Immunology 2 Flashcards
What do Interferon Alpha and Beta do?
Part of the innate immune systems defence against both RNA and DNA. Interferons are glycoproteins synthesized by viral-infected cells that act locally on uninfected cells, “priming” them for viral defense.
What are the two steps of “priming” interferon Alpha and Beta?
- RNAase L - degradation of viral/host mRNA2. Protein kinase - inhibition of viral/host protein synthesis These two steps essentially result in apoptosis, thereby interrupting viral amplification
Where do we find/see cell surface proteins?
All cells except mature RBCs have MHC1
What cell surface receptors are present on T cells?
TCR (bind antigen-MHC complex)CD3 (associated with TCR for signal transduction) CD28 (binds B7 and APC)
What cells surface receptors are present on Helper T Cells?
CD4, CD40l
What cell surface receptors are present on Cytotoxic T cells?
CD8
What cell surface receptors are present on B cells?
Ig (binds antigen)CD19, CD20, CD21 (receptor for EBV)CD40MHC2, B7
What cell surface receptors are present on Macrophages?
CD14, CD40MHC2, B7Fc and C3b receptors (enhance phagocytosis)
What cell surface receptors are present on NK cells
CD16 (binds Fc of IgG)CD56 (unique marker for NK)
Define Anergy
A state of immune unresponsiveness
What effects can bacterial toxins have?
- Pathogens like S. progenies and S. aureus, cross-link the Beta region of the T-cell receptor to the MHC class 2 on APCs.
- Can activate any T cell, leading to massive release of cytokines
- Endotoxins/lipopolysaccharide (gram-negative bacteria) - directly stimulate macrophages by binding to endotoxin receptor CD14; Th cells are not involved
Define Antigenic Variation
Mechanism by which an infectious organism such as a protozoan, bacterium or virus alters its surface proteins in order to evade a host immune response
Provide an example of antigenic variation
- DNA rearrangement
- RNA segment reassortment (eg. influenza major shift)
How do you acquire passive vs. active immunity
passive = receiving preformed antibodies active = exposure to foreign antigens
Describe the difference in the onset of passive vs. active immunity
Passive = rapid Active = slow
Compare duration of a passive vs. active immune response
Passive = short lasting Active = long lasting
Name 4 pathogens, given as vaccines, that provide passive immunity via preformed antibodies
TO BE HEALED RAPIDLY - Tetanus, Botulinum toxin, HBV, Rabies vaccines
What other terms/words are used in the place of active immunity?
Active immunity = humoral immunity = cellular immunity
Describe Live Attenuated Vaccines
Microorganism loses its pathogenicity but retains capacity for transient growth within inoculated host. Mainly induces a CELLULAR RESPONSE
Describe Inactive or Killed Vaccines
Pathogen is inactivated by heat or chemicals; maintains epitope structure on surface antigens is important for immune response. HUMORAL IMMUNITY induced.
List 1 pro and 1 con of live attenuated vaccines
PRO - induced strong, often lifelong, immunity
CON - may revert to virulent form, Often contraindicated in pregnancy and immune def.
List 1 pro and 1 con of inactived/killed vaccines
PRO - stable and safer than live vaccines
CON - weaker immune response; booster shots are usually required
List some live attenuated vaccines
MMRPV
- measles
- mumps
- rubella
- polio (Sabin)
- influenza
- varicella
- yellow fever
List some inactivated/killed vaccines
- cholera
- hep A
- Polio (Salk)
- Influenza (inj)
- rabies
What type of reaction is a type 1 hypersensitivity response?
Anaphylactic and atopic (First and Fast)
Which types of hypersensitivity reactions are antibody mediated?
Types 1,2 and 3
How do type 1 hypersensitivity reactions work?
- free antigen cross-links IgE on a pre-sensitized mast cells and basophils.
- This triggers immediate release of vasoactive amines that act as post capillary venues (i.e histamine).
- This reactions develops quickly because of preformed antibodies
- delayed response follows due to production of arachadonic acid metabolites (e.g leukotrienes)
What is responsible for the rapid response of type 1 hypersensitivity?
preformed antibodies (e.g. histamine)
What is responsible for the delayed response that follows the rapid response of the type 1 hypersensitivity?
arachadonic acid metabolites (e.g leukotrienes)
What types of reaction is a type 2 hypersensitivity?
Cytotoxic
How do type 1 hypersensitivity reactions work?
IgM, IgG bind to fixed antigen on “enemy” cells, leading to cellular destruction.
3 mechanisms
1. opsonization leading to phagoctosis or compliment activation
2. complement-mediated lysis
3. antibody- dependent cell-mediated cytotoxicity, usually due to NK cells or macrophages
How do type 3 hypersensitivity reactions work?
Imagine an immune complex with 3 things stuck together - antigen, antibody, complement.
This complex activates complement, which attracts neutrophils; neutrophils release lysosomal enzymes
What types of hypersensitivity reaction is responsible for serum sickness?
Type 3
How does serum sickness arise?
A type 3 hypersensitivity response by the immune system.
An immune complex forms in which antibodies to the foreign proteins are produced (takes 5 days). Immune complexes form and are deposited in membranes, where they fix complement (leads to tissue damage). More common than Arhus reaction.
What are the symptoms of serum sickness?
Fever, urticaria, arthralgias, proteinuria, lymphadenopathy, 5-10 days after antigen exposure
What is an arthrus reaction?
A local, subacute antibody mediated hypersensitivity (type 3) reactions.
Intradermal injection of an antigen induces antibodies, which form antigen 0 antibody complexes in the skin.
What are the symptoms of Arthrus Reactions?
Edema, necrosis, activation of complement
What causes Arthrus reactions?
Antigen-antibody complexes
What is another name for Type 4 hypersensitivity?
Delayed (T cell mediated) hypersensitivity
How does Type 4 hypersensitivity work?
Sensitized T lymphocytes encounter antigen and then release lymphokines (leads to macrophage activation; no antibody involved)
List the 4 types of hypersensitivity reaction with their number and name
Type 1, anaphylactic and atopic
Type 2, Cytotoxic
Type 3, Immune complex
Type 4, Delayed (T cell mediated) type
What types of hypersensitivity reaction causes anaphylaxis?
Type 1
What types of hypersensitivity reaction causes allergies atopically
type 1
What types of hypersensitivity reaction causes SLE
type 3
What types of hypersensitivity reaction causes Autoimmune hemolytic anemia?
type 2
What types of hypersensitivity reaction causes Pernicious anemia?
type 2
What types of hypersensitivity reaction causes MS?
Type 4
What types of hypersensitivity reaction causes Polyarteritis nodosa?
Type 3
What types of hypersensitivity reaction causes idiopatic throbocytopenia purpora
Type 2
What types of hypersensitivity reaction causes Erythroblastosis fettles?
Types 2
What types of hypersensitivity reaction causes Poststreptococcal glomerulonephritis?
Type 3
What types of hypersensitivity reaction causes Acute hemolytic transfusion reactions
Type 2
What types of hypersensitivity reaction causes Guillain-Barre Syndrome?
Type 4
What types of hypersensitivity reaction causes graft-vs-host disease?
Type 4
What types of hypersensitivity reaction causes Serum Sickness
Type 3
What types of hypersensitivity reaction causes PPD (test for M. tuberculosis)
Type 4