Midterm Part 4 Flashcards
What is are the 3 signals needed to activate T cells?
1: Antigen specificity: MHC/peptide TCR
- When it’s the right match, leads to CD3-mediated signalling to nucleus
2: co-stimulation B7 (CD80/CD86)/CD28: Necessary for full T cell activation
• clonal proliferation
• acquisition of effector function
3: cytokines
- DC’s produce IL-12, IL-18
- IL-12, IL-18 influence T cell function (both CD4 and CD8)
What is the result of signal 1 and 2 in activating T cell?
- IL-2 production of clonal proliferation
- Up-regulation of CD40L
What happens if a Th cell is instructed to produce IFNy?
It will lead to activation of macrophages
What are the effector molecules of a CD4 T cell? What is the function of a CD4 T cell?
- CD40L, IL-2, IFNy
- to help macrophages, B cells and CD8 T cells
What is the result of IL-2 production?
Clonal proliferation
What is the result of IL-12 and IL-18 production from the DC?
T cells will perform the effector function
What are the five important features of the adaptive immune system?
- Diversity
- Specificity
- Inducibility
- Memory
- Self-tolerance
What is the structure of a BCR?
Mlg: membrane bound immunoglobulin for antigen binding
Iga and Igb:m signalling partners
What kind of Ig does an immature B cell express?
IgM+
What kind of Ig does a naive, mature B cell express?
IgM+ and IgD+
How do B cells undergo negative selection? What is the purpose of this?
- Any BCR that recognizes self-antigens in the bone marrow is deleted
- to eliminate potentially self reactive B cells
What is the role of the BCR?
BCR is responsible for antigen binding and determines the antigen specificity of the B cell
Where does the B cell begin to express the BCR and costimulatory proteins?
In the bone marrow
What is the Igα/Igβ subunit analogous to in the T cell?
CD3
What will happen if a BCR binds to an antigen while still in the bone marrow?
the Igα/Igβ subunit will send signals for it to die (clonal deletion)
Why do B cells not need to go through positive selection?
They don’t need to interact with MHC like the T cell does
Where do B cells go once they have matured?
The spleen and the lymph nodes
What is the structure of a BCR?
2 identical heavy (H) chains and 2 identical light (L) chains. Each of the immunoglobulin H and L chains has one V region (V = variable) and one C region (C = constant). The VH (variable region of the Heavy chain) and VL (variable region of the Light chain) regions combine to form an antigen-binding pocket. There are two antigen-binding sites per BCR (or immunoglobulin molecule)
What is the name for immunity due to antibodies?
Humoral immunity
What is the difference between mlgs and slgs?
The amino acid sequences at the carboxyl-terminus of the H chain.
- For mIg, the amino acids are hydrophobic so that the polypeptide is anchored in the membrane when the vesicle fuses with the plasma membrane.
- For sIg, the amino acids tend to be hydrophilic so that when the vesicles with the plasma membrane, the antibodies are released into the extracellular fluids
True or false: BCR’s exist on B cells, but not plasma cells or T cells
True
Can T cells recognize tertiary epitopes? Why or why not?
T cells can only recognize linear sequences, and this is because of the MHC complex
- it is limited to binding in the MHC binding cleft (unlike BCR, which can bind to soluble antigen)
What roles do antibodies play in immunity? What determines which role an antibody will play?
- Neutralization
- Opsonization
- Complement activation
The constant region of the heavy chain
What are the five types of Ig’s?
IgM, IgD, IgG, IgA, IgE
When a mature B cell is not activated, what is it doing?
Circulating through blood, lymph, and lymph organs
What are the two signals that B cells need to be activated? What is the third signal?
- Antigen recognition
- B cell recognizes Ag, cross linking occurs, clusters of Iga/IgB form
- B cell internalizes the Ag and presents it on MHC II
- Costimulation from the T cell
- an ACTIVATED T cell binds to the MHC II peptide complex
- CD40L on T cell joins CD40 on B cell
1+2= proliferation and effector function
- cytokines: class switching
What is the purpose of the hyper variable region on the antibody?
contributes significantly to the antigen-binding site and are the part of the antibody that contacts the antigen
The constant regions on the H and L chains are _______ specific
Specific
