Introduction to Immunology: Workbook

Introduction to Immunology Workbook

• This workbook complements immunology sessions.
• The initial session, "Introduction to Immunology," is self-directed.
• PowerPoint slides and instructions should be followed.
• External documents and research articles are available to expand knowledge.
• Varied note-taking methods like spider diagrams and tables are encouraged.
• Completion of the workbook and note consolidation is essential for session preparation.

Learning Objectives

Upon completion, students should be able to:

• Define immunology and understand its terminology.
• Describe the body's natural defense mechanisms.
• Identify components and functions of both non-specific (innate) and adaptive (acquired) immune systems.
• Differentiate between non-specific and adaptive immunity.
• Recognize and list cells of the non-specific and adaptive immune systems.

Key Terminology

• Immunology terminology should be reviewed and notated, adding new terms as encountered.

Microbe

• Microscopic organisms residing in water, soil, or air.
• Some microbes are pathogenic, while others are commensal and important for health.

Antigen

• Any substance capable of triggering an immune response
• Reacts specifically with the resulting antibodies or generated cells.

Cytokine

• A protein that modulates the immune system, either enhancing or suppressing it.
• They can be produced naturally in the body or in a laboratory.
• Examples include Interleukins, Lymphokines, Monokines, and Interferons (IFN).
• Type-1 Cytokines are produced by Th1 T-helper cells.
• Type-2 Cytokines are produced by Th2 T-helper cells.

Antibody (Immunoglobulin Ig)

• Specialized proteins produced by activated B cells that can neutralize or weaken infectious agents.
• Travel in the bloodstream to find specific pathogens.
• The body can create them in response to new pathogens or vaccines
• IgA (immunoglobulin A) has 2 forms, secretory and serum
  • Secretory IgA is found in the linings of the respiratory tract & digestive system, saliva, tears, and breast milk, known as the antiseptic paint of mucous membranes, and can activate the complement system in the presence of lysosome to kill certain organisms
  • Serum IgA can not activate the complement system
• IgD (immunoglobulin D) Found in blood in low levels and cannot activate the complement system. Approximately half of antigen specific receptors on B lymphocyte membranes are composed of IgD antibodies
• IgE (immunoglobulin E) Found in serum- small amounts, IgE is attached to mast cells & basophils (granulocytes). High levels of IgE found on those with allergies (e.g asthma/hayfever)
• IgG (immunoglobulinG) is the most common antibody in blood/tissue fluid- 75% of total serum immunoglobin level. Defends against diffusing toxins and spreading microbes, IgG response found mainly to occur in the secondary immune response. Effective opsonins. Maternal IgG is transferred across placenta, giving passive protection to new borns for 4-6/12)
• IgM (immunoglobulin M) is the largest of the immunoglobulin molecules, usually the earliest antibody response in a primary immune response, and short lived

Phagocyte

• Cells that engulf pathogens by attaching to and wrapping around them.
• The pathogen is trapped in a compartment called a phagosome.
• The phagosome merges with a lysosome to form a phagolysosome to be killed by toxic materials.
• Examples: Monocytes, macrophages, granulocytes, and dendritic cells.

Proteins

• Large molecules composed of amino acid chains.
• Chains are arranged in a specific order dictated by DNA.
• Examples: Antibodies, signaling proteins like cytokines, and complement proteins.

Opsonins

• Serum substances that enhance phagocytosis of bacteria
• Act as markers: IgG antibody and C3b molecule of the complement system.

Opsonize

• Refers to the ability of antibodies and complement components to coat dangerous antigens.
• Opsonins act as markers for recognition by the immune system.

Phagocytosis

• Process where cells called phagocytes ingest other cells or particles.
• Example: Neutrophil phagocytosing a bacterium.

Apoptosis

• A type of programmed cell death, used by the body to eliminate unneeded or abnormal cells.
• This process may be blocked in cancer cells.

