Which of the following events is not associated with the establishment of allelic exclusion of immunoglobulin heavychain loci? a. active transcription of RAG1 and RAG2 b. degradation of RAG proteins c. expression of only one productively rearranged heavychain locus d. remodeling of chromatin structure of heavy-chain locus so that it resists gene rearrangement e. formation of a functional pre-B-cell receptor.

T-cell receptor diversity is controlled by O b. O c. 1 O d. e. DNA recombination during mitosis in T-cells DNA recombination during prophase of meiosis II DNA recombination during prophase of meiosis l proteasomal degradation of viral proteins proteasomal degradation of host proteins

can ensure that receptors with the same antigen binding sites are found on the surface of each B cell clone. 單選: A. Affinity maturation B. Allelic exclusion C. Negative selection D. Somatic hypermutation E. Positive selection

Suppose you have two A-B-type exotoxins, A-B and A’-B’. A-B binds specifically to all MHC-II cells and blocks vesicle trafficking. A’-B’ binds specifically to all MHC-I cells and stops protein synthesis. a. What would a hybrid toxin, A’-B, do to fibroblast (skin) cells? Provide your rationale. b. What would a hybrid toxin, A-B’, do to fibroblasts? Provide your rationale. c. What would a hybrid toxin, A’-B, do to macrophages? Provide your rationale. d. What would a hybrid toxin, A-B’, do to macrophages? Provide your rationale.