Immunology Flashcards
Difference between Non-Specific/Innate immunity and Specific/Adaptive Immunity
Innate: First-line of defense
Not need to Recognize pathogen, same response for each pathogen
Adaptive: must recognize pathogen
faster response in second exposure to pathogen
What are main components of immune system
Lymphoid Organs:
primary
secondary
Immune cells: Leukocytes
Secretion of Immune Cells
Primary Lymphoid Organs
Site for stem cells division and immune cells development
Bone Marrow
Thymus
Role of Bone marrow in immunology
Production of B-cells and immature T-cells
Maturation site of B-cells
What is role of Thymus
Contains T cells, scattered dendritic cells, epithelial cells, macrophages
Maturation site of T-cells
What happens to Thymus as time goes by
It shrinks
Leads to weaker immune response
Secondary lymphoid organs
Lymph nodes
Spleen
Lymphoid Nodules
What does spleen do in immunology
Removes microbes and old erythrocytes
In what do immune cells travel
Blood and lymph
What is role of lymph nodes
filter bacteria
site for phagocytosis of microbes
Functions of neutrophils
Phagocytosis
Release chemicals involved in inflammation (vasodilators, chemotaxins)
Functions of basophils
Release variety of chemicals, histamine, prostaglandins
Functions of Eosinophils
Destroy multicellular parasites
help hypersensitivity reaction
functions of Monocytes
Transform into Macrophages and Dendritic cells to do Phagocytosis
Lymphocytes functions
Recognition cells in specific immune responses
B cells functions
antibody-mediated immune response, bind to specific antigens to B-cell plasma membrane receptors
Become plasma cells when activated and secrete antibodies
present antigen to helper T cells
Cytotoxic T cells functions
Bind to antigens on plasma membrane of target and directly destroy the cell
Helper T cells functions
Secrete Cytokines that activate B cells, cytotoxic T cells, NK cells and macrophages
Macrophages Functions
Phagocytosis
present antigen to helper T cells
Secrete cytokines : inflammation, activation of helper T cells
Dendritic Cells functions
Phagocytosis, antigen presentation, Professional APC (Antigen presenting cell)
Mast cells functions
Release Histamine and other chemicals involved in inflammation
Characteristics of innate immunity
First line of defense: physical barriers
second line of defense: cellular factors
humoral factors
What is the first line of defense of innate immunity
Skin
Additional physical/mechanical barriers: mucus, hair, cilia
Chemical and microbiological barriers, secretions: sebum, gastric juice, lysozyme
What makes the second line of defense of innate immunity
Humoral factors:
inflammation, fever
antimicrobial substances
interferons
Cellular factors:
Phagocytic cells
cells with inflammatory mediators
Natural killer cells
Stages of inflammation
- Vasodilation: more blood flow to site, membrane is more permeable for defense substances to reach site
- Emigration of phagocytes
- tissue repair
Interferons functions in humoral response
Discourage microbial growth or spread of pathogen in surrounding healthy cells
Complement plasma proteins (C3b) functions in humoral response
Protein receptors that stick to pathogens and make it recognizable to be eaten by phagocytes
Natural Killer Cells (NK Cells) functions/roles
Target virus-infected cells and cancer cells
Not antigen-specific
Don’t need to recognize antigen
How do NK cells kill cells
Release chemicals (granzyme) on cells not expressing MHC-1
Attack and kill cells directly after binding to them
Importance of MHC Class 1
Proteins are expressed on normal cells, so when NK cells binds to them, it moves on to the next cell without killing the normal cell.