Antigen Presenting Cell

• Cells that process protein antigens into peptides and present them to T-cell receptors.
• Examples: Macrophages, dendritic cells, and B cells.

Complement System

• Part of the innate immune response, crucial for host defense and inflammation.
• It has three pathways: Classical, Alternative and Lectin.

PMNs (Polymorphonuclear Leukocytes)

• A type of white blood cell with examples including neutrophils, eosinophils, basophils, and mast cells (granulocytes).
• Function to protect the body from infectious organisms as part of the innate immune system.

Cells of the Immune System: Macrophage

• Mononuclear leukocyte, exiting the bloodstream to become macrophages
• Kupffer cells in the liver and Histiocytes in connective tissue
• Largest of the WBC, performs phagocytosis and presents antigens to T cells.
• They recruit other phagocytic cells by releasing cytokines, initiating inflammation.
• Target old, damaged, and dead cells.

Cells of the Immune System: Neutrophils

• Granulocyte, myeloblast differentiate into, most common white blood cell
• Performs phagocytosis and degranulation (discharge of contents of a cell).
• Also releases burst of super oxides that have ability to kill many bacteria at same time
• Target bacteria and fungi

Cells of the Immune System: Eosinophils

• Granulocyte, myeloblast differentiate into, part of the innate immune system
• Degranulation and the release of enzymes, growth factor and cytokines
• Target parasites, and involved in various allergic reactions

Cells of the Immune System: Basophils

• Granulocyte, myeloblast differntiates into, part of the innate immune system
• Degranulation, release of histamine, enzymes and cytokines
• Target various allergic reactions, secrete anticoagulants (heparin) thus promoting mobility of other WBCs to prevent clotting, and secrete antibodies that have function

Cells of the Immune System: Mast Cells

• Granulocyte, derived from bone marrow myeloid stem cell
• Released into blood and only mature once recruited into tissue, located at boundaries between tissues and external environment
• Once activated, release a wide variety of inflammatory mediators (cytokines) from various antigens and mediators and host defense

Cells of the Immune System: Dendritic Cells

• Mononuclear Leukocytes derived from monocytes and found in nodes and in the spleen
• Links the innate and adaptive immune system- acting as messengers between the two and is the most potent type of antigen presenting cell
• Key regulator of the immune system, able to switch on cell surface receptors which activate immature T cells and stimulate growth and differentiation of of to kick start the adaptive immune response, also capture and process antigens

Cells of the Immune System: Lymphocytes T Cells

• Mononuclear leukocytes, lymphoblast, mature in the thymus, differentiate into antigen specific effector cells and either T helper cells or cytotoxic T cells.
• Triggers when a recirculating T Cell recognizes its specific antigen on the surface

Cells of the Immune System: Lymphocytes B Cells

• Mononuclear leukocytes, lymphoblast, mature in the bone marrow, differentiate with plasma cells and memory cells, is Adaptive and is a humoral/antibody mediated response
• Th cells target intracellular bacteria
• Cytotoxic T cells target virus infected and tumor cells
• Natural Killer cells attack virus infected and tumor cells, as well

Distinctions Between Innate and Acquired Immunity

• Innate immunity is non-specific, immediate (hours), non-antigen dependant and has no memory.
• Adaptive immunity is specific, takes days/weeks, antigen dependant, and has memory.

Barriers of the Innate Immune System

• Anatomic skin acts as initial mechanical barrier.
• The mucous membrane: normal flora compete with microbes for attachment sites
• Physiological temperature such as a fever response can inhibit pathogen proliferation

Barriers of the Innate Immune System 2

• Low pH, stomach releases hydrochloric acid to kill of undigested pathogens
• Chemical mediators - Lysozyme cleaves, Interferon induces antiviral defenses, Complement lyses Phagocytic (internalise) - macrophages, dendritic cells, and neutrophils
• inflammatory - recruitment of blood leukocytes, release of cytokines and histamine