Immunology Lecture 1 Flashcards
Cells of the immune system travel through…
The circulatory(blood) and lymphatic system(lymph)
True/False: Immune system protects the body at all times?
True
Immune system protects from…
Pathogens: Bacteria, viruses and parasites
Altered body cells: Cancer
Ture/False: Immune system reaches everywhere?
True
What are the two prongs of the immune system?
Non-specific/Innate
Specific/Adaptive
Are you born with both systems of the immune system?
Yes
Of the two prongs of the immune system which is the first-line of defence?
The non-specific/innate branch
Which prong of the immune system recognizes pathogens?
Specific/Adaptive immunity
What happens when the non-specific branch sees a pathogen for the second time?
Nothing! It has the same response each time it sees a pathogen no matter what kind of pathogen it is
What is a leap of faith?
Type of dicovery where we make an observation than take it a step further by testing a hypothesis
How was small pox a leap of faith?
Edward jenner noticed milk maids didnt contract small pox but had pock marks on their hands. The milk maids were contracting cow pox which was making them immune to small pox. He took a leap of faith by injecting pus from a cow pox lesion under the skin of a healthy individual. This prevented the person from getting small pox
What is serendipity?
Type of discovery
“Happy Accident”: when something goes wrong, we look into greater detail and maybe find a new discovery
What was discovered via serendipity?
Penicillin
Examples of accident of nature?
HIV
SCIDS
What SCIDS?
Patients do not have a functional immune system
What is HIV?
HIV is due to a loss of the T helper cells, this prevents activation of B cells and T cells preventing the activation of an adaptive immune response
What three components make up the immune system?
- Lymphoid organs
- Immune cells
- Secretions of immune cells
What occurs at the primary lymphoid organs?
Stem cells divide and immune cells develop
What type of organs make up the primary lymphoid organs?
- Bone Marrow(prior to birth this yolk sac, fetal liver and fetal spleen)
- Thymus
What happens in the bone marrow?
-All blood cells are produced here(B cells and T cells)
-B cells mature here
What happens in the thymus?
-T cells mature here (travel to the thymus after being birthed in the bone marrow)
-Above the heart
- Contains phagocytic cells(dendritic, macrophages)
-Atrophies (old age thymus almost gone)
What occurs in the secondary lymphoid organs?
Immune response occurs here between pathogens and immune cells
What organs make up the secondary lymphoid organs?
- Lymph nodes
- Spleen
- Lymphoid Nodules
What is the role of the lymph nodes?
- Filter microbes
Macrophages in nodes phagocytixe microbes that enter lymph
What is the role of the spleen?
-Largest organs
-Removes/filters microbes and old erythrocytes with phagocytic cells
What makes up the lymphoid nodules?
- Tonsils
-MALT(Mucosal-Associated Lymphoid Tissues)
-Peyer’s Patch
-Appendix
How do immune cells travel through the body?
In the blood and lymph
Is the capillary more permeable to bacteria than the lymphatic system?
NO! The lymphatic system os more permeable just as it is with proteins
What type of cells are immune cells?
Leukocytes/White blood cells(lack hemoglobin)
Are all immune cells derived from the same cell?
Yes, they are all derived from the pluripotent hematopoietic stem cell in the bine marrow
What cells are porduced via the lymphoid lineage?
Lymphocytes that becomes T cells, B cells and NK cells
What type of T cells exist and what protein do they carry on their surface?
- T helper cells have CD4+
- Cytotoxic T-cells have CD8+
- Regulatory T-Cells have CD4+
What are the granulocyte immune cells?
- Eosinophils - destroy parasites
- Basophils - Release histamines and prostaglandins
- Mast Cells - Release histamines
What is the most numerous white blood cell?
Neutrophils - phagocytes
What do monocytes become?
Macrophages
Dendritic Cells
What is the first-line of defense in the non-specific branch of the immune system?
Physical barriers
What is the second-line of defense in the non-specific branch of the immune system?
Cellular factors
Humoral factors
What is the role of the first-line of defense barriers?
Keep pathogens from reaching our tissue & creating an unpleasant environment that discourages growth
Name some of the physical and mechanical
barriers
- Tight junctions in epithelia (separates apical and basal fluids)
- Mucus(hard for bacteria to move)
- Hair and Cilia
- Skin (water resistant, prevents entry of foreign substances)
Name chemical and microbiological barriers?
