have been posting the same questions and getting no answers ! so please answer a
ID: 206949 • Letter: H
Question
have been posting the same questions and getting no answers ! so please answer all the questions answering only one question is not helpful .
17. how can a professional APC be distinguished from a non-professional APC? In OTHER words, what is the difference ?
18. even though MHC class I and class II proteins are produced in the endoplasmic reticulum, they present peptides derived from proteins that originate in different cellular compartments.
what compartments?
Class I
Class II
19. for the following types of pathogens, indicate which class of MHC will present the majority of its antigens, and explain why.
a. worms
i. MHC class
ii. why
Virus
,MHC Class
why ?
20 . cross presentation is a process that only one type of cell normally does.
what cell?
What is cross presemtation ?
21. if a person was unable to express the HLA-DM protein, how would that impact antigen presentation?
22. limited genetic diversity is a serious issue for endangered species because they are at greater risk of extinction due to infectious disease. What is an immunological mechanism to explain this?
23. regarding a complementarity determining region.
a. what is another term used to describe these regions?
b. what molecules are they found in ?
c. on what cells would you find these structures?
d. what are they complementary to?
24. the antigens in grafted tissue that stimulate rejection in less than twenty days are encoded in what part of the genome?
25. what antibody isotope is found in highest concentration in ..
a. serum
b. feces
26. at least two signal are required to activate both B and T cells so they can differentiate into effector cells.
A. signal 1:
b. signal 2:
27. how is avidity different from affinity?
28. a linear epitope ( determinant) is strucrally different from a conformational epitope. What is the difference?
29. last week, a b cell in your body started producing an IgM ANTIBODY AGAINST AN ANTIGEN IN A vaccine that the university required you to receive. Today, that same B cells starts making an IgGI antibody with exactly the same epitope specificity as in the IgM IT USED TO MAKE. EXPLAIN WHAT CHANGED ABOUT THE ANTIBODY.
Explanation / Answer
17. Professional APCs can efficiently present the antigen to the T cell by internalizing the antigen by endocytosis or phagocytosis, where the antigen is bound to MHC class II molecule. Examples: dendritic cells, macrophages
Non Professional APCs donot inherently express MHC class II proteins. These proteins can be expressed only after stimulation by various cytokines like interferons. Examples of non professional APCs : fibroblasts, thymic epithelial cells, thyroid epithelial cells.
18. Class I: Intracellular (endogenous)
Class II : extracellular (exogenous)
19. a. Worms Class: MHC class II
why: MHC class II present extracellular antigens ie antigens which are present outside the cell. Since worms will present epitopes (part of antigen) outside the cell, MHC class II will present worms to T cells
b Viruses Class: MHC class i
why: MHC I molecules present endogenous (intracellular) antigens. Viruses once infected, become a part of the cell by expressing protein within the cell. Thus becoming intracellular antigens.
20. Cross presentation is done by dendritic cells
Cross presentation is defined as the role of dendritic cells to acquire,process and present extracellular antigens with MHC class I molecules to CD * T cells. This causes CD 8 T cells to get activated. Cross presentation is essential for immunity against tumors and viruses infecting peripheral tissues.
21. If HLA-DM is not expressed in a person, loading and editing of peptides on class II MHC will not be possible, thus disrupting specific peptide presentation to MHC class II molecule.
22. The immunological mechanism to explain endangered species' extinction due to infectious diseases is immune gene variability or variation in the major histocompatibilty complex (MHC).
23. a. Complementarity determining regions (CDRs) are also called idiotypes
b. They are found on immunoglobulins
c. They are found on B cells.
d They are complementary to a specific epitope
24. The antigens are encoded in MHC genes.
25. IgG is found highest in serum
IgA is ofund highest in feces
26. Signal 1: foreign peptide bound to MHC of the surface of an APC
Signal 2: Co-stimulatory proteins like B7 (CD80 and CD86) which recognize co-receptor protein CD28 on the T cell surface.
27. Affinity is defines as the strength of a bond between antibody and antigen. Some isotypes of antibodies can bind to multiple antigens. The overall strength (due to multivalency) is defined as avidity.
28. A linear epitope is linear in sequence with proteins in their primary structure. Thus the antibodies recognize them by its linear sequence.
A conformational epitope has a distinct three-dimensional shape and usually has secondary or tertiary protein structures.
29. This phenomenon is called immunoglobulin class switching where immunoglobulins switch from one class (IgM) to another (IgG) , where the heavy chain changes while the variable region remains the same. Thus the antigen specificity does not change but the immunoglobulin can now interact with various other effector molecules.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.