to vaccines! Prevent death, paralysis, deafness, blindness, mental retardation

A Little Bit of History

Immune system evolved to protect multicellular organisms from pathogens Does this by 2 related activites Recognition and response

Couple of terms we need to be familiar with: Pathogen – something that causes disease Antigen – any foreign substance that binds specifically to an antibody or T cell receptor Immunogen – a substance capable of eliciting an immune response All immunogens are antigens but not all antigens are immunogens (i. e. haptens) Epitope – portion of the antigen that is recognized by an antibody or T cell receptor

2 Systems of Immunity Innate Immunity 1 st line of defense Molecular and cellular mechanisms deployed before an infection Distinguishes between self and pathogens but not specialized to distinguish small differences in the foreign particles Adaptive Immunity Develops in response to infection Adapts to recognize, eliminate, and remember pathogen

Innate Immunity Less specific 1 st line of defense Barriers that protect host Skin Acidity of stomach Lysozymes in fluids Phagocytic cells Antimicrobial peptides (interferons, complement) Temperature

Adaptive Immunity Highly specific Characteristic attributes Antigenic specificity Antibodies can distinguish between 2 proteins that differ in only 1 amino acid Diversity Immunologic memory Self-nonself recognition

Adaptive Immunity Effective Immune response involves 2 groups of cells Lymphocytes B cells T cells Antigen-presenting cells

Lymphocytes B cells Mature in bone marrow Antigen binding receptor – Antibody Glycoproteins

Antibodies Glycoproteins Structure 2 identical polypeptides – heavy chains 2 shorter identical polypeptides – light chains

Antibodies Antigen coated by antibody is eliminated in several ways Antibody can cross-link several antigens, making it easier to be ingested by phagocytic cells Activate complement system resulting in lysis of microorganism

Lymphocytes T cells Arise in bone marrow but mature in thymus 2 well define subpopulations of T cells T helper cells T cytotoxic cells

T cells recognize antigen presented in MHC molecule MHC = Major Histocompatibility Complex MHC Class I – found on all of our nucleated cells Cytotoxic T cells recognize this MHC Class II – found on antigen presenting cells (B cells, dendritic cell and macrophages) Helper T cells recognize this

T cells Cytokines secreted by TH cells can activate phagocytic cells TC cells can kill altered self-cells Cells infected by viruses Tumor cells

Antigen presenting cell associating with T cell

Initial encounter with antigen causes primary response Later contact with antigen will result in more rapid response – secondary response

Immune Dysfunction Allergies and Asthma Graft rejection Autoimmune Disease Immunodeficiency