10.3 Matching: During T-dependent antibody responses, numerous receptor/ligand interactions and cytokine signaling events occur between TFH cells and activated B cells. For the following list of surface receptors/ligands and cytokines, indicate whether they are produced by T cells (T), B cells (B), both (TB), or neither (N) in this context.
A. IL-21
B. ICOSL C. CD40L D. CD30L
E. Peptide:MHC II F. CCL21
G. SLAM 10.4 Matching: Match the human disease to the associated genetic defect.
A. X-linked i. Translesion polymerase  lymphoproliferative disorder Polη
B. Hyper IgM type 2 ii. ATM (a DNA-PKcsimmunodeficiency family kinase)
C. Xeroderma pigmentosum iii. SLAM-associated  protein (SAP)
D. Ataxia telangiectasia iv. Activation-induced cytidine deaminase (AID) 10.5 Matching: Indicate whether the following properties apply to IgA, IgD, IgE, IgG, and/or IgM.
A. First produced during humoral response
B. Monomeric (predominantly)
C. Dimeric (predominantly)
D. Pentameric (predominantly)
E. Contains a J chain
F. Capable of eliciting complement deposition
G. Most abundant in mucosal surfaces and secretions
H. Low-affinity
I. Bound onto mast cells
J. Binds to polymeric immunoglobulin receptor (pIgR)
K. Binds the neonatal Fc receptor (FcRn) 10.6 Short Answer: How is TRIM21, a novel class of Fc receptor, different from other Fc receptors?
10.7 Multiple Choice: Which of the following functions is not elicited by antibody binding to Fcγ receptors?
A. Antibody-dependent cell-mediated cytotoxicity (ADCC) via NK cells
B. Phagocytosis by neutrophils
C. Mast-cell degranulation
D. Downregulation of B-cell activity
E. Ingestion of immune complexes by dendritic cells 10.8 Multiple Choice: Which of the following is a false statement?
A. Naive B-cell survival in follicles is dependent on BAFF, which signals through BAFF-R, TACI, and BCMA to induce Bcl-2 expression.
B. Subcapsular sinuses of lymph nodes and marginal sinuses of the spleen are functionally similar areas filled with specialized macrophages that retain but do not digest antigens.
C. ICOS signaling in T cells is essential for their completion of TFH differentiation and expression of the transcription factors Bcl-6 and c-Maf.
D. Both plasmablasts and plasma cells express B7 co-stimulatory molecules, MHC class II molecules, and high levels of B-cell receptors.
E. TFH cells determine the choice of isotype for class switching in T-dependent antibody responses.
10.9 True or False: Germinal centers contain a light and a dark zone. In the light zone, B cells proliferate extensively and are called centroblasts. They are maintained there by CXCL12–CXCR4 chemokine signaling and undergo somatic hypermutation leading to affinity maturation and class switching. In the dark zone, B cells cease proliferation and are called centrocytes. Here, they are maintained by CXCL13–CXCR5 chemokine signaling, express higher levels of B-cell receptor, and interact extensively with TFH cells.
10.10 Multiple Choice: Choose the correct statement:
A. R-loops are structures formed during somatic hypermutation that promote accessibility of the immunoglobulin V regions to AID.