B-II Adaptive immunity Flashcards
What is the primary function of B cells in adaptive immunity?
Produce antibodies
B cell response is referred to as humoral immunity.
How are T cells and B cells connected in the immune response?
T-cells and B-cells interact, with T-cells activating B-cells and triggering isotype switching and affinity maturation. B-cells can also act as antigen-presenting cells to activate naive T-cells
What is the role of CD4+ helper T-cells?
Produce cytokines to activate macrophages and stimulate inflammation
CD4+ T-cells require antigen-presenting cells (APCs) for activation.
What does the B-cell receptor (BCR) resemble?
An antibody
BCR is a membrane-bound form of antibody.
What is the importance of IL-7 in lymphocyte development?
It is an important growth factor
IL-7 is crucial for the development and survival of B and T lymphocytes.
What is the function of chemokines in lymphocyte migration?
Attract lymphocytes to specific areas
Chemokines interact with receptors on lymphocytes to guide them to lymph nodes.
What are the components of the T-cell receptor (TCR)?
one α and one β chain
TCR consists of one alpha and one beta chain.
What is the role of the high endothelial venule (HEV) in lymphocyte trafficking?
Allows naïve lymphocytes to migrate into lymph nodes
HEVs have specific ligands that slow down lymphocytes for entry.
What is the structure of an antibody?
2 heavy chains and 2 light chains
Antibodies have a variable region for antigen binding and a constant region.
What is affinity maturation?
Increased affinity to antigen through somatic hypermutations
Affinity maturation occurs in germinal centers when B-cells interact with T-cells.
What is isotype switching in B cells?
Change of antibody type without changing affinity
Triggered by T-cell cytokines, B-cells can switch from IgM to other isotypes.
What are the functions of IgG antibodies?
Bind antigens, activate complement, stimulate ADCC
IgG is the most abundant antibody in humans and plays a key role in immune responses.
True or False: CD8+ T-cells recognize MHC Class II presenting antigens.
False
CD8+ T-cells recognize MHC Class I presenting antigens.
Fill in the blank: The _______ is a secondary lymphoid structure in the gut.
Peyer’s patch
Peyer’s patches are important for gut immunity.
What are some of the functions of antibodies in the immune system?
Neutralization and opsonization of pathogens
Antibodies bind to antigens, making them harmless and marking them for destruction.
What is the difference between affinity and avidity?
Affinity is the strength of binding at a single site, while avidity is the overall strength of binding considering multiple sites
Avidity reflects the total strength of interactions between multivalent antibodies and antigens.
What triggers the activation of CD4+ T-cells?
Presentation of antigen by MHC Class II on APCs
This interaction stabilizes the binding of TCR and MHC Class II.
What is the main role of memory T-cells?
To provide long-lasting immunity
Memory T-cells can quickly respond to previously encountered antigens.
What is the function of the Fc region of an antibody?
Activate complement system and bind to Fc-receptors on immune cells
The Fc region is critical for mediating immune responses.
Which BCR is expressed by naive B-cells?
IgM and IgD
Where does the T and B lymphocyte mature, respectively?
The T-lymphocyte moves to the thymus, while the B-lymphocytes stays in the bone marrow
Name three receptors T-cells need to express to be transported to the lymph nodes?
L-selectin, CCR7, LFA-1
What does L-selectin do?
The ligand is found on the HEV, which allows the T-cells to adhere to the walls and “stop” by the lymph nodes
What does CCR7 do?
Chemokine receptor, recognize chemokines and activates migration to the T-cell zones in lymph nodes. It also activates expression of LFA-1 receptor
What does LFA-1 do?
Binds to HEV more stably, so that the T-cells fully stop and can move into the lymph node
What is the B-cell zone of the lymph node?
Follicles
What is the secondary follicles also called?
Germinal centers
What happens to the follicles when B-cells get activated in the lymph nodes
They form the germinal centers
What is the T-cell zone of the lymph node?
Paracortex
Fibroblast reticular cells (FCRs)
Forms a structure to ensure DCs meet a lot of T-cells
How does the IL-2R change in activated cells?
Activated T-cells have a fully expressed IL-2R, with three chains, which has a much higher affinity for IL-2
What does IL-2 do?
A proliferation signal that causes clonal expansion of activated T-cells
True or false? One CD4+ clone can produce different cytokines.
TRUE
True or false? One B-cell can produce different antibodies
FALSE
True or false? One B-cell can produce different classes of antibodies
TRUE
True or false? One plasma cell can produce different classes of antibodies?
FALSE
What is opsonization?
When antibodies or complement proteins bind to antigens and makes it easier for phagocytosis by phagocytes
What is neutralization?
When antibodies or complement proteins physically stop the antigen from attach to or infect the body cells
What triggers affinity maturation and isotype switching?
T-cells
What are some differences between BCR/Abs, TCR and MHCs?
TCRs and MHCs only recognize linear peptides, while BCRs can recognize peptides, lipids, polysaccharides, etc. BCRs can also recognize conformational determinants
What is the function of the hinge in antibodies?
To make them more flexible, to attach to epitopes closer or further away. Also make the Fc regions more accessible for receptor binding
Which antibody classes lack hinges?
IgE, IgM
Which antibody classes form multimers?
IgM, IgA
Which antibody classes have subclasses (in humans)?
IgG (1-4), IgA (1-2)
Which antibody classes activate the compliment system?
IgM, IgG
Which Fc receptor is inhibatory?
Fc-gamma-RIIb
What is ADCC?
Antibody-dependent cell-mediated cytotoxicity. IgG binding to surface antigens, reqruiting NK cells or macrophages with Fc-gamma-RIII.
Which antibodies have a J-chain?
IgM, IgA
IgG
The most abundant antibody. Four subclasses in humans. Has hinge region. Three Fc regions. Neonatal immunity, can be transferred from mother to fetus. 23 day half life. Can activate compliment
IgE
Lack hinge. Four Fc regions. Very potent, involved in allergic reactions. 2 day half life.
IgD
Naive BCR. 3 day half life. None in serum. Three Fc regions.
IgA
Has J chain. Found in mucosa, three Fc regions. Six days half life.
IgM
Has J-chain. Naive BCR. Can activate complement. 5 day half life. Four Fc regions. Lack hinge.
