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.
What are NETs?
Neutrophil Extracellular Traps are made of processed chromatin bound to granular and selected cytoplasmic proteins which come from the lysed neutrophils.
Produces pus.
What is pus?
a mixture of dead bacteria and neutrophils
What are the 3 types of Antigen?
- Immunogen – material that induces an immune response
- Allergen
- Ligand
What is an epitope?
An epitope is the part of the antigen that is recognized by the immune cells.
What is the role of the lymphatic system/lymph nodes in the activation of the adaptive response?
the lymphatic system is very permeable and so they can pick up these dendritic cells which are then going to travel to the regional lymph node where all these other immune cells are waiting to start the adaptive immune response.
Who is going to bridge the gap between the adaptive or between the adaptive immunity and the nonspecific immunity ?
dendritic cell
What are the two types of adaptive immunity?
Humoral - Antibody-Mediated Immunity
Cell-Mediated Immunity
What is the difference between humoral and cell-mediated immunity?
Humoral immunity involves B cells that transform into plasma cells and synthesize and secrete antibodies, while cell-mediated immunity involves cytotoxic T cells that kill infected body cells, cancer cells, and foreign cells.
What is the 2 classes of major histocompatibility complex
(MHC) and What is the difference between them?
MHC-I and MHC-II
MHC-I is expressed on all nucleated cells, while MHC-II is expressed only on antigen-presenting cells such as macrophages, dendritic cells, and B cells.
What is the process of antigen presentation by APCs? (5)
- Ingest antigen
- Digestion into peptide fragments
- Synthesize and package MHC-II molecules
- Bind peptide fragments to MHC-II
- Insert antigen–MHC-II complexes on plasma membrane
What are the 2 characteristics of antigens?
Antigens have :
-reactivity (meaning antibodies bind specifically to the antigen that provoked it)
-immunogenicity (meaning they can provoke an immune response
What cells are involved in specific/adaptive immunity?
B Cells and T Cells.
What are the three stages of a typical adaptive immune response?
-Recognition of an antigen by lymphocytes
-Lymphocyte activation
-Attack launched by the activated lymphocytes and their secretions
What are the origins of B cells and T cells? (precursors)
B cells and T cells originate from multipotent uncommitted hematopoietic stem cells, which differentiate into lymphoid stem cells.
What is the process of B cell activation?
B cells are activated by antigens, which cause them to transform into plasma cells that produce and secrete antibodies and memory cells.
What is the role of cytokines in the immune response?
Cytokines are signaling molecules that help regulate the immune response by activating and directing immune cells.
Th cells secrete cytokines to activate the B cells and the Tc cells.
What is the difference between CD4+ and CD8+ T cells?
CD4+ T cells are helper T cells that activate other immune cells, while CD8+ T cells are cytotoxic T
cells.
What is the process of Thcell activation?
The Th cells receives two signals from the ACP: MCH-II and B7 (binding to CD-28), allowing it to activate.
How do activated Tc cells attack cells?
directly attack antigen bearing cells
How do antibodies attack cells?
Guide phagocytes, complement and NK cells to attack antigen-bearing cells or to neutralize free
antigen
How is T cell activation regulated?
This involves displacement of CD28 from B7 by CTLA4 or PD-1.
What are the events Required for the Activation of Helper T Cells ? (3)
- Specific Recognition
MHC-II + Peptide – T Cell Receptor - Co-reception
CD28 – B7 - Cytokine Release from APC
Stimulates TH Cell
Where are the B cells activated?
Lymph nodes/secondary lymphoid organs :
spleen, lymphoid nodule, or lymph node
What plasma protein’s presence is spiked during infection?
gamma globulin
What is the structure of antibodies?
Two identical heavy chains
two identical light chains
What is the variable region in antibodies?
Antigen binding site
(FAB region)
What is the constant region in antibodies?
Same in all antibodies of a class
(FC region)
What are the 5 classes of antibodies?
IgG
IgA
IgM
IgD
IgE
What antibody am I? Found in MALT, breast milk
IgA
What antibody am I? first formed, lead to complement activation
IgM
What antibody am I? found in prenatal
IgD
What antibody am I? most numerous, crosses the placenta
IgG
What antibody am I? involved in allergies
IgE
What do B cells produce during clonal selection?
-plasma cells, which secrete specific antibodies,
-memory cells, which allow for a faster response if the antigen is seen again.
What is the difference between active and passive immunity?