Enhance the barriers
1. Secretions: Sebum(low pH), Lysozymes(breaksdown bacterial cell walls) and gastric juice(low pH)
2. Normal flora (protects from bacteria overgrowth)
What happens when the first-line of defense in the non-specific branch is breeched?
The second line of defense in the non-specific will be used
What makes up the humoral factors of the second line of defense?
- Inflammation
- Antimicrobial Substances
- Interferons
What are the 4 signs of inflammation?
- Redness (increse blood flow)
- Heat (increased blood flow)
- Pain (tissue damage/ factors released)
- Swelling (fluid moves into tissue)
What are the 3 stages of inflammation?
- Vasodilation
- Emigration of phagocytes
- Tissue repair
What is vasodilation
widening of blood vessels allows more blood to flow to the site of injust also results in increased permeability of capillaries which allows substance to go to the damaged site
What humoral substances are produced?
- Interferons
- Complement
- Iron-binding proteins
How do viruses replicate?
Viruses move into a cells inject themselves into the cell and then generate copies of themselves. This then leads to the cell bursting and new viral particles infecting other cells
What does type I interferon do ?
Prevents viral replication
How does type I interferon work?
- Infected cell with the virus starts to produce type I interferons in response to being infected
2 . All cells have type I interferon receptors on their surfaces. Uninfected cells will recieve the type I interferon signal - This signal tells cells to produce antiviral proteins
- Now if the cell becomes infected with the viral particle it will be able to prevent its replication
What is complement?
Family of plasma proteins of 30 proteins that participate in the cascades C3b
How does C3b work?
It will move out into the tissue where bacteria are present, it then binds to the surface of the bacteria. Phagocytes have C3b receptors, they will then bind to the C3b and then easily engulf the molecule
What is opsonization?
Prepares the pathogen for eating
What do iron-binding substances do ?
When we have a bacterial infection the body responds by releasing more transferrin which will bind to any available iron and sequester it from bacteria that need it to divide
What are the cellular factors?
- Natural killer cells
- Phagocytic cells (neutrophils, macrophages, dendritic)
- Cells with inflammatory mediators (granulocytes)
How are NK cells similar to cytotoxic T cells and different ?
Similar:
- Attack/kill cells directly after binding
Different:
- NK cells are NOT antigen specifc
How do NK cells kill infected cells?
They release perforin (makes a pore in cell membrane) and granzymes (go through the pores into the cell)
Which cells express MHC-1 on their surface?
Nucleated body cells
Do RBCs express MHC-1?
No because they are not nucleated
How do NK cells recognize infected cells?
If NK cell binds to MHC-1 it will recieve a negative signal and will not bind NK activating ligand to kill cell
If NK does not bind to MHC-1, NK activating ligand will bind and cause the release of granzymes/perforin
Types of phagocytes?
Fixed-tissue macrophages -already in tissue
Neutrophils - recruited to site of injury
Monocytes - become macrophages and dendritic cells
What are the steps of phagocytosis?
- Adherence (microbe sticks)
- Ingestion (microbe put in a membrane bound compartment(phagosome))
- Digestion(phagosome fuses to lysosome that destroys bacteria)
- Killing (death of microbe)
How do phagocytes recognize microbes?
Microbes have PAMPs(pathogen assocaited molecular patterns) on their surface that are recognized by PRRs(Pattern recognition receptor) which are found on the surfaces of phagocytes
What is a Toll-Like Receptor?
A type of Pattern recognition receptor(PRR) found on the macrophage phagocyte
Describe the structure of a toll-like receptor?
- HAs an intracellular signaling domain
-Has an extracellular domain that recognizes PAMPs of pathogens
When do macrophages TLRs bind to pathogens PAMPs?
As so as the skin has been breeched and bacteria has entered the skin, macrophages bind to the PAMPs with their TLRs
What does the binding of PAMPs to TLRs do ?
Sneds a signal(cytokines) to tell the body there is an infection. These signals cause inflammation and recruitment of other types of phagocytes to fight the infection
In inflammation what is the emigration of phagocytes?
Phagocytes come are recruited to the site of injusry and help clean up bacteria