Immunology 146:474

1. Immunology 146:474 • Tu, Fri 1st period (8:40-10:00 AM) • Serc 118 • Dr. Lori Covey-Office hrs: 1-3 Thursday • Dept. of Cell Biology & Neuroscience Nelson Hall, B314 • covey@biology.rutgers.edu • Class web site: http://lifesci.rutgers.edu/~covey/Immuno/index.htm

2. MHC Class I structure

3. MHC Class I structure b-pleated sheet b-pleated sheet

4. Structure of MHC class II molecules

5. MHC Class II structure, cont’d

6. MHC I/peptide MHC II/peptide

7. Figure 3-23 NH2 terminus NH2 terminus COOH terminus

8. Peptides eluted from two different MHC class I molecules Green residues are the anchor residues, Y=tyrosine, F=phenylalanine, both aromatic amino acids

9. Presentation of peptide bound by MHC class II

10. Peptides that bind MHC class II molecules are variable in length Peptides are at least 13 amino acids long and can be longer

11. Figure 3-21 part 2 of 3

12. T cell receptor binding to peptide:MHC class I

13. Figure 3-10

14. Figure 3-14

15. Specificity of a T cell receptor is defined both by the peptide it recognizes and by the MHC molecule bound to it

16. Figure 5-17

17. Figure 1-24 part 1 of 3

18. Figure 1-24 part 2 of 3 Fc receptors

19. Figure 1-24 part 3 of 3

20. Figure 1-15 Macfarlane Burnet theory of clonal selection-1950s

21. Mature B cells display membrane-bound Immunoglobulin (antibody) molecules, which serve as receptors for antigen. Each molecule of Ab on the membrane of a single B cell has an identical binding site for antigen. Bone marrow, pre-B cells

22. Interaction between antigen and the membrane-bound antibody (mIg), as well as interactions with T cells and macrophages, selectively induces the activation and differentiation of B-cell clones of corresponding specificity. Selected B cells divide repeatedly and differentiate over a 4-5 day period generating a pool of plasma cells (terminally differentiated) and memory cells. 2o lymphoid organs Germinal centers

23. To activate a B cell, it needs to receive a signal from antigen recognition through the mIg and a signal from CD4+ T cells

24. Figure 1-20

25. Mature B cells display membrane-bound Immunoglobulin (antibody) molecules, which serve as receptors for antigen. Each molecule of Ab on the membrane of a single B cell has an identical binding site for antigen. Bone marrow, pre-B cells

26. Mechanisms for generating diversity Number of total number of antibody specificities available to an individual is known as the antibody repertoire Ig genes are rearranged in antibody-producing cells Process called “Somatic recombination”

27. A single B cell gives rise to a single antibody molecule with two identical heavy and two identical light chains A resting, naïve B cell expresses IgM and IgD on its surface as its BCR (B cell receptor).

28. Southern blot analysis of V region and C region. Digest DNA with restriction enzyme and separate pieces of DNA in an electrical field. Fragment of DNA Labeled RNA representing Bence-Jones Protein (light chains) Hybridized to DNA isolated From either fibroblasts or B cells

29. Organization of the Human Heavy chain variable region loci VH region The Variable region of the Ig heavy chain is encoded by three Gene segments; The V segment 95-101 amino acids The D segment 2-5 amino acids The J segment up to 13 amino acids

30. VH region

31. Organization of the Light Chain Loci The Variable region of the Ig light chain is encoded by two Gene segments; The V segment 95-101 amino acids The J segment up to 13 amino acids

32. Figure 4-4

33. Figure 4-3 The heavy and light chain genes are located on autosomes so there are 2 copies of the heavy chain locus, 2 copies of the  light chain and  light chain loci Possibility of generating 1011 antigen specificities

34. First mechanism that generates diversity Combinatorial Diversity Any functional VH segment can recombine with any DH segment and any JH segment Any functional VL segment can recombine with any JL segment

35. Somatic recombination at the Ig heavy chain locus

36. D-->J rearrangements on both alleles VH DH JH C V-->DJ rearrangement VHDJH C

37. Figure 3-6 Framework and hypervariable regions define the Variable Regions of the Ig heavy and light chain polypeptides

38. 12/23 7-mer 9-mer Recombination Recognition Sequences (RSS) Only RSS elements that have different spacer lengths can recombine with each other

39. 12 or 23 7-mer 9-mer Recombination Recognition Sequences (RSS) Only RSS elements that have different spacer lengths can recombine with each other

40. Figure 4-6 part 1 of 2

41. Figure 4-6 part 2 of 2

42. Figure 4-7 Proteins required for carrying out recombination called “V(D)J recombinase RAG I and II enzymes required For variable region Somatic recombination Create hairpins Which are cleaved. Terminal deoxynucleotidyl transferase (TdT) are added, nt can be subtracted as well by nucleases

43. Figure 4-7 part 3 of 3 2nd mechanism for creating diversity: Junctional Diversity Enzymatic processes creates Diversity in the joint between gene segments

44. Figure 4-8 part 1 of 3 Creates tremendous diversity at the joins of the three segments

45. Figure 4-8 part 2 of 3

46. Figure 4-8 part 3 of 3

47. Figure 4-7 part 3 of 3 3rd mechanism for creating diversity: Combinatorial- at the heavy and light chain level Pairing of individual heavy chains with different light chains

48. Somatic hypermutations create diversity • Occurs later after B cells are in secondary lymphoid organs • Introduces single nt mutations into germline DNA • Results in increased binding affinity of antibody for antigen

49. 4th mechanism for creating diversity: Somatic hypermutation Occurs after stimulation with antigen in the antigen-dependent stage of B cell differentiation Introduces point mutations into the V regions of the rearranged heavy- and light-chain genes at a very high rate Requires a signal from CD4+ T cells

50. Somatic hypermutations create diversity