Introduction To Immunology Flashcards
What is immunology?
It’s the study of the immune system and protection from infection through multiple lines of defence
What is the malfunctioning of the immune system?
Autoimmune diseases (e.g. rheumatoid arthritis, multiple sclerosis, Crohn’s Disease, systemic lupus erythematosus)
Allergies: hypersensitivity reactions resulting from the immune system reacting against innocuous foreign substances
Cancer: failure of immune cells to destroy cancer cells
Non-immunologic diseases: metabolic, cardiovascular, and neurodegenerative diseases
What are the cellular components of the blood?
Red blood cells-oxygen transport
White blood ells- immune responses
What does white blood cells consist of?
Granulocytes (have granules in the cytoplasm)
1. Polymorphonuclear leukocytes
2. Eosinophils
3. Basophils
Agranulocytes (have no granules in the cytoplasm)
1. Monocytes
2. Small lymphocytes
What type of white blood cells are there?
Polymorphonuclear leukocytes (PMLs)
PMLs constitute 50-70% of the white blood cells in peripheral blood.
They ingest and destroy foreign protein and bacteria.
Eosinophils
Eosinophils comprise 2-5% of the circulating white blood cells.
They migrate to inflammatory sites and kill large pathogens that cannot be ingested by PMLs.
Basophils
Constitute <1% of circulating WBCs.
Major cells in skin allergic reactions.
Monocytes /macrophages
Largest WBCs, constituting 2-6% of the circulating cells.
They degrade foreign material during immune responses.
They produce reactive oxygen species (ROS) and pro-inflammatory cytokines.
Monocytes migrate into tissues (liver, brain, bone) to form macrophages.
Lymphocytes
Mainly involved in immune responses.
What is innate immunity?
Innate immunity is deployed if the body’s protective barriers (skin, respiratory, intestinal and urogenital) are breached
This response fights infections until an adaptive immune response is deployed against the microbe
During this response, immune cells and antimicrobial proteins are activated by bacterial molecules known as Pathogen-Associated Molecular Patterns (PAMPs).
An adaptive response begins 7 to 10 days after infection.
What is pathogen- associated molecular patterns?
PAMPs are molecules that are found in most pathogenic bacteria and some bacteria
Examples of these molecules are: -components of bacterial cell walls, single and double stranded nucleic acids and unmethylated DNA
During innate immune responses, PAMPS are detected by:
-receptors on white blood cells and tissues aka pattern recognition receptors
-acute phase proteins
-serum complement compoonents
Pathogen associated molecular patterns examples:
PAMP- Associated pathogen
1.)Peptidglycan- Gram positive bacteria
2.) Lipoplysaccharide - Gram negative bacteria
3.)Lipoteichoic acids- Gram positive bacteria
4.)Flagellin- Bacteria
5.) Double stranded ribonucleic acid (RNA)- Viruses
6.)Lipopeptides- Mycoplasma
7.)Unmethylated CpGDNA- Bacteria
Pattern recognition receptors?
Immune cells (phagocytic cells) contain receptors which recognise PAMPs pathogenic microbes known as Pattern recognition receptors
The most important PRR is Toll-like receptors, which are found on white blood cells and play a role in innate immunity
Activation of toll like receptors by PAMPs on pathogenic microbes results in
Phagocytosis
Reactive oxygen and nitrogen species which kill bacteria.
Production of cytokines (e.g. interleukins) from phagocytic cells, which cause movement of phagocytic cells and lymphocytes from the blood.
Toll like receptors on and example of a disease like sepsis:
The PAMP is: Bacterial lipopolysaccharide (LPS) which is also an endotoxin
LPS released from bacteria and reacts with TLR-4 receptors on the surface of white blood cells mainly macrophages
This results in intracellular events culminating in the release of pro-inflammatory cytokines (IL-1, IL-2, IL-6, IL-8, and TNFα).
These cytokines (especially TNFα) are involved in septic shock.
Tachycardia
Vasodilation
Hypovolaemia
Inadequate tissue perfusion
What is immunogen?
An immunogen is a <3000 MW protein which stimulates the immune system to produce a response.
What is an antigen?
An antigen is the part of the immunogen that reacts with immune effector cells or soluble antibodies.
What is an allergen?
An allergen is an immunogen which elicits the production of allergic antibody.
Types of antigens:
Exogenous antigens are immunogenic structures expressed on extracellular bacteria, fungi, viruses, and pollens which enter the body via the oral, respiratory, and parenteral routes.
Endogenous antigens are generated by cells infected by viruses, intracellular parasites, or tumour cells.
Haptens are small-molecular-weight compounds that evoke an immune response only when they are attached to carrier proteins.
The immune response to a hapten is directed at both the hapten and the carrier protein.
Drugs as happens:
Some drugs (including antibiotics) are small compounds with MW < 3000.
The active drug or its metabolites are sometimes haptens which bind to serum proteins to elicit either an antibody or a cellular response.
This can result in:
Skin eruptions
Asthma
Anaphylaxis
Autoimmune reactions
Approximately 2% of patients administered the antibiotic penicillin develop urticaria or angioedema.
