Lumphocyte Receptors and B-Lymphocytes Flashcards
What cells are the major components of the adaptive immune system?
Lymphocytes!
What are the X2 board types of lymphocyte?
T-cells or lymphocytes
B-cells or lymphocytes
What is the structure of the T-cell receptor?
It is a heterodimer (X2 different chains)
= X1 alpha chain
= X2 beta chains
Each chain consists of a long constant region with a small tip called a variable region, the variable region being the antigen binding site.
What is the structure of the B-cell receptor?
It has X2 antigen binding sites as it is a Y-shaped structure comprised of:
= X2 heavy chains (long inside chains)
= X2 light chains (inner shorter chains)
Again the variable regions are found at the tip.
What is the main concept of adaptive immunity in terms of the number of cells with the specific receptor for that antigen?
When first in contact with an antigen, the cells divide to create larger pools of these cells in order to fight it. These remain as memory cells therefore if the same antigen is present again the number of quiescent memory cells allows for the antigen to be dealt with more rapidly next time.
What are the rough timings for the:
1) First exposure
2) Second exposure
1) 12 days
2) 5-7 days
What is the name of the process used by the body to ensure receptor diversity is achieved?
gene rearrangement
What X3 subdivisions make up the variable region of an antibody heavy chain of a B-cell split into?
What X2 subdivisions make up the variable region of an antibody light chain of a B-cell split into?
Heavy chain = variable, diversity and joining
Light chain = variable and joining (no diversity)
What are the X2 subdivisions of gene rearrangement?
1) combinatorial diversity (the random variations of possible combinations)
2) joining diversity (adding or removing extra nucleotides at the sections where the sections of the chains join)
Where are B-cells developed and where do they undergo gene rearrangement?
In the bone marrow (B for Bone)
Where are T-cells developed and where do they undergo gene rearrangement?
In the thymus (T for Thymus)
What happens when antigens bind to T-cell receptors?
They can become cytotoxic or helper T-cells.
What happens when antigens bind to B-cell receptors?
They differentiate to form plasma cells which produce antibodies of the same specificity as that on the B-cell for which they came.
What is another name for an antibody?
Immunoglobulin (Ig)
Which cells produce immunoglobulins?
Plasma cells (which are differentiated B-cells)
What X2 Greek letters can the antibody light chain be?
Kappa or lambda
What type of bonds connect the immunoglobulin heavy chains together and also the heavy chains to light chains?
Disulphide bonds.
Which Ig is found mostly in the serum?
Igg
Which Ig is found mostly in mast cells?
Which cells are Ige mediated and linked to histamine release?
Ige
Mast cells (basophils)
What are the X5 classes of Ig?
M A D G E
Which region of the Ig determines its class (MADGE)?
The constant region
What is the name given to the paired constant regions of immunoglobulins?
The Fc region.
What links opponisation and the Fc region of antibodies?
Once oponised, phagocytic cells can recognise these molecules and bind to the Fc region of the attaches antibodies via Fc receptors to phagocytosis and kill them.
What does it mean when antibodies agglutinate participles?
As they can bind X2 antigens, they can cross link them and ‘agglutinate’ them to disarm them.
Which X2 classes of Ig ‘fix’ complement?
M and G
What is the main role of serum Igg?
Opsonisation of pathogens for NK killer cells.
What are the subclasses of Igg?
What is their abundance in the blood?
Ig1 (most abundant) —> Ig4 (least abundant)
Is Iga round in the serum?
Only as a monomer although it can form a dimer (dimeric Iga)
What chain joins X2 Iga molecules to form dimeric Iga?
A J chain
What is the main role of Iga?
It works on mucosal surfaces, is transported into the gut lumen and agglutinates gut bacteria to regulate their population.
What receptors does Iga combine with to cross the mucous membrane into the lumen?
Secretory component.
What structure is Igm?
Pentameric (= X5 molecules)
What is the term given to describe the strength of a bond between an antibody and an antigen?
Avidity?
What is Igm good for?
Agglutination due to X10 possible binding sites for antigens.
Which X2 classes of immunoglobulin are expressed on newly formed B-cells?
Igm and Igd
What process, which can only occur in B-cells, involves the cell improving its specificity for a specific antigen?
Affinity maturation.
Where a lymphocytes found/how do they move around the body?
They are CONSTANTLY circulating around the blood and lymphoid tissue to increase their chance of encountering the antigen for which they are specific to.
What is the difference between primary and secondary lymphoid tissues?
Primary = wheee lymphocytes are formed
Secondary = where they are activated
What are the names of the zones found in secondary lymphoid tissue where B-cells are found to be dividing?
Terminal centres
Name some secondary lymphoid tissues?
Lymph nodes
Spleen
Tonsils
Peters patches (small intestine wall)
What happens to B-cells regarding the terminal centres when they encounter their specific antigen?
They enter the terminal centres and divide rapidly.
As B-cells divide in the germinal centres, how does affinity maturation occur?
As they divide they somatically hypermutate their immunoglobulin variable regions and select those daughter cells with the immunoglobulins that have highest affinity for the antigen in question.
Therefore affinity maturation = somatic hypermutation followed by selection.
What else can B-cells do to their immunoglobulins within the terminal centres?
They can class switch.
This means keeping the same variable regions but switch classes of Ig from Igm and Igd to produce the Ig’s needed for different functions.
What X2 classes of cells leave the germinal centres?
1) plasma cells which move to the bone marrow to make Igg or to the intestine to make Iga.
2) affinity matured quiescent memory B-cells.
What are monoclonal antobodies?
Identical antibodies which are all clones of a single parent cell.
What are chimeric antibodies?
They are mouse derived variable regions on human constant regions.
What suffix do chimeric antibodies have?
-ximab
Chimeric antobodies can be made even more human, what is the suffix of humanised antobodies?
-zumab
Monoclonal antobidies can be fully human, what is the suffix of human monoclonal antobidies?
-umab
What does adalimumab do?
It binds to TNF alpha to treat inflammatory diseases.
What does it mean to be A positive in blood type or rhesus positive?
It means you display the A and rhesus antigen on your RBC surface.
