Question

1. The pre-B-cell receptor provides an important signal that induces transition of pro-B cells to pre-B cells. An important characteristic of this receptor is that:
A. It signals without binding to an extracellular ligand.
B. It is composed of immunoglobulin heavy chains and the VJ region of a rearranged gamma light chain.
C. It is expressed at very high levels on the surface of the pro-B cell.
D. It signals without requiring association with B-cell receptor signaling subunits, Igalpha and Igbeta

2. The vaccine to Haemophilus influenzae type b is called a conjugate vaccine. It is composed of the tetanus toxoid protein conjugated to the capsular polysaccharide of the H. influenzae type b bacteria. When used to vaccinate infants, the antibody response generated by this vaccine would include:
A. Antibodies to the bacterial polysaccharide and the tetanus toxoid
B. Antibodies to the tetanus toxoid only
C. Antibodies to the bacterial polysaccharide only
D. Antibodies that only bind to the protein-polysaccharide conjugate in the vaccine
E. Antibodies that recognize the polysaccharide capsule
when shed by the bacteria
E. It signals without requiring the B-cell receptor signaling kinase, BTK.

3. CXCR5 is the receptor for the chemokine CXCL13, secreted by follicular stromal cells and follicular dendritic cells in the B cell zones (i.e., lymphoid follicles) of secondary lymphoid organs. A conditional knockout mouse in which CXCR5 was specifically deleted only in T cells would have:
A. No defects in any type of antibody response
B. Defects in the initial activation of all B cells
C. A lack of discrete B cell and T cell zones in the
lymphoid organ
D. A defect in T cell-dependent antibody responses
E. An increased number and size of germinal centers

Answer 1

Ans 1)

b) It is composed of immunoglobulin heavy chain and VJ region of rearranged gamma light chain.

This means when the conversion process takes place changing the pro B-cells to pre B-cells, the receptor provides an important signal and it has that particular configuration which leads to the process of conversion. It is a step wise process of rearrangement where the V, D and J segments of the heavy and light chains are neatly rearranged.

Ans 2)

c) Antibodies to the bacterial polysaccharide only

The polysaccharide that is present in the bacteria imparts it protection and does not allow the organism to be destroyed. When this vaccine is given to the patient, it acts against the polysaccharide in the infants and weakens it to prevent Hemophilius Influenzae.