Active immunity involves the person’s own immune system responding to a microbe, while passive immunity involves the person receiving antibodies from another person or animal and it’s temporary protection.
What type of immunity am I? Developing immunity to the flu virus after being exposed to it by chance.
Active natural
What type of immunity am I? Developing immunity to the flu virus after receiving a flu vaccine.
Active artificial
What type of immunity am I? A fetus receiving IgG antibodies from its mother across the placenta or a baby receiving IgA antibodies in breast milk.
Passive natural
What type of immunity am I?
Receiving serum containing antibodies from a person or animal that has been vaccinated.
Passive artificial
What is the general principle behind vaccines?
Exposure to the antigenic substance results in an active immune response that induces formation of memory cells.
What are the functions of antibodies? (7)
Neutralizing Antigen
Agglutination of Antigens
Precipitation of Antigens
Activating Complement
Opsonization
Antibody-Dependent Cellular cytotoxicity
Explain the Neutralizing Antigen function of antibodies.
Bacteria when replicating can release toxins. Antibody binds to toxins and it’s not going to be effective (effect of molecule based on 3D shape)– it’s now neutralized.
Explain the Agglutination of Antigens function of antibodies.
Agglutinate the antigen: gluing these microbes is going to prevent them from being able to travel further in the body and making them easier to phagocytose.
Explain the Precipitation of Antigens function of antibodies.
Can bring things out of solution (blood or fluid) and hold them together which can also facilitate phagocytosis.
Explain the Activating Complement function of antibodies.
Antigen-antibody complex will lead to activation of complement C1, which will set off a cascade of activity that will lead to activation of other complement family proteins to eventually produce membrane attack complex (MAC). (through the classical pathway).
How does MAC kill cells?
by generating pores on the cell membranes that will lead to loss of content which will lead to death of the cell
Explain the opsonization function of antibodies.
Uses opsonins to tag foreign pathogens by making them more visible for elimination by phagocytes. (phagocytes have receptors for the Fc region of antibodies)
Explain the Antibody-Dependent Cellular cytotoxicity function of antibodies.
process by which antibodies coat a target cell and recruit cytotoxic T cells to induce target cell death
Why is the rate of antibody production following initial exposure so slow?
Initially no receptors for that specific antigen- body needs time to first recognize the antigen and to clone the activated lymphocytes
Why is the rate of antibody production for a subsequent exposure to the same antigen much faster?
Thanks to the memory cells.
When memory B cells reencounter their specific antigen, they proliferate and differentiate into plasma cells, which then respond to and clear the antigen.
what is the role of RAGs?
The primary role of RAG proteins (RAG-1 and RAG-2) is to recognize specific DNA sequences, create double-strand breaks, and facilitate the random recombination of gene segments in the V(D)J recombination process, leading to the diversity of antigen receptor molecules in B cells and T cells.
what is the role of VDJ recombination?
The role of V(D)J recombination is to generate diversity in the antigen receptor genes of B cells and T cells, allowing them to recognize a wide range of antigens, including those from pathogens.
what is the role of TdT ?
The role of Terminal deoxynucleotidyl transferase (TdT) is to add random nucleotides to the junctions between V, D, and J gene segments during V(D)J recombination, increasing the diversity of antigen receptor sequences in B and T cells.
what is the difference between Pro-B cell, Pre-B cell, B cell, Plasma cell?
-Pro-B cell: In the early stage, undergoes heavy chain gene rearrangement.
-Pre-B cell: Expresses heavy chains and begins light chain gene rearrangement.
-B cell: Expresses both heavy chains and light chains, with a mature B cell receptor on the surface.
-Plasma cell: Differentiated B cell specialized in antibody production, secreting large amounts of antibodies.
What does the VDJ and C stand for?
variable
diversity
joining
constant
Which antibodies are produces first and which are produces right after? and why
IgM are produced first because they are the best for activating the complement but not eefficient for moving in the body because of it’s size . Then, IgG are peoduced, because they move way faster in the body due to their small size.
Under what circumstances will the body NOT create antibodies to self antigens?
Under normal circumstances.
How does immune tolerance develop during fetal
and early postnatal life?
Through clonal deletion or clonal inactivation of cells that match body antigens.
Where does the development of T cell tolerance occur?
In utero, in the thymus.
What must T cells recognize in order to survive negative selection?
MHC Class II molecules
What happens to T cells that recognize self-proteins or cells expressing MHC Class-I?
They will be negatively selected (destroyed).
What percentage of T cells produced will be
destroyed?
95%.
