Immunology Chapter 5, Lecture 1

1. ImmunologyChapter 5, Lecture 1 • Richard L. Myers, Ph.D. • Department of Biology • Southwest Missouri State • Temple Hall 227 • Telephone: 417-836-5307 • Email: rlm967f@mail.smsu.edu

2. Basic structure of Ab • Antibodies (Ab) are found in the serum • Four fractions seen after electrophoresis (Tiselius and Kabat): • albumin • alpha (a) • beta (b) • gamma (g) • After reaction of hyperimmune serum with antigen, the gamma fraction is reduced

4. Experiments to show Ig structure • Porter • used brief papain digestion to produce fragments • produced two identical fragments • called Fab because they bound antigen • MW of 45, 000 • produced a larger fragment • called Fc because it could be crystallized • MW of 50,000

7. Experiments (cont) • Edelman • reduced the interchain disulfide bonds with ethanol and alkylation • followed by gel filtration • produced two peaks • Peak I contained the 50,000 MW heavy chain • Peak II contained the 25,000 MW light chain

9. Fine structure of Ig • Bence-Jones provided early information about Ig structure • Light chain structure • variable (V) region • constant (C) region • contains kappa (k) or lambda (l) markers • 60% kappa, 40% lambda in humans • a single ab molecule expresses only one of these

10. Fine structure (cont) • Heavy chain • contains a variable (V) region • also contains a constant (C) region • can be designated as m, g, a, d or e • each represents a different class of Ab • Domains of heavy and light chains interact to specifically bind antigen and play some effector roles

13. Variable region domains • Amino acid composition of VH and VL gives information about Ab specificity • Sequence variability is concentrated in hypervariable regions • Three hypervariable regions found in both heavy and light chain • Form the basis for antibody specificity • Complementarity-determining regions

16. IgG animation

17. Assignment • Read Chapter 5, Immunoglobulins: Structure and Function • Review question 2 (pg 141)