no MHC class 1 = no negative signal, so NK cells is activated and kills cell
Where are old RBC phagocytosed
in the spleen
Main role of Phagocytes
non-specifically engulf microbial invaders
Types of phagocytes
Fixed-tissue Macrophages
neutrophils
Monocytes
How are microbe destroyed
When ingulfed in phagocytes, bacteria is hold in a phagosome by endocytosis
phagosome fuses with lysosome and bacteria is digested
Waste is released either in our out of cell
How do phagocytes recognize microbes
Detect unique structures essential to microbial physiology (pathogen-associated molecular patterns) PAMPs
What are Pattern Recognition Receptors PRR: Toll-Like Receptors (TLRs)
Transmembrane receptors on macrophages essential for microbial recognition via PAMPs
TLR:
Extracellular domain for pathogen recognition
Intracellular signaling domain
What type of response is Inflammation
Non-specific response to tissue damage
what is chemotaxis
chemically stimulated movement of phagocytes
Chemokines and Chemoattractants are the chemicals attracting phagocytes
What happens to Neutrophils when they kill bacteria
Neutrophils die
Spill NETs: neutrophil extracellular traps which slow down bacterial movement
what is pus
Mixture of dead bacteria and neutrophils
Types of antigen
Material that induces an immune response (immunogen)
also, allergen
ligand (binds to receptors)
what antigen stands for
Antibody Generator
whole cell or part of a cell
can be non-microbial
ex: pollen, egg whites, incompatible blood, transplanted tissues
what is an epitope
part of antigen recognized by antibody
How is specific immunity activated
Dendritic Cells pick up bacteria and bring it back to lymph nodes to find antibody to counter antigen
What mediates specific/adaptive immunity
Antibodies or cells
Humoral-Antibody-mediated immunity
Involves B lymphocytes (maturation in bone marrow)
Requires antigen presenting cell (dendritic cell)
transform into plasma cells in secondary lymphoid organs
synthesize and secrete antibodies
Memory B cells
Cell-mediated adaptive immunity
Involves Cytotoxic T cells (maturation in thymus)
requires recognition of antigen by dendritic cells
Kill infected body cells, cancer cells, foreign cells
2 types of Major Histocompatibilty Complex (MHC)
MHC I: on all nucleated cells
MHC II: expressed on antigen-presenting cells: macrophages, dendritic cells, B-cells
MHC molecules are different for every person
What is Adaptive immunity
Defense against specific microbes which involves memory from previous encounters with antigen
B and T cells recognize specific pathogen
3 stages of adaptive immune response
Recognition of antigen by lymphocytes
Lymphocyte activation
Attack by activated lymphocytes and their secretions
Role of helper T cells
Recognize Antigen from MHC II of APC
to
Activate B cells and Cytotoxic T cells by sending Cytokines
Events required for activation of helper T cells
- Specific Recognition
(MHC II + peptide, antigen) - T Cell receptor - Co-reception (at same time)
CD28 (T cell) - B7 (APC) - Cytokine release from APC
Stimulates T helper cell
Checkpoint inhibition for helper T cells
CTLA4 displaces CD28 and breaks bond with B7
CTLD4 binds with B7 to shut off process
What is anti-CTLA4
Artificial protein that sticks to CTLA4 to prevent it from inhibiting helper T cells
What are antibodies
Proteins called globulins (Immunoglobulins = Ig)
Structure of Antibodies
Contain four polypeptide chains
2 identical heavy chains
2 identical light chains
Within light/heave chains
Variable region
Constant region
What is the variable region of an antibody
Antigen binding site
FAB region = antigen binding fragment, hypervariable region
Must vary to cover all potential antigens
Characteristic of constant region of antibody
FC region:
Same in all antibodies of a certain class
5 classes of antibodies
IgG: most numerous, cross placenta
IgA: in MALT, mucosal associated lung tissues, breast milk
IgM: first formed, decavalent = bind to 10 antigens, can be activated into other antibodies
IgD: prenatal
IgE: allergy
Antibody-Mediated immunity process
B cells are activated in secondary lymphoid organs: spleen, lymph node, lymphoid nodule, in presence of microbe
Cloning begins to produce
Plasma cells secreting specific antibodies
Memory cell for faster response if antigen comes back
Active antibody-mediated immunity process
Person’s own immune system responds to a pathogen resulting in long last protection from memory cells
Natural: develops from exposure to natural antigen
Artificial: Develops with purposeful exposure to antigen (vaccine)
Passive antibody-mediated immunity process
