Question 1

For each of the descriptions in questions ,select the B cell signaling molecule (A-I)that most closely matches it.
-A protein that is the cell surface receptor for Epstein-Barr virus

Accepted Answer

Complement receptor 2 (CR2;gp140)is the cell surface receptor for Epstein-Barr virus (EBV)and mediates EBV entry into the cell.CR2 also serves as a coreceptor with the B cell receptor,mediating complement-dependent enhancement of B cell activation.

Question 2

For each of descriptions in questions ,select the letter of the Ig isotype (A-E)that most closely matches it.Answers may be used more than once.
-An allergic reaction

Accepted Answer

IgE antibodies play an essential role in immediate-type hypersensitivity reactions (e.g. ,allergies),asthma,and helminthic infections.Mast cells express plasma membrane FcF1F1F1S1F1F1F10 receptors,which bind IgE antibodies specific for allergens that were produced after a prior exposure to allergens.On re-exposure to an allergen that binds to some of the IgE antibodies bound to the mast cell,the mast cells are activated and rapidly release histamine and other vasoactive and inflammatory molecules.

Question 3

A child is infected with a virus,mounts antibody responses to a viral protein,and recovers.One year later,the child is exposed to the same type of virus,and mounts a memory response specific to the same viral protein.Which one of the following statements comparing the (primary)antibody response to the viral protein and the memory response a year later is true?

Accepted Answer

B cell responses to protein antigens require Tfh cells.In a primary immune response,short-lived plasma cells are generated which secrete low affinity IgM antibodies against the protein antigens,but as the response develops,Tfh cells induce isotype switching,production of IgG with high affinity for antigen,memory B cells,and long lived plasma cells.In the memory response,memory B cells are rapidly activated to become plasma cells that produce high levels of high affinity IgG.

Question 4

For each of descriptions in questions ,select the letter of the Ig isotype (A-E)that most closely matches it.Answers may be used more than once.
-T cell-independent antigens

Accepted Answer

All B cell initially make IgM and IgD,and not other isotypes.Most isotype switching from IgM to other isotypes depends on T cells help.Therefore in responses to T cell-independent antigens,which are non-protein antigens,the main isotype is IgM.
Multiple Choice

Question 5

For each of the descriptions in questions ,select the B cell signaling molecule (A-I)that most closely matches it.
-A protein tyrosine kinase homologous to Zap-70,which phosphorylates several adaptor proteins and enzymes

Accepted Answer

The tyrosine kinase Syk binds through its SH2 domains to the phosphotyrosine residues on the cytoplasmic tails of IgF1F1F1S1F1F1F10 and IgF1F1F1S1F1F1F10.On activation,Syk,in turn,activates numerous downstream signaling molecules,including B cell linker protein (BLNK).BLNK serves as a scaffolding protein for the activation of different pathways,including the Ras-MAP kinase pathway,the phospholipase C pathway with calcium release,and Btk activation.Ultimately,many of the same transcription factors that are important in T cell activation also mediate B cell activation,including NFAT,AP-1,and NF-F1F1F1S1F1F1F10B.

Question 6

For each of descriptions in questions ,select the letter of the Ig isotype (A-E)that most closely matches it.Answers may be used more than once.
-Binds to receptors in the gastrointestinal tract of infants for absorption into the serum

Accepted Answer

Neonatal immunity is mediated in part by antibodies in breast milk,which are absorbed in the gastrointestinal tract by specific Fc receptors.These receptors are specific for the IgG isotype and are called FcF1F1F1S1F1F1F10RN (N for "neonatal").Absorption of antibodies from the mother's breast milk is a primary mode of immunity for the first 6 months of life,before the infant has produced significant amounts of antibody on its own.

Question 7

For each of descriptions in questions ,select the letter of the Ig isotype (A-E)that most closely matches it.Answers may be used more than once.
-Unclear functional role

Accepted Answer

IgD is expressed mainly as a membrane but not secreted Ig by naive B cells,and its function is unclear.

