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
