please answer all the questions answering only one question is not helpful: 19.
ID: 218058 • Letter: P
Question
please answer all the questions answering only one question is not helpful:
19. there are two possible ligh chains, encoded by two different genes, that can be used to make an antibody.
a. the one most commonly found in Ab molecules is the kappa chain. Why is this?
b. what is the other light chain?
20. for T cells, what is the function of positive slection?
21. using numbers, indicate the correct sequence of occurrence for the following steps in B cells development .
a.___ expression of a functional heavy chain protein
b.___expression of a functional light chain protein
c.___V-DJ recombination
d.___D-J recombination
e.___V-J recombination
f, ___ expression of a functional BCR
22. For each of the HV regions listed below, indicate the mechanism r mechanisms the underlie the varjability of amino acid sequinces that are found there. Your choices are combinatorial, junctional, or both.
A. HV1:
23. CTLA-4 is expressed on a number of different T cells.
a. give an example of a T cell that expresses it.
b. at what stage of the cell’s life cycle will it be expressed (e.g,before or after activation)
c. what is the function of this molecule?
24. clonal selection leads to activation of adaptive T lymphocytes and differentiation into effector cells.
a. where does clonal selection of T cells most commonly occur?
b. where does positive selection of T cells most commonly occur?
25. in secondary lymphoid tissues, after activation and differentiation of a CD+T cell clone the various daughter cells can have different fates.
a. the most common fate is to leave secondary lymphoid tissue as a helper cell, but another type of cell remains in the lymphoid tissue as a non-helper. What type (function) of cell?
b. another fate is to remain in the secondary lymphoid tissue as a helper cell but to migrate out of the T cell area to this other location
c. … as this type of helper cell.
26. compare and contrast clonal selection of T cells with positive slection of T cells with regard to the following.
a. what is the preprogrammed cell fate at the start of each process
(to die unless rescued or to live unless killed)?
for positive selection
ii. For clonal slection
b. what is the phenotype at the start of each process(double positive, single positive, or double negative)?
I. positive selection
ii. clonal selection
28. draw a linear diagram of a TCR B protein (no secanry or tertiary structure)
a. label the N terminus on the legt and the C terminus
b. label the different protein domains
c. within the V domain, label each section that is encoded by different gene segments by letter.
d. label the locations of the different HV regions (CDRs) by number.
e. label the C region domains .
Explanation / Answer
19)Antibodies are composed of Light chain and Heavy chain.
a)Light Chain are of two type:kappa and lambda.
Both are present in different ration in organisms.Mize consist 90% kappa and 10% lambda
Human have 60%kaapa, 40% lambda.
The exact reason of the ratio difference is not known yet but it is assumed that the Vgene rearrangement is reponsible for the specificity of kappa chain in particular organisms.
b)Lambda chain.Slight difference in polypeptide chain sequence between kappa and lambda chain.Immunoglobulin gene for lambda chain is present in chromosome 22 in human with 6 Constant region(Cl).
20)Tcell positive selection.T are lymphocytes a type of white bloos cells reponsible for the cell mediated immunity.They are named as T cells because they mature at thymus.T cell receseptor present on the surface of T cell binds to the antigen on MHC molecules and trigger immune response.
Positive selection-It is a selection process in thymus where mature Tcell are screened to leave thumus and released to the blood.Positive selected Tcells interact with the MHC molecule and expressing MHC Class 1 and class 2 receptor.RAG gene is repressed by positive selected thymocytes resulting in migration of survived and active Tcells to medulla.
21)B cell development
1DJ recombination
2)VJ recombination
3)Expression of functional heavy chain protein
4)VDJ recombination
5)Expression of functional Light chain protein
6)Expression of functional BCR.
23)CTLA-4 Expression
a)Regulatory effector T cell (Tregs) express.
b) It regaulate the activation of Tcells at different stages of immune response known as periferal tolerance.
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