If we have the adaptative response, why do we still manage to get sick?
if the virus/bacteria can divide more rapidly than we can produce antibodies to fight infections, this can lead to experiencing illness.
What is the difference between endogenous and exogenous antigens?
Endogenous antigens are produced by body cells, while exogenous antigens come from outside the body.
What is the process of antigen presentation in endogenous antigen/infected body cells?
-Synthesis of MHC-I molecules
-Binding of peptide fragments to MHC-I molecules.
-Packaging of antigen–MHC-I complexes
-Insertion of antigen–MHC-I complexes into the plasma membrane.
What is the process of antigen presentation in exogenous antigens/antigen presenting cells?
-Synthesis of MHC-II molecules
-Binding of peptide fragments to MHC-II molecules.
-Packaging of antigen–MHC-II complexes
-Insertion of antigen–MHC-II complexes into the plasma membrane.
What is the molecule by which cells present antigens to cytotoxic cells?
with MHC-I.
What is the mechanism by which cytotoxic T cells
kill virus-infected cells?
release of granzyme and perforin
What are some factors that can alter resistance to infection? (5)
-Protein–calorie malnutrition
-Preexisting disease
-Stress and state of mind
-Sleep deprivation
-Modest exercise and physical conditioning
What are immunodeficiency diseases?
result from weak, underactive, or impaired immune systems.
What is SCID?
SCID is a group of related diseases that arise from an absence of both B and T cells and, in some cases, NK cells.
What is AIDS?
AIDS is a syndrome that infects and kills cells of the immune system. (and it’s central for activation of B cells and Tc cells)
What are some harmful immune responses? (5)
-Tissue/Graft Rejection
-Transfusion Reactions
-Allergy (Hypersensitivity)
-Autoimmune Disease
-Excessive Inflammatory Responses
Why can there be a problem during tissue grafts and organ transplantation?
MHC-I proteins on the graft cells and MHC-II proteins on the macrophages differ from the recipient.
The recipient’s T cells recognize these MHC proteins as foreign
The recipient’s cytotoxic T cells with the aid of helper T cells kill cells bearing the foreign MHCs.
How can we avoid rejection during tissue grafts and organ transplantation?
-Radiation to eliminated dividing cells
-Drugs that kill actively dividing lymphocytes
-Cyclosporine blocks cytokine production from helper T cells
What is the key factor in transfusion reactions?
The ABO system of carbohydrates
What are the four human ABO blood groups?
A, B, AB, O
What is the genetic possibility for homozygous
blood type A?
AA
What is the genetic possibility for heterozygous
blood type A?
AO
What is the genetic possibility for homozygous
blood type B?
BB
What is the genetic possibility for heterozygous
blood type B?
BO
What is the genetic possibility for homozygous
blood type AB?
none
What is the genetic possibility for heterozygous
blood type AB?
AB
What is the genetic possibility for homozygous
blood type O?
OO
What is the genetic possibility for heterozygous
blood type O?
none
Which blood group am I? I have B antigen on the RBC and Anti-A antibody in blood.
B
Which blood group am I? I have A and B antigen on the RBC and don’t have A or B antibody in blood.
AB
Which blood group am I? I have A antigen on the RBC and Anti-B antibody in blood.
A
Which blood group am I? I don’t have A or B antigen on the RBC and have both Anti-A and Anti-B antibody in blood.
O
What is the Rh factor?
The Rh factor (Rhesus factor) in blood refers to a specific antigen found on the surface of red blood cells. It can be either Rh-positive (if the antigen is present) or Rh-negative (if the antigen is absent).
What is the universal donor blood type?
O
What is the universal recipient blood type?
AB
What is an allergic reaction?
An allergic reaction is when someone is overly reactive to a substance that most others tolerate well.
What are the two types of allergic reactions?
Immediate Hypersensitivity
Delayed Hypersensitivity
What is immediate hypersensitivity?
Immediate hypersensitivity is a type of allergic
reaction that occurs within minutes of exposure to
an allergen.
What leukocytes are involved in the allergic reactions?
Mast cells and basophils filled with granules with histamine
What is anaphylaxis?
Anaphylaxis is a sequence of events that can cause death due to circulatory and respiratory failure, and is caused by large amounts of mast cell (or basophil) chemicals entering the circulation.
What is an autoimmune disease?
An autoimmune disease is an inappropriate immune attack triggered by body proteins acting as antigens, and the immune attack, mediated by
autoantibodies and self-reactive T cells, is directed against body cells that contain these proteins.
