Immunology Flashcards
What is the role of the immune system? (2)
Protects the entire body, at all times:
- From Pathogens: Bacteria, Viruses, Parasites
- From altered body cells: Cancer
What is the difference between non-specific/innate and specific/adaptive immune systems?
Non-specific/innate is the first-line of defense and does not need to recognize the pathogen, while specific/adaptive requires recognition of the pathogen and has a faster response when it sees the same pathogen again.
What are the two branches of the immune system?
Non-specific/innate and specific/adaptive.
How does the immune system recognize something as “foreign”?
The immune system recognizes something as “foreign” through the recognition of antigens on the surface of the pathogen.
What are the ways discoveries in science have been made? (3)
- Accidents of nature
- Leaps of faith
- Serendipity
What are the 3 components of the immune system?
Lymphoid Organs
Immune Cells – Leukocytes
Secretions of Immune Cells
What are the two types of lymphoid organs and what is the difference ?
-Primary Lymphoid Organs
Sites where stem cells divide and immune cells develop
-Secondary Lymphoid Organs
Sites where most immune responses occur
What are the two primary Lymphoid Organs?
-Bone narrow (Yolk Sac and Fetal Liver in Embryo)
-Thymus
What is the role of Bone narrow (Yolk Sac and Fetal Liver in Embryo) as a primary Lymphoid Organ ? (2)
-B-cells and Immature T-cells are produced here
-Site Where B-Cells Mature
What is the role of Thymus as a primary Lymphoid Organ ? (2)
-Contains T cells, scattered dendritic cells, epithelial cells, and macrophages
-Site Where T cells mature
What happens to the thymus with age?
Atrophies
What are the Secondary Lymphoid Organs? (3)
Lymph nodes
Spleen
Lymphoid nodules
What is the role of Lymph Nodes? (2)
-Filter microbes
-Macrophages in nodes phagocytize microbes that enter lymph
What is the role of the spleen?
-Removes microbes and old erythrocytes
What are some of the Lymphoid nodules? (3)
-Tonsils
-Peyer’s Patches and MALT (Mucosal-Associated Lymphoid Tissues)
-Appendix
What is the largest lymphoid organ?
the spleen
What is the location of the thymus?
Above the heart.
What is the precursor of the WBCs?
Lymphoid stem cell : T cells, B cells, NK cells
Myeloid stem cell: Neutrophil, monocyte, eosinophil, basophil
What are the three types of T cells?
Cytotoxic T-Cells CD8+
Helper T-Cells CD4+
Regulatory T-Cells CD4+
What is the function of eosinophils? (2)
They ;
-destroy multicellular parasites
-and participate in immediate hypersensitivity reactions.
What is the function of basophils?
Release a variety of chemicals
histamine, prostaglandins
What is the function of Mast cells?
Release chemicals, histamine
What is the role of Neutrophils?
Phagocyte
What is the role of monocytes?
Become Macrophages and
Dendritc Cells (Phagocytes)
What is the function of dendritic cells?
Phagocytosis, antigen presentation
What is the function of NK cells?
Bind directly and nonspecifically to virus-infected cells and cancer cells and kill them
What is the function of cytotoxic T cells?
Bind to antigens on plasma membrane of target cells (virusinfected cells, cancer cells, and tissue transplants) and directly destroy the cells
What is the function of Helper T cells?
Secrete cytokines that help to activate B cells, cytotoxic T cells,
NK cells, and macrophages
What is the function of Plasma cells?
Secrete antibodies
What is the function of B cells?
Initiate antibody-mediated immune responses by binding specific antigens to the B cell’s plasma membrane receptors, which are immunoglobulins. Upon activation, are transformed into plasma cells, which secrete antibodies
Present antigen to helper T cells
What is Non-specific/Innate Immunity ?
Ability of the body to defend against microbes and other foreign substances - without recognition of the invading pathogen
What is the role of the First Line of Defense ?
Barriers to entry & creating an unpleasant environment for microorganisms
What are the barriers in the First Line of Defense? (6)
-skin
-Tight Junctions in Epithelia
-Mucus
-Hair and Cilia
-Secretions (Sebum, Lysozyme, Gastric Juice)
-Normal Flora
What are the two types of factors in the Second Line of Defense?
