Immunology Flashcards
What antibody is most effective in activating complement? Why?
IgM.
Pentameric antibody so it has the largest surface area.
What is the first antibody secreted after encounter with an antigen?
IgM
What does “ MHC is polygenic” mean?
It contains several different MHC class I and class II genes. Every individual possesses a set of MHC molecules with different peptide binding clefts.
What does “ MHC is polymorphic” mean?
There are multiple variants (alleles) of each gene within the population as a whole.
Name the three ‘major’ immunoglobulins.
IgM, IgG, IgA
Name the Penatmeric, Dimeric and Monomeric antibodies.
Pentameric - IgM
Dimeric - IgA
Monomeric - IgG, IgD, IgE
What are Langerhans cells?
Dendritic cells found on the skin
(majority found in the stratum spinosum)
What activates
a) classical pathway?
b) lectin pathway?
c) alternative pathway?
a) IgM, IgG, CRP
b) manose binding lectin binding to the pathogen
c) triggered by changes in the environment due to the pathogen.
Name the anaphylatoxins.
C3a and C5a.
Cause degranulation of mast cells.
Also cause bronchoconstriction & vasodilation.
Attract and activate n’s and m’ to site of injury.
What do the three pathways converge on?
Activation of C3
Generation of C5 convertase
What does C5 convertase do?
Splits C5 into
C5a - chemotactic agent
C5b - remains attached to the pathogen and begins the terminal pathway to create MAC.
What are the three final outcomes for the complement system?
- Chemotaxis = recruitment of inflammatory cells.
- opsonisation (via C3b and C4b) for phagocytosis.
- cell lysis - via MAC.
All result in death of the pathogen.
What are the two types of MHCs?
What does each do?
Type 1 and type 2.
[1] –> presents antigens from intracellular pathogens e.g. virsues to cytotoxic T cells.
[2] –> presents antigens from extracellular pathogens e.g. bacteria to T helper cells.
How MHC 1 and 2 differ in structure?
MHC 1
1 large polypeptide that contains three extracellular domains which is anchored to the plasma membrane. The smaller polypeptide is not anchored.
MHC 2
2 large polypeptides with two extracellular domains which are both anchored to the plasma membrane.
How can a cytotoxic T cell be distinguished from a T helper cell?
cytotoxic T cell express the protein CD 8
T helper cell express the protein CD 4
What are CD4 and CD8 molecules called?
Where do they bind?
T cell ‘co’ receptors.
CD4 binds to a site on the MHC 2 molecle that is separate from the binding site of the T cell receptor.
CD8 binds to a site on the MHC 1 molecle that is separate from the binding site of the T cell receptor.
What is the outcome for
CD8 T cell + virus infected cell?
death of virus infected cell
What is the outcome for
CD4 T cell + macrophage?
The macrophage is involved in pahocytosis of the bacteria already. Binding of CD4 T cell improves the phagocytic activity of the macrophage causing cytokines to be released.
What is the outcome for
CD4 T cell + B cell?
The B cell has its antigen bound. It causes secretion of cytokines which cause B cells to differentiate into antibody secreting plasma cells.
The antigen binding site of an immunoglobulin is formed from __ ?
The paired V regions of a single heavy chain and a single light chain.
What is the hypervariable region?
Located within the variable region - vaires greatly between different antibodies.
What is the constant region?
The most conserved region of the molecule with limited variation between antibodies.
Which diagram represents
a) CD4 and MHC 2
b) CD8 and MHC 1
What properties are linked to IgA?
(hint: 2 )
5,9
What properties are linked to IgD?
(hint: 1)
7
What properties are linked to IgE?
(hint: 2)
6,7
What properties are linked to IgG?
(hint: 6)
1,2,3,4,6,8
What properties are linked to IgM?
(hint: 1)
2
Mucosal epithelia of the GI tract, respiratory tract etc is protected by what?
dimeric IgA
Give some examples of passive transfer of immunity.
- transfter if IgG across the placenta during foetal development.
- transfer of IgA through breast milk.
- intravenous immunoglobulin therapy for immunocompromised individuals.
What type of bacteria is Clostridium difficile?
Gram positive
bacillus
anaerobic
What complement proteins make up C3 convertase?
(two options)
What happns to C3 convertase after this?
C3bBb (from alternative pw)
C4bC2a (from classical/MBL)
Cleaves C3 –> C3a and C3b
In alternative, C3bBb + C3b = C3bBb3b (C5 convertase) –> C5b & C6-9 –> MAC
In classical/MBL, C4bC2a + C3b = C4bC2a3b (C5 convertase)
What factor is required for cross linking of fibrin monomers?
Fibrinpeptide A release forms __?
Fibrinpeptide B release forms __?
Factor 13 ( –> F13a)
Fibrinogen -> Fibrin monomers -> Polymer
*F13a* -> Cross linked fibrin polymer
Fibrinpeptide A release forms proteofibrils
Fibrinpeptide B release forms side to side polymer
What do these serologic tests conclude about whether or not this person is / has been affected by Hep B?
They are SUSCEPTIBLE.
Haven’t been vaccinated or infected in the past (therefore no natural immunity)
What do these serologic tests conclude about whether or not this person is / has been affected by Hep B?
They are IMMUNE due to natural infection.
The anti-HBc represents past infection.
What do these serologic tests conclude about whether or not this person is / has been affected by Hep B?
They are IMMUNE due to the hep B vaccine.
The hep B vaccine gives you the surface antibody.
What do these serologic tests conclude about whether or not this person is / has been affected by Hep B?
They are ACUTELY INFECTED.
What do these serologic tests conclude about whether or not this person is / has been affected by Hep B?
They are CHRONICALLY INFECTED.
What is the hepatitis B surface antigen?
HBsAg
A protein on the surface of the hep B virus.
The presence of it indicates acute / chronic infection.
The body usually produces antibodies in repsonse.
The HBsAg is used to make the Hep B Vaccine.
What is the Hepatitis B surface antibody?
anti-HBs
Its presence indicates
a) recovery and hence natural imunity has developed from the Hep B virus OR
b) the person has been vaccinated.
What is the Hepatitis B core antibody?
anti-HBc
Its presence indicates
a) previous OR
b) ongoing infection.
What does a positive result of the IgM antibody to hepatitis B core antigen mean?
IgM anti-HBc
A positive result indicates recent / acute infection.
