Immunity Flashcards
(88 cards)
<p>Immunne system</p>
<p>A collection of mechanisms that protect against disease by identifying and killing pathogen and tumour cells, and protection against microbial toxins. </p>
<p class=”large” style=”text-align:center”;>Pathogens</p>
<p class=”large” style=”text-align:center”;>Viruses, bacteria, mycobacteria, parasites, fungi. </p>
<p>What are the 5 general characteristics of immunity?</p>
<p>Recognition, Specificity, Regulation, Amplification, Memory</p>
<p class=”large” style=”text-align:center”;>Recognition (characteristic of immunity)</p>
<p class=”large” style=”text-align:center”;>Distinguish between normal self, altered self, and non-self. </p>
<p>Specificity (characteristic of immunity)</p>
<p>Inactivate/destroy/remove material without damaging normal tissues. </p>
<p class=”large” style=”text-align:center”;>Regulation (characteristic of immunity)</p>
<p class=”large” style=”text-align:center”;>Control the type, intensity, and duration of reaction and prevent it. </p>
<p>Amplification (characteristic of immunity)</p>
<p>The effector (attack) phase of humoral immunity, which is brought by many pathways, can be amplified or activated individually. </p>
<p>Characteristics of innate immunity</p>
<p>1) exposure leads to maximal response
2) non-specific
3) doesn't require previous exposure
4) found in nearly all life-forms</p>
<p class=”large” style=”text-align:center”;>Characteristics of adaptive immunity</p>
<p class=”large” style=”text-align:center”;>1) pathogen/antigen specific
2) lag between exposure and response
3) cell-mediate and humoral (antibody) components
4) inflammatory response
5) memory
6) found only in jawed vertebrates</p>
<p>What happens in innate immunity?</p>
<p>Happens when an organism breaks through the epithelial barriers; phagocytes inject microbes and secrete cytokines to stimulate the inflammatory response. </p>
<p class=”large” style=”text-align:center”;>What two cells act in innate immunity?</p>
<p class=”large” style=”text-align:center”;>Cytokines and phagocytes. </p>
<p>Components of innate immunity:</p>
<p>1) surface barriers (mechanical, biological, and chemical)
2) Humoral and chemical barriers (inflammation and complement system)</p>
<p class=”large” style=”text-align:center”;>What cells can produce inflammation?</p>
<p class=”large” style=”text-align:center”;>Cytokines (i.e., interleukins), prostaglandins, leukotrienes, chemokines, interferons.</p>
<p>What do neutrophils do during inflammation?</p>
<p>phagocyte and release enzymes</p>
<p class=”large” style=”text-align:center”;>What do eosinophils/basophils do during inflammation?</p>
<p class=”large” style=”text-align:center”;>secrete chemical mediators</p>
<p>What do monocytes/macrophages do during inflammation?</p>
<p>engulf pathogens and digest them via lysozomes</p>
<p class=”large” style=”text-align:center”;>What do mast cells do during inflammation?</p>
<p class=”large” style=”text-align:center”;>regulate the immune response</p>
<p>What do dendritic cells do during inflammation?</p>
<p>phagocyte microbes</p>
<p class=”large” style=”text-align:center”;>What do dendritic cells do during acquired immunity?</p>
<p class=”large” style=”text-align:center”;>phagocyte microbes</p>
<p>What do natural killer cells do during inflammation?</p>
<p>Kill cells that don't express or inappropriate express MHC class I; produce cytokine interferon-y to activate macrophages.</p>
<p class=”large” style=”text-align:center”;>What do natural killer cells do during adaptive immunity?</p>
<p class=”large” style=”text-align:center”;>Recognize and kill IgG-coated cells (antibody dependent cell-mediated cytotoxicity)</p>
<p class=”large” style=”text-align:center”;>What is the complement system?</p>
<p class=”large” style=”text-align:center”;>20 proteins that can form many combinations and cause various responses; they are produced in the liver.</p>
<p>What activates the complement system?</p>
<p>Proteases, binding with antibodies/carbs that are attached to microbes, endotoxins and mannose residues.</p>
<p class=”large” style=”text-align:center”;>What are the mechanisms of the complement system?</p>
<p class=”large” style=”text-align:center”;>- lysis of target cell
- opsonization of target organism
- attraction of other immune cells via peptides
- release in factors that create inflammation (chemoattractants)
- trigger the coagulation system (kinin, fibrinogen)</p>
What is the Toll-like receptor?
A receptor on phagocytes that can recognize bacterial products (endotoxins), viruses (dsDNA), and more.
