L2 - Introduction to immunobiology Flashcards
Key cells involved in the innate immune response
Phagocytes, NK cells
Key cell types in adaptive immune response
T and B lymphocytes
How are T cells subcategorised
CD4+ (helper) CD8+ (cytotoxic)
Non-specific recognition and acquisition of memory are both features of the adaptive immune response. True of false?
False - SPECIFIC recognition and acquisition of memory are features of ADAPTIVE, while NON-SPECIFIC recognition and no generation of memory ae features of INNATE response.
Ion chelators reduce bacterial growth and interferons are antiviral cytokines associated with the innate response, name 3 other parts of the innate response.
Physical barriers, complement cascade (alternative pathway - triggered by pathogens), secreted components (antimicrobial peptides), proteolytic enzymes (cope with bacterial and fungal infections).
How long is the lag phase before the primary response is seen?
5-6 days
What interaction and process is required for Ig to be made in the primary response?
- Interaction between B and T cells. 2. Clonal expansion.
How does the secondary response curve compare with the first?
It is more rapid and higher magnitude than the primary response.
The secondary response demonstrates _______specificity.
High specificity.
All the cells of the blood arise from _________?
A common pluripotent hematopoietic stem cell.
Define pluripotent
Capable of giving rise to a several different cell types.
From which progenitor do immature dendritic cells arise?
Either common myeloid or common lymphoid.
What happens to a megakaryocyte for it to give rise to platelets?
It fragments.
What happens to an erythroblast to become an erythrocyte?
It sheds its nucleus.
What form and state are immature dendritic cells when they are in the tissue?
Resting state and immature form.
Once activated, where do immature dendritic cells go to become mature?
Lymph nodes.
What is the main role of immature dendritic cells?
To present antigen to T cells.
What are the most effective antigen presenting cells?
Dendritic cells.
Where does antigen uptake occur regarding dendritic cells?
In peripheral sites.
What are the two main roles of macrophages?
Phagocytosis and degradation which allows for antigen presentation to activate T cells.
Are neutrophils effective APCs?
No, but they are highly phagocytic.
What types of infection to neutrophils mainly protect against?
Fungal and bacterial infections.
Which cell type is good at killing parasites too large to be engulfed by a cell eg. worms?
Eosinophils.
Which cell type is responsible for allergic responses and anti-parasitic immunity.
Mast cells
Which cell type releases histamine and other active agents which act on/dilate blood vessels to allow cells from circulation into the tissues?
Mast cells.
Where do B cells mature?
Bone marrow.
Which cells secrete antibodies?
Plasma cells
How many chains make up an antibody?
4 (2 identical light and 2 identical heavy)
Because antibodies have 2 antigen binding sites, they are called _____?
Bivalent.
What links the two heavy chains together?
Disulphide bridge
What do the turns at the end of the beta-pleated sheet contribute to?
Antigen binding
Which part of the antibody is responsible for effector function.
Fc (constant region)
What are the Fab portions for?
Antigen binding
What is the name of the protease which can cleave an antibody into 3 fragments?
Papain
List the 3 main effector functions achieved by antibodies.
Neutralization of toxins/virus particles, opsonisation, complement activation.
Which of neutralization, opsonisation, complement activation result in degradation and presentation of peptide components to T cells?
All 3
What is a main difference between opsonisation and neutralization ?
Opsonization can happen to whole microbes whereas neutralization happens to individual protein molucules.
Complement activation occurs when bacteria is found where?
In the plasma (systemic infection).
Which part of the antibody do complement components bind to?
The Fc portion, but only following the binding of the Fab portions to bacteria causing a slight change in conformation.
Describe how T cells arise.
Pluripotent haematopoietic stem cell differentiates into a common lymphoid progenitor in the bone marrow. This then migrates to the thymus where T cells mature.
What do T cell receptors recognise?
foreign antigen fragments called human leukocyte antigens (HLAs)
List the 3 main roles of T cells
- Help B cells make antibodies, 2. Promote bactericidal activity of macrophages, 3. Cytolysis of infected cells (CD8+ T cells)
Which co-receptor do T helper cells recognise and which class of HLA do they recognise. Also what is their function.
Th cells express CD4 co-receptor, recognise class 2 HLAs and activate macrophages, help B cells and releasing cytokines.
Which T cell subset causes the lysis of infected and tumour cell.
T cytotoxic (Tc) cells express CD8 and recognise class 1 HLAs causing lysis.
Compare the ways in which the professional antigen presenting cells take up material.
Dendritic cells - phagocytosis or pinocytosis. Macrophages - phagocytosis. B cells - receptor mediated endocytosis (using the BCR)
Which class of MHC molecules is stabilised by a beta2- microglobulin and what are its other components?
MHC class 1 is composed of an alpha chain with 3 domains and one membrane spanning region. It is stabilised by the beta2- microglobulin.
Describe the structure of MHC class 2 molecules.
1 alpha and 1 beta chains, each with 2 domains and each with a membrane spanning region.
How is the peptide fragment presented to T cells?
The peptide fragment is internalised, processed and presented on the cell surface as an HLA.
What is the difference between the recognition specificities of TCRs and BCRs?
BCRs and antibodies can recognise the native antigen whereas TCRs can only recognise a fragment of antigen (presented by MHC molecule) so it must be unfolded and cleaved by proteases.
List the primary and secondary lymphoid organs.
Primary - thymus and bone marrow. Secondary - lymph nodes, spleen, mucosal associated lymphoid tissues eg. Peyer’s Patches, urogenital tract, tonsils and adenoids.
What is the difference in purpose between the primary and secondary lymphoid tissues?
Primary - sites of lymphoid (B and T cell) development. Secondary - sites of lymphocyte interaction with antigen, other lymphocytes and accessory cells.
What is the role of the lymphatic system?
Lymph (which may contain antigens) from interstitial spaces drains into the lymphatic vessels which carries it to lymph nodes. Lymphocytes and lymph return to the blood via the thoracic duct and then re-joins the circulation via the left subclavian vein.
What are the sites of B cell differentiation (helped by Th cells) within lymph nodes?
Germinal centres
How does lymph enter a lymph node?
The afferent lymphatic vessel. (Exits via the efferent lymphatic vessel)
What kind of cells do the medullary chords within lymph nodes contain?
Macrophages and plasma cell.
