Chapter 1 Answers to self-check questions

1.1 What are the differences between a primary and secondary immune antibody response?

Primary immune response involves predominantly IgM, secondary IgG and is larger in terms of the amounts of antibody produced.

1.2 What are the functions of antibody molecules? See Figures 1.4 and 1.5.

To bind antigen and elicit its removal or attack by other immune cells and/or complement activation. The Fab fragment contains the antibody paratope which binds antigen, the Fc portion is the domain which binds complement and other cellular receptors on immune cells.

1.3 How does complement bring about red cell destruction?

C1 components of complement bind to the Fc portions of IgM and some IgG molecules to initiate the complement cascade. This results in the membrane attack complex (MAC) which is able to disintegrate the red cell.

1.4 What methods can be used to detect IgG antibodies?

Agglutination of red cells (direct detection, or via spun columns) , the indirect anti-globulin test (using anti-human IgG as some IgG do not directly agglutinate red cells); enzyme treatment of red cells to enhance agglutination; addition of macromolecules to enhance agglutination. See chapter 2 for methods to detect clinically significant antibodies in haemolytic disease of the newborn and fetus and chapter 9 for methods to detect anti-HLA antibodies in transplantation science