Which of the following describes thymus-independent (TI) antigens?

A) They induce long-term immunological memory.
B) They induce a late antibody response that is predominantly IgG.
C) They contain repetitive epitopes on the surface of microorganisms.
D) They induce high-affinity antibodies through somatic hypermutation.
E) All of the above are correct.

21. A primary focus forms after a circulating naive B cell forms a conjugate pair with a T cell in the lymph node.

A) Medullary cords
B) TH1 cell in the B-cell zone
C) Cytotoxic T-cell in the T-cell zone
D) Follicular dendritic cell in the germinal center
E) TFH cell in the germinal center

22. Isotype switching in activated B-cells requires binding of MHC II on the B-cell with the T-cell receptor plus binding of:

A) B7 and CTLA4
B) CD40 and B7
C) CD40 and CD40L
D) CR2 and CTLA4
E) B7 and CD40L

23. In which of the following processes do Fc receptors play a role?

A) Opsonization
B) Deposition of complement
C) Antibody-dependent cell cytotoxicity
D) Priming of mast cells
E) All of the above are correct.

24. The process that drives an increase in antibody affinity for antigen is known as:

A) Apoptosis
B) Affinity maturation
C) Antibody-dependent cell-mediated cytotoxicity
D) Opsonization
E) Clonal expansion

25. The specific isotype/class antibodies switch to during B-cell activation relies on:

A) RAG1
B) TOT
C) Cytokines produced by TFH cells
D) B7 binding to CD28
E) Cytokines produced by stromal cells