Question

Which of the following IgH chains is NOT produced as a result of CSR?

A. d
B. a1
C. ?
D. ?2
E. None of the above is produced as a result of CSR.

Answer 1

IgD is the IgH chain not produced as a result of CSR; it is expressed on naive B cells' surface. CSR enables B cells to produce IgG, IgA, or IgE instead of IgM but does not involve IgD.

Step-by-step explanation:

Among the options provided, IgD is the immunoglobulin heavy (IgH) chain that is NOT produced as a result of class-switch recombination (CSR). This class of antibody is expressed on the surface of naïve B cells rather than secreted. CSR is a mechanism in B cells that changes the constant region of the antibody heavy chain, allowing the same antibody to be produced with different effector functions.

This process allows for the production of IgG, IgA, or IgE from initially secreted IgM, but not IgD, which remains expressed on the B cell surface for antigen recognition and B cell maturation.

Answer 2

IgD is the correct option as it is not produced as a result of class switch recombination (CSR) but is expressed on the surface of naïve B cells.

Step-by-step explanation:

In immunology, the question refers to the process known as class switch recombination (CSR), which is how different antibody classes are produced.

CSR is a mechanism that allows an immunoglobulin heavy chain (IgH) to change from one isotype to another (e.g., from IgM to IgG, IgA, or IgE) in response to antigenic stimulation, thereby changing the type of antibody secreted by B cells. Considering the options provided and the context of the question, the answer is E. IgD.

IgD is a class of antibody that, similar to IgM, is expressed on the surface of naïve B cells. It is not produced as a result of CSR; instead, naive B cells express it alongside IgM. This process of CSR is crucial for the adaptive immune system's ability to generate a more effective immune response to pathogens.