0. All of the following are needed for somatic recombination except: a. cytokine
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0. All of the following are needed for somatic recombination except: a. cytokines 0. recombination signal sequences c. repair enzymes d. recombinant activating genes 11. Developing B cells have which receptors on their surfaces a. IgM and IgG b. IgM and IgD c. IgM and IgA d. IgD and IgG 12. Which cell type has no MHC molecules? a. dendrites b. red blood cells c. respiratory cells d. white blood cells 3. Why is it necessary for the formed B cell receptor (BCR) to complex with the 2 transmembrane proteins, Ig-alpha and Ig-beta, before leaving the ER to go to the surface theBCR would be destroyed by cytoplas b. mic enzymes if it moved on its owrn a· BCR without alpha and beta turns the cell into a giant macrophage the alpha and beta tails are long enough to signal the B cells to divide, the BCR tails aren't d. c. the alpha and beta proteins help bind the antigen to the BCR 14. Which is not true about immunoglobulin receptors (lg) and antibodies (Ab)? a. Ig is made in B cells, Ab in T cells b. Ig is bound to the cell membrane, Ab found in extracellular fluid (ECF) c. Ig binds Ag (antigen) to stimulate B cell differentiation, Ab binds Ag and leads to Ag destruction d. Ig has a transmembrane protein tail; Ab does not 15. B cell receptor diversity is brought about by (circle 2) a. somatic hypermutation b. cross presentation c. isotype switching d. somatic recombinationExplanation / Answer
10. ans is Repair enzymes
Isotype switching increases the functional diversity of antibody molecules. It occurs following antigen stimulation and Th2 cytokine production. V(D)J recombinase expressed in developing B cells recognizes recombination signal sequences (RSS) of nine (nonamer) and seven (heptamer) base pairs flanking each Ig gene segment. Products of at least two recombination-activating genes, RAG-1 and RAG-2, plus enzymes to ligate (reattach) the DNA and terminal deoxynucleotidyl transferase (TdT) are required for somatic recombination.
11. IgM and IgD
IgM is always the first class of antibody made by a developing B cell. After leaving the bone marrow, the cell starts to produce cell-surface IgD molecules as well, with the same antigen-binding site as the IgM molecules.
12. RBC
MHC-I is usually found in all nucleated cells. MHC-II is found on the surface of antigen presenting cells such as dendritic cells, macrophages and B-cells. RBC has no nucleus and no MHC on the surface.
13. The alpha and beta proteins help bind the antigen to the BCR. The role of the Ig alpha /Ig beta Heterodimer is in the internalization and intracellular transport of the B Cell Antigen Receptor.
14. Statement a is wrong.
Antibodies are produced by specialized white blood cells called B lymphocytes (or B cells). When an antigen binds to the B-cell surface, it stimulates the B cell to divide and mature into a group of identical cells called a clone. The mature B cells, called plasma cells, secrete millions of antibodies into the bloodstream and lymphatic system.
15. Somatic recombination
The somatic recombination process for generating antibody and TCR diversity is unique among mammalian systems. Isotype switching increases the functional diversity of antibody molecules.
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