Immunology

Helpful Hints Don’t read your book during the courses, thinking is more immportant. Think, rather than memorize Understanding the concepts is not optional Test questions are based on concepts Ask questions Don’t wait until the last minute to study for the exam Check the website

What is immunity? Distinguishes “self” from “non-self” Danger Hypothesis “Protection” from infection, tumors, etc. A response that may result in host tissue damage

The Beginning of Immunology Edward Jenner discovered that cowpox vaccination protected against smallpox in 1796. Officially eradicated in 1979.

Two types of immunity Innate immunity (not antigen-specific) Anatomical barriers Mechanical Biochemical Non-specific (eg. Low pH in stomach) Receptor-driven (eg. PAMP-recognition) Adaptive immunity (antigen-specific) Receptor-driven Pre-existing clones programmed to make a specific immune response (humoral/cellular)

Antigen A substance (antigen) that is capable of reacting with the products of a specific immune response, e.g., antibody or specific sensitized T-lymphocytes. A “self” component may be considered an antigen even though one does not generally make immune responses against those components.

Characteristics of Adaptive Immunity Immune response is highly specific for the antigen that triggered it. Receptors on surface of immune cells have same specificity as the antibody/effector activity that will be generated Exposure to antigen creates an immunologic “memory.” Due to clonal expansion and creation of a large pool of cells committed to that antigen Subsequent exposure to the same antigen results in a rapid and vigorous response

What happens upon antigen exposure? B lymphocytes T lymphocytes Virgin lymphocyte pool PRIMARY RESPONSE effector cells memory cell pool SECONDARY RESPONSE Exposure to Antigen (Naturally-acquired or artificial) effector cells memory cell pool Activated T lymphocytes Plasma cells Regulatory Cytotoxic Antibodies

What are the effector functions? Antibody-Mediated Ways to Destroy the Target Complement activation Agglutination Neutralization Mask receptors Antibody-mediated cellular cytotoxicity (ADCC) Opsonization and phagocytosis Cell-Mediated Cytotoxic T-Lymphocyte Natural Killer Cells Antibody-mediated cellular cytotoxicity (ADCC)

B cells make antibodies CD8+ killer T cells kill infected host cells CD4+ helper T cells sustain responses CD8+ killer T cells kill infected host cells

The Adaptive Response is a “Two-Edged Sword” Protection Damage to the host (hypersensitivities) Allergies Cell and tissue damage due to autoimmunity

Hypersensitivity Reactions When a good response goes terribly wrong Hypersensitivity Reactions Reactions that are detrimental to the host Autoimmunity Atypical immune responses (allergies) Inability to eliminate a pathogen (granulomas) The tissues become a carrier for a hapten (poison ivy, nickel, penicillin Rejection of transplanted tissues

The products of the immune response may be used To diagnose disease To monitor disease progress As reagents in assays to detect and quantify other substances

Components of the immune system

THE IMMUNE SYSTEM The immune system is a bodywide network of cells and organs that has evolved to defend the body against attacks by "foreign" invaders  The proper targets of the immune defenses are infectious organisms – Bacteria such as these streptococci;  Fungi  Parasites, including these worm-like microbes that cause schistosomiasis  Viruses such as this herpes virus

Cells involved in immunity platelets eosinophil megakaryocyte T Lymphocyte Pluripotent hematopoietic stem cell neutrophil B Lymphocyte common lymphoid progenitor basophil common myeloid progenitor Study Guide Can you describe the major classes of cells involved in immunity? Which cells are considered mononuclear leukocytes? What is the relationship between the monocyte and the macrophage? What is the relationship between the B-cell and the plasma cell? plasma cell mast cell Natural Killer cell monocyte macrophage

Lymphocytes Lymphocytes are a class of white blood cells that bear variable cell surface receptors for antigens. There are two main classes of lymphocytes- B and T cells-which mediate humoral and cellular immunity respectively.

Polymorphonuclear leukocytes (or Granulocytes) Where is that stuff? Blood Serum or Plasma Leukocytes, Platelets and RBC Mononuclear Cells Polymorphonuclear leukocytes (or Granulocytes) Serum Proteins Immunoglobulins Complement Clotting factors Many others Lymphocytes (T cells, B cells & NK cells) Monocytes Neutrophils Eosinophils Basophils

Lymphoid Organs Primary or central lymphoid organs bone marrow and thymus where lymphocytes are generated Secondary or peripheral lymphoid organs where adaptive immune responses are initiated

Distribution of Lymphoid Tissues

Mucosal-associated lymphoid tissues (MALT) Will be discussed in the Spring Salivary Gland Course

What’s the bottom line? Innate immunity is a function of anatomical, mechanical and biochemical factors. No requirement for prior exposure/memory Biochemical response may involve pattern recognition Lacks the specificity of the adaptive immune system Adaptive immune system recognizes foreign agents via receptors and develops memory. Triggering the adaptive immune response results in activated T cells and antibodies specific for the substance (antigen) that triggered it. Antibodies react with antigen Block or neutralize Activate complement system Bind to Fc receptors on cells providing specificity to the effector activity of those cells Activated T cells Cytotoxic against foreign agent (tumor cell, transplant, virus-infected cell) May influence other cells (Helper/Suppressor T cells, cytokines)

Host Defense Defense Mechanisms Inborn independent of previous experience Innate after natural exposure to a foreign agent Active Defense Mechanisms Naturally acquired Passive placental transfer Adoptive immune cells in colostrum immune cells in colostrum Acquired Study Guide What is immunity? What distinguishes the various types of immunity? What is the difference between "innate" and "adaptive" immunity Active Specific immunization Artificially acquired Passive administration of preformed antibodies Adoptive Bone marrow transplant

Subsequent lectures Immunoglobulin structure Antibody/antigen reactions T cell-mediated immunity Humoral immunity Innate immunity Hypersensitivity reactions Autoimmunity Tumorimmunity