Adaptive immunity depends on:
Lymphocytes, antigen presenting cells (APCs), and phagocytes.
How does adaptive immunity achieve specificity?
Recognition of specific antigens and expression of MCH.
What drives this system to be so far-reaching?
Hypermutation in somatic immune cells and V(D)J recombination of antigen receptor genes creating a huge number of unique antigens, with one on each lympocyte.
Components of adaptive immunity:
Lymphocytes (T, B, NK cells), MHC, phagocytes, and antigen presenting cells (dendritic cells and macrophages)
What is the origin of T-Lymphocytes?
Originate from primitive stem cells (yolk sac in embyros and bone marrow after birth) and mature in the thymus gland.
What is the function of T-lymphocytes?
Recognize specific cell-bound antigen by means of antigen-specific T-Cell Receptor (TCR), which are linked to 5 polypeptide chains called the CD3 molecular complex.
What is the CD3 molecular complex?
In T-lymphocytes, they bind to the receptor cytoplasmically and transduce signals into the cell after antigen binding.
What is the CD4 molecular complex?
In 60% of mature CD3+ cells, they provide Helper/inducer functionality.
What is the CD8 molecular complex?
In 30% of T cells, they provide suppressor/cytotoxic functionality.
What presents antigens to T cells?
Antigen presenting cells, namely accessory cells.
T/F: There are more B cells than T cells.
False; 60% T cells, 10-20% B cells. The rest are NK cells.
Where do B cells originate from?
Same as T cells (yolk sac/bone marrow), but they mature in bone marrow as well.
What is the mechanism of action of B cells?
On antigenic stimulation, they proliferate and form plasma cells that secrete 5 classes of Igs (MGADE), and memory B cells.
What kinds of receptors are there on the B-cells?
IgM antigen receptor complex (mostly), and complement receptors, IgA and IgE, CD40, and Fc receptors.
What do B cells absolutely require for their maturation?
T cells and other non-specific factors (i.e., bacterial products)
Why are macrophages important in adaptive immunity?
As phagocytic cells, they process and present antigens to T cells by engulfing opsonized microbes in humoral immunity.
Give an example of cell-mediated immunity where macrophages are imporant:
Delayed hypersensitivity (i.e., alergies)
What is the difference between humoral and cell-mediated immunity?
Humoral has to do with pathogens in the blood stream, while cell-mediated has to do with pathogens in cells.
What are the two types of dendritic cells (APCs) and what is the difference between them?
Interdigiting - express MHC Follicular - express Fc receptors for IgG
Name the affect of inteferon and prostaglandin on NK cells.
Interferon promotes their killing activity, while prostaglandinds suppress them.
What two receptors do NK cells bear?
CD16 and CD56 only. NOT TCRs.
What are the 3 classes of MHC and their function?
Class I - present on all nucleated cells and recognized by cytotoxic T-cells and NK cells. Class II - Antigent presenting cells, B cells, and some activated T cells; recognized by CD4+ helper T cells. Class III - compliment antigen, not histocompatibility.
What is the function of helper T cells?
Activate other cell types involved in immunity via cytokines (interleukin-2) and the CD40 ligand
What is the function of interleukin-2?
Secreted by helper T cells, they cause proliferation of a specific T cell (allowing amplification of response).
What to cell types can arise from helper T cells that secrete IL-2?
TH1, TH2, and TH17 cells.
What is the function of TH1 cells?
Release IFN-y, which activates phagocytosis, antibody production in B cells, and production of antimicrobial substances in macrophages.
What is the function of TH2 cells?
Secrete IL-4/5/13, which activate mast cells and eosinophils.
What is the function of TH17 cells?
Secrete IL-17, which activates neutrophils.
What cell types arise from cytotoxic (CD8+) T cells?
Cytotoxic lymphocytes.
What is the function of cytotoxic lymphocytes?
Recognize infected cells via MHC I and release granules of perforin and granzyme-B into these cells (perforin allows entry of granzyme-B).
What does granzyme B do and what secretes it?
Cytotoxic lymphocytes, and it causes apoptosis via proteolytic cleavage and activation of capsases.
What cells types arise from B cells in humoral immunity?
Plasma cells and memory B cells.
Can B-cells be activated by non-T-cells?
Yes, but lipid or polysaccaride antigens (which may activate several different B cells)
What are the five antibodies secreted by B cells in humoral immunity?
GMADE! IgG - opsonize microbe, activate complement (crosses placenta) IgM - activate complement IgA - secreted in mucosal tissues IgD - unknown! IgE - costs parasites, activates mast cells and eosinophils
What is antibody dependent cell-mediated cytotoxicity?
