Both the kappa and lambda light chain genes contain each V and J segments, but not D segments.TrueThe heavy chain VDJ assembly is completed before the light chain VJ assembly starts. Both events are separated by rounds of cell division, during which B cells that have a functional heavy chain make a clone of 100 cells of themselves.TrueA surrogate light chain is fitted to the newly made heavy chain to test if the heavy chain can bind to a light chain. If it does, a signal is sent into the nucleus, saying that no further heavy chain rearrangements should be made.TruePro-B cells come first, then pre-B cells. In pro B cells, VDJ segments are arranged, while in pre-B cells, only VJ arrangements are made.TrueOut-of-reading-frame VJ arrangements can be repaired when making light chains, until no more V and J cassettes are left. When making light chain arrangements, two kappa and two lambda gene copies can be used. Kappa genes are used before lambda genes.TrueThe first checkpoint during B cell development (in Phase 1 inside the bone marrow) is if a functional light chain is made. After that, a second checkpoint tests for a functional heavy chain.False20% of all B cells, just after they assembled their receptors, are self-reactive (auto-reactive).FalseReceptor editing is when a B cell edits its heavy chain gene to become self-tolerantFalseReceptor editing involves DNA double-strand cutting and ligating on chromosomes 2 and/or 22.TrueAnergy belongs to the peripheral toleranceTrueCentral tolerance means that B cells inside the bone marrow are selected against if they don't lose self-reactivity.TrueBAFF is secreted by follicular dendritic cells that reside in the bone marrowFalseBAFF is received by immature B cells that come in close contact with follicular dendritic cells, and the B cells mature as a result of the BAFF signal.TrueThe light chain determines to which of the 5 classes of immunoglobulins an antibody belongs.FalseThe hinge region of an antibody (or B-cell receptor) determines the flexibility of the armsTrueThe antigen-binding site of each antibody (or B-cell receptor) arm is made of the N-termini of both the heavy and the light chain.TrueIgG is the most common antibody in blood and lymph. However, IgM is always made first, and IgD shows up second.TrueOnly after a mature, naïve B cell finds antigen, it can be stimulated by helper T cells to become an antibody-secreting plasma cellTrueImmunoglobulin domains protect antibodies from destruction by bacterial proteases as well as salt concentration and pH changes.TrueIn both light and heavy chains, the immunoglobulin domain closest to the C terminus contains three hypervariable regionsFalseConsidering the heavy chain, when is the primary RNA transcript made; before or after the VDJ segments are joined?AfterConsidering the light chain, how is the variable region fused to the constant region?By RNA splicingConsidering the heavy chain, how is isotype switching from IgM to either IgA, IgG or IgE accomplished?By an additional DNA recombination event that brings the new constant region closer to the promoter.The difference in making IgM and IgD comes down to the alternative splicing of the same primary RNA transcript.TrueAfter encountering antigen in the T-cell area, some B cells go the quick route to become plasma cells that secrete pentameric IgM without changing the antigen specificityTrueAfter encountering antigen in the T-cell area, many B cells switch to a different type of immunoglobulin (IgA, IgG or IgE). They also undergo somatic hypermutation, followed by affinity maturation. These processes happen in the B-cell area.TrueDuring somatic hypermutation, B cells divide. With every cell division, the variable regions of the heavy and light chain genes get a mutation introduced. This speeds up evolution to gain better antigen-binding sites.TrueWhen a B cell finds antigen, the B-cell receptor gets cross-linked by the antigen. This signal is not enough to activate the B cell. A second signal is necessary, which is mediated by the B-cell co-receptor binding to C3d on the pathogen surfaceTrueWhen a B cell decided to become a plasma cell that will secrete pentameric IgM, will it also give rise to memory B-cells?NoWhat surface immunoglobulin classes do memory B cells carry?The ones to which the isotype switched, when they were centroblasts.hymus-independent-1 antigens provide the third signal needed to activate a B-1 B cell, which leads to the development into IgM-secreting plasma cellsTrueThymus-independent-2 antigens activate B cells so strongly that a third signal is not needed.TrueTwo well-known thymus-independent-1-antigens are LPS and bacterial DNA, both of which send their signals through Toll-like receptors.TrueA cognate interaction is when a B cell makes close contact to a helper T cell that is specific for the same antigen that the B cell recognizes. They then migrate together to various places in the lymph node.TrueCentroblasts undergo affinity maturation, while centrocytes do the isotype switching and somatic hypermutation.FalseDimeric IgA is made and functions in mucosal tissues, while monomeric IgA is found in the blood. IgA is made as a result of isotype switchingTrueIgE mediates allergies and is also responsible for fighting parasitic infections. It is one of the antibodies that can result from isotype switchingTrueNatural killer cells can recognize IgG bound to human cells and kill these cells by a process called antibody-dependent cell-mediated cytotoxicity.TrueErythrocytes help cleaning up immune complexes by bringing them to macrophages in the liver and spleen.TrueMast cells collect IgE molecules of all antigen specificities. They bind them to their surface, so that the variable regions point outward. When an antigen crosslinks two of these receptors, histamine and other active substances will be released.True
