6. The classical pathway of complement activation A) oDepends on lectins B) oReq
ID: 274382 • Letter: 6
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6. The classical pathway of complement activation A) oDepends on lectins B) oRequires antibody bound to a microbe. D) oWorks with free soluble antibody. -C) oUses the alternate pathway 7. Natural killer cells A) Kill cells that lack MHC I B) Kill cells that lack MHC II. O) Kill cells that have MHCI P Are a type of Te cel. s. Injection into rabbits of a A) anti-Fe antibn of pooled human IgG could stimulate production of B) anti-2 chain antibody c) anti-y heavy-chain antibody. D) anti-K chain antibody. E) All are correct. 9. Haptens A) can react with specific antibodies B) cannot stimulate antibody responses without carriers. c) require carrier molecules to be immunogenic D) all of the above. 10. Follicular dendritic cells A) B) C D) Display intact antigen to T cells. Display peptide fragments of antigen to T cells. Display intact antigen to B cells. Display peptide fragments of antigen to B cells. I1. The invariant chain A) Protects MHC II from loading peptides in the phagolysosome. B) Protects MHC I from loading peptides in the endoplasmic reticulum. c) Protects MHC II from proteolysis. D) Protects MHC I from loading peptides in the endoplasmic reticulum. Two protein chains forming a groove that can bind a foreign peptide make up A) MHC II but not MHCI B) Both MHC I and II C) All cytokines. D) MHC I but not MHC II 12.Explanation / Answer
6. The mannose binding pathway of complement activation is initiated by the binding of mannan binding lectin (MBL) to mannose containing carbohydrates present on the surface of bacteria or viruses. The alternate pathway of complement activation is initiated by binding of spontaneously activated complement C3 component to the surface of the pathogen. It is activated by spontaneous C3 hydrolysis.
The classical pathway is initiated by the binding of C1q, to immune complexes via the Fc regions of the antigen-bound immunoglobulins. Hence, it requires antigen-antibody complexes for activation. The antibodies are bound to antigens present on the microbe.
Right answer is B.
7. Natural killer cells (NK cells) are cells that are activated upon encountering cells lacking self-MHC class I molecule. Thus, presence of MHC class I molecules will help them to distinguish between normal and infected cells. NK cells attack cells lacking MHC class I molecules. Thus, viral cells will down regulate MHC class I expression to escape recognition by cytotoxic T lymphocytes. However, such an escape mechanism makes them susceptible to attack by NK cells.
Right answer is A.
8. The rabbit is injected with pooled human IgG. This pooled human IgG will have both K and l light chains. Thus, antibodies will be generated against both these chains. IgG antibodies also have an Fc regions, which will generate antibodies in the rabbit. The heavy chain of the human IgG (gamma) is also recognized as non-self, and will generate antibody production in the rabbit.
Right option is E.
9. Haptens are small molecules cannot initiate an immune response on its own as they are not good immunogens. However, when they are bound to large carrier molecules such as protein that are immunogenic, they elicit production of antibodies. These antibodies can bind to them specifically. Haptens can thus bind to antibodies that re generated specifically against them.
Right answer is D.
10. Follicular dendritic cells are present on the B cell follicles in secondary lymphoid organs. FDCs trap and display native antigens to proliferating B cells. These cells can retain antigens for long periods. The native intact antigens are presented as immune complexes to B cells and are important in humoral immune responses.
Right answer is C.
11. The invariant chain is required for the association of alpha and beta chain of class II MHC molecules in the endoplasmic reticulum. The invariant chain trimerizes in the ER and associates with class II MHC molecules. It is released from ER in a nine subunit complex. The MHC invariant chain complex moves out of the rough endoplasmic complex into Golgi. The invariant chain protects class II from binding intact polypeptides in the endoplasmic reticulum. The MHC class I molecules can load peptides imported from cytosol in ER. The invariant chain allows the class II molecules to be targeted to specialized endosomes. Class II MHC bind peptides in endosome prior to cell surface expression.
Right answer is D.
As per Chegg’s rules, only one answer needs to be answered.
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