Neutrophils, macrophages, and NK cells have surface receptors to the Fc portion (non-variable) of antibodies, which allows them to non-specifically destroy cells/microbes.
Which two cells are long lived and allow fast response to recognized antigens?
Memory B cells and T-cells.
What are the two main forms of disease from hypofunction of the immune system?
Defense and Surveillance
What are disorders of defense?
Increased succeptibility to infection.
What are disorders of surveillance?
Increase frequency of malignant disease.
What is the end result of hypersensitivity?
Damage to body tissues.
What are the four types of immune reactions that lead to tissue damage or disease>
Type I: Anaphylactic, Type II: Antibody-mediated, Type III: Immune complexes, and Type IV: Cell-mediated.
What is the mechanism of Type I hypersensitivity?
Release of vasoactive amines through TH2 helper T-cells, which activate IgE-producing B cell; IgE will stimulate mast cells to release histamine. Ultimately increases vascular permeability and smooth muscle contraction.
What is the mechanism of Type II hypersensitivity?
IgG or IgM antibodies are produced; in addition to activating the complement system, they bind to Fc receptors on phagocytes. This causes non-specific engulfing of circulating opsonized cells and imflammation.
What kind of reaction occurs in transplant patients?
Type II hypersensitivity!
What is the mechanism of Type III hypersensitivity?
Antigen/antibody complexes are trapped in organs, where they produce injury by complement and neutrophil activation. Examples: systemic lupus erythematosus, post-streptococcal glomerulonophritis.
What is the mechanism of Type IV hypersensitivity?
Trick question! There are two types (delayed type mediated by CD4 cells, and T-cell-mediated cytotoxicity mediated by CD8 cells.
What is the mechanism of delayed type hypersensitivity?
CD4 cells differentiate into either TH1 or TH17 cells. These may then form granulomas if the pathogen persists. Example: Tuberculosis, poison, etc.
What is the mechanism of T-cell-mediated cytotoxic hypersensitivity?
CD8 cells destroy cell expressing self-antigens. Example: Type I diabetes (islet cells in pancreas)
Symptoms of autoimmune disease depends on what 3 factors?
a) the target (antigen) b) type of immune reaction (cell-mediated, humoral, or both) c) secondary changes (due to immune response or loss of organ)
What are the clinical symptoms of system lupus erythematosus?
a) DNA is the target b) Type III immune rection (circulating DNA/anti-DNA complexes) c) Dermatitis, nephritis, arthritis
What are the symptoms of Hashimoto's thryroiditis?
a) thyroid follicular cells are the target b) Type II and IV hypersensitivity c) Hypothyroidism due to destruction of thyroid cells
What are the clinical feaures associated with immunodeficiency?
1. Chronic infection 2. Recurrent infection 3. Unusual infecting agent (low virulence) 4. Poor resolution or poor response to antibiotic treatment
In primary (congenital) immunideficiency, why is pure T cell deficiency unlikely?
Because there is also a lack of helper effect on B cells.
Give an example of a pure B cell dysfunctive immunodeficiency.
Bruton's syndrome (not detected until 5-6 months, because of protection by maternal IgG antibodies.
Which Ig can cross the placenta?
IgG
T/F: Both T and B cell deficiency can occur in the same patient.
True (i.e., severe combined immunodeficiency disease)
Give an example of a cell-mediate immune deficiency syndrome.
DiGeorge syndrome - congenital absence of thymus.
What are some primary immunodeficiency disorders affect lymphocyte function (adaptive immunity)?
a) X-Linked agammaglobulinemia b) Common variable immunodeficiency c) Isolated IgA deficiency d) Hyper IgM syndrome e) DiGeorge syndrome f) severe combined immunodeficiency
If a patient has intact B and T cell function, why are recurrent infections still possible?
Because there may be defects in the amplification systems
Phagocytic dysfunction (absence of lysosomal enzymes in monocytes and granulocytes) can lead to what common disease?
Chronic granulomatous disease
What are some primary immunodeficiency disorders affect innate immunity?
a) Deficiency of complement proteins b) Chronic granulomatous disease (defect in NADPH oxidase) c) Rare mutations in Toll-like receptors (TLRs)
What are the causes of secondary immunodeficiencies?
a) Infections b) Immunosupressive therapy (cytotoxic drugs, irradiation, anti-lymphocyte serum globulin (ALG) c) Malignancy d) Chronic illness e) Malnutrition f) Aging
Name four common diseases that secondary immunodeficiences caused by infections.
Rubella, Measles, Mycoplasma, and HIV