Humoral
Cellular
What are the Humoral Factors of the Second Line of Defense?
-Inflammation and Fever
- Antimicrobial Substances
-Interferons
What are the Cellular Factors of the Second Line of Defense?
-Phagocytic Cells
-Cells with inflammatory mediators
-Natural Killer Cells
What are the four distinct signs and symptoms of inflammation?
Redness, Heat, Pain, Swelling.
What are the three stages of inflammation?
- Vasodilation
- Emigration of Phagocytes
- Tissue Repair
What does vasodilation allow to do in the inflammatory response? (2)
*Widening of blood vessels allows more blood flow to the site
*Increased permeability of capillaries allows substances to go to the damaged site
What are the humoral substances that discourage microbial growth or spread of pathogens? (3)
Interferons (antiviral proteins)
Complement
Iron-Binding Proteins
What is the mechanism of action of Type I Interferon?
Prevent the virus from using the cell machinery to replicate itself
What is the Complement?
A large family of plasma proteins with multiple functions. 30 different proteins participate in the cascades.
Explain the complement, alternative pathway. (innate branch) leading to opsonization
The alternative pathway is going to lead to a complement protein called C3B, And C3B is going to be able to bind to the surface of the bacteria and via process called optionization, which is this kind of labeling.
So this complement protein is going to bind to the surface of the bacteria, which is going to make it more easily recognizable by phagocytic cells cells.
It will then be released and stick to the bacteria and that’s going to make it easier for the phagocytic cells to recognize these as foreign and ingest them all right.
What is the role of Iron-Binding Proteins in the immune system?
Iron-Binding Proteins, such as Transferrin, help to bind and transport iron, which is essential because iron is very important for bacterial infections. And so one of our nonspecific responses is going to try to sequester the iron. We want to keep the iron away from the infection, so making it harder for the bacteria to be able to divide without having enough iron.
What leukocytes are involved in the cellular factors in the second line of defense?
Natural Killer (NK) Cells
Phagocytes
How do NK cells differ from cytotoxic T cells?
NK cells are not antigen-specific, unlike cytotoxic T
cells.
How do NK cells recognize their target cells?
NK cells recognize cells not expressing MHC-I
What happens when NK cells encounter normal cells expressing MHC-I proteins?
NK cells do not kill normal cells expressing MHC-I proteins.
What happens when NK cells encounter cells with altered or absent MHC-I proteins?
NK cells are activated and release agents that kill
the cell. (perforin and granzyme)
What are phagocytes?
Phagocytes are cells that non-specifically engulf microbial invaders.
What are the types of phagocytes?
The types of phagocytes are fixed-tissue macrophages, neutrophils,
monocytes- (macrophages and dendritic cells)
What are the steps involved in phagocytosis?
Adherence, Ingestion, Digestion, Killing
Details: Endocytosis, Phagosome formation, Lysosome, Phagolysosome, Release of end products into or out of cell
How does a phagocyte recognize microbes?
It detects unique, conserved structures that are essential to microbial physiology, known as
molecular signatures of infection
What are Pathogen-Associated Molecular Patterns (PAMPs)?
Things our body does not express:
– Lipopolysaccharide (LPS) of gram-negative bacteria
– Peptidoglycan (PGN) of gram-positive bacteria
PAMPS are recognized by which immune system receptors?
Pattern Recognition Receptors (PRR), including Toll-Like Receptors on the surface of the macrophage
What are Toll-Like Receptors (TLRs)?
They are a family of highly conserved transmembrane receptors that are essential for
microbial recognition via PAMPs.
What are TLRs made up of? (2)
- Extracellular domain for recognition of pathogens
- Intracellular signaling domain
TLRs allow to start the process of ______ ?
inflammation
What are the three stages of inflammation?
- Vasodilation
- Emigration of Phagocytes
- Tissue Repair
What is chemotaxis?
It is the chemically stimulated movement of phagocytes.
What are chemokines/chemoattractants?
chemicals that attract phagocytes.
What is margination?
Margination is the sticking of phagocytes to endothelial cells.
What is diapedesis?
Diapedesis is the movement of phagocytes across the capillary wall.
What is the specific role of neutrophils in inflammation?
Neutrophils dominate the early stages of inflammation and die in the process of killing bacteria.