Person receives antibodies from other source: temporary protection = no memory cells
Natural: IgG from mother to fetus across placenta, IgA in breast milk (no immune system response)
Artificial: Receive serum containing antibodies from other person/animal
Antibody function: neutralizing antigen
if antigen is a toxin, combination with antibody can cancel toxic effect
Antibody function: Agglutinating Antigen
Antibody immobilises bacteria to allow macrophages to consume them
antibody function: Precipitating antigen
If antigen is soluble, antibody can transform it into precipitation which can then be consumed by immune cells
Antibody function: Activating Complement
Antibody activates complement protein and allows it to kill microbes
Antibody function: Opsonization
Antibody is an opsin = allows phagocytes to ingest bacteria more easily by tagging them
Antibody-Dependent Cellular Cytotoxicity via Natural Killer Cells
Receptors for Fc portion of an antibody is expressed on surface of NK cells
antibody binds with specific target
Binding Activates release of Granzymes and perforin from NK cell
What is clonal expansion
Activated lymphocytes express receptor for specific antigen which leads to production of memory cells : B cells, helper T cells, cytotoxic T cells
memory cells expand pool of lymphocytes with receptor, so it allows for quicker immune response if antigen comes back
Complement Cascade process
Antibody binds to complement proteins
Afterwards, binds to antigen and activates Membrane Attack Complex
Membrane Attack Complex
Complements that form a channel in the microbe cell wall to make it spill its insides out (kill it)
Role of RAG (Recombination Activating Genes)
Splice out gene Segments : VDJ to form DNA segments for heavy chain of antibodies
Why do we still get sick
First exposure to pathogen, antibodies production is not quick enough
Terminal deoxynucleotidyl Transferase, TdT role
Add additional nucleotides at junctions between VDJ genes to give more variety (almost infinite)
What is immune tolerance
Clonal deletion or clonal inactivation of cells that match body antigens to protect own body cells
What happens to T cells that recognize self-proteins MHC Class I
They are destroyed
What happens to T cells that cannot recognize MHC Class II
They are destroyed
What percentage of T cells are destroyed
95%
What type of Antigen can Cytotoxic T cells recognize
Endogenous Antigen
recognizes MHC I - Antigen complex on plasma membrane
What is an Endogenous Antigen
An antigen produced by body cells when they detect the presence of viral content inside them
How do Cytotoxic T cells operate
when virus infects cells, Cytotoxic T cells bind to Viral antigen on MHC Class I proteins
Tc Cells are activated by Cytokines send by Helper T cell that also recognize the antigen of the MHC II protein of a APC
Tc Cells are cloned, some stay as memory cells, the rest go fight the viral agents by sending perforin and granzymes on them
Factors altering resistance to infection
Malnutrition
Preexisting disease
Stress and state of mind
Sleep deprivation
Minimal exercise and physical activity
What is AIDS
Acquired ImmunoDeficiency Syndrome
it infects and kills helper T cells, so immune response to pathogens and cancer is greatly diminished
cannot activate B and Tc cells
What is SCID
Severe Combined Immunodeficiency Disease
Disease related to absence of B and T cells and sometimes NK cells
Harmful immune responses from Tissue/graft rejection
Different MHC I proteins of graft cells from Recipient’s MHC II proteins on macrophages causes recipient’s Tc cells with Th cells to attack MHC I proteins judged as foreign
How to avoid rejection during organ transplantation
Drugs that kill actively dividing lymphocytes ( T cells)
Cyclosporine blocks cytokine production from Helper T cells
However, patients are more susceptible to infections
Antigen and antibodies of Blood group A
Antigen: A
Antibody: anti-B
Antigen and antibodies of blood group B
Antigen: B
Antibody: anti-A
antigen and antibodies of blood group AB
antigen: A and B
antibody: neither Anti-A and Anti-B
Antigen and antibodies of blood group O
antigen: neither A nor B
antibodies: Both anti-A and anti-B
Universal Donor
O group when purified of antibodies
universal receiver
AB
What is Rh factor
+ or - additional factor
Types of allergic reactions
Immediate hypersensitivity
delayed hypersensitivity (12-72h after)
What is Anaphylaxis
Allergic symptoms can cause mast cells (granulocytes with vesicles) accumulation resulting in hypotension, bronchiolar constriction
Autoimmune disease definition
Inappropriate immune attack triggered by body proteins acting as antigens