Question 8

For each of descriptions in questions ,select the letter of the Ig isotype (A-E)that most closely matches it.Answers may be used more than once.
-Phagocytosis

Accepted Answer

Phagocytosis is primarily mediated by neutrophils and macrophages during an immune response to an infection.Both cell types express FcF1F1F1S1F1F1F10 receptors,which bind to the constant regions of IgG antibodies that have bound to microbes.The FcF1F1F1S1F1F1F10 receptors then activate the cells to phagocytose the antigen-coated microbes.

Question 9

For each of the descriptions in questions ,select the B cell signaling molecule (A-I)that most closely matches it.
-An Src family kinase that phosphorylates ITAMs in the cytoplasmic tails of B cell receptor complex proteins

Accepted Answer

On antigen-mediated cross-linking of the B cell receptor (BCR),the ITAMs of IgF1F1F1S1F1F1F10 and IgF1F1F1S1F1F1F10 are phosphorylated by Src family kinases,including Fyn,Lyn,and Blk.This initiates the signaling cascade for B cell activation.

Question 10

Which one of the following statements about humoral immune responses is true?

Accepted Answer

Humoral responses require antigen-dependent activation of B cells through binding of the antigen to membrane Ig on naive B cells or on memory B cells,for primary or secondary responses,respectively.In most cases,nonprotein antigens do not stimulate isotype switching or affinity maturation because these changes require T cell help,and only protein antigens can stimulate T cells.For both nonprotein and protein antigens,antibody-secreting cells that are generated may live for months,often in the bone marrow.

Question 11

For each of the descriptions in questions ,select the B cell signaling molecule (A-I)that most closely matches it.
-A protein that covalently binds to microbes and serves as a ligand for a coreceptor that enhances B cell responses to antigen

Accepted Answer

C3d is a complement protein fragment that binds covalently to microbial surfaces.C3d serves as the link between the BCR,which binds directly to the microbe,and the CR2 coreceptor.This cross-linking between the BCR and CR2 serves to amplify the B cell response 1000-fold when compared with immune responses in which CR2 is not recruited.CR2 forms a complex with two other proteins,CD19 and CD81,on the B cell surface.When CD19 is brought into proximity with BCR-associated kinases,the cytoplasmic tail of CD19 is rapidly phosphorylated.CD19 then activates several signaling pathways,including PI3-kinase.

Quiz 14: B-Lymphocyte-Activation

For each of the descriptions in questions ,select the B cell signaling molecule (A-I) that most closely matches it. -A protein that is the cell surface receptor for Epstein-Barr virus

For each of descriptions in questions ,select the letter of the Ig isotype (A-E) that most closely matches it.Answers may be used more than once. -An allergic reaction

For each of descriptions in questions ,select the letter of the Ig isotype (A-E) that most closely matches it.Answers may be used more than once. -T cell-independent antigens

For each of the descriptions in questions ,select the B cell signaling molecule (A-I) that most closely matches it. -A protein tyrosine kinase homologous to Zap-70,which phosphorylates several adaptor proteins and enzymes

For each of descriptions in questions ,select the letter of the Ig isotype (A-E) that most closely matches it.Answers may be used more than once. -Binds to receptors in the gastrointestinal tract of infants for absorption into the serum

For each of descriptions in questions ,select the letter of the Ig isotype (A-E) that most closely matches it.Answers may be used more than once. -Unclear functional role

For each of descriptions in questions ,select the letter of the Ig isotype (A-E) that most closely matches it.Answers may be used more than once. -Phagocytosis

For each of the descriptions in questions ,select the B cell signaling molecule (A-I) that most closely matches it. -An Src family kinase that phosphorylates ITAMs in the cytoplasmic tails of B cell receptor complex proteins

Which one of the following statements about humoral immune responses is true?

For each of the descriptions in questions ,select the B cell signaling molecule (A-I) that most closely matches it. -A protein that covalently binds to microbes and serves as a ligand for a coreceptor that enhances B cell responses to antigen