The immunoglobulin heavy-chain that is rearranged first and is displayed on the surface of early stages of B-cell development is associated with:
a surrogate light chain.
Immunoglobulin Heavy Chain Rearrangement in B Cell Development
B cell development is a complex process involving several stages, where B cells acquire the ability to produce antibodies. A crucial step in this development is the rearrangement of immunoglobulin (antibody) genes. These genes exist in segments (V, D, J, C) in the germline DNA. During development, these segments are cut and joined together in a process called V(D)J recombination.
The immunoglobulin heavy chain genes are rearranged first. This rearrangement process happens in pro-B cells. If a functional heavy chain gene is successfully rearranged, the cell moves to the pre-B cell stage.
Pre-B Cell Receptor and Surrogate Light Chain
In the pre-B cell stage, the successfully rearranged immunoglobulin heavy chain is expressed. To signal that a functional heavy chain has been produced and to allow the cell to survive and proliferate, this heavy chain is displayed on the surface of the pre-B cell. However, at this stage, the B cell has not yet rearranged its light chain genes. Therefore, the heavy chain needs a partner to be displayed on the surface and form a receptor complex.
This partner is a complex called the surrogate light chain. The surrogate light chain is made up of two proteins: VpreB and λ5. These proteins mimic a real immunoglobulin light chain and pair with the rearranged heavy chain to form the pre-B cell receptor (pre-BCR). The display of the pre-BCR on the cell surface is a critical checkpoint in B cell development, indicating successful heavy chain rearrangement and triggering signals for the cell to proliferate and then begin light chain rearrangement.
Thus, the immunoglobulin heavy chain that is rearranged first and displayed on the surface of early stages of B-cell development (specifically, pre-B cells) is associated with a surrogate light chain.
Considering Other Options
- Class-II associated invariant chain peptide (CLIP): CLIP is a peptide associated with MHC class II molecules. It prevents peptides from binding to the MHC class II molecule in the endoplasmic reticulum and Golgi before the MHC class II molecule reaches the late endosomes/lysosomes where it encounters external antigens. This is not involved in immunoglobulin heavy chain association during B cell development.
- β2-macroglobulin: This is a component of MHC class I molecules. MHC class I molecules are involved in presenting intracellular antigens to cytotoxic T cells. It is not associated with immunoglobulin heavy chains.
- Immunoglobulin-like cell adhesion molecule: These are proteins belonging to the immunoglobulin superfamily but are involved in cell-to-cell adhesion processes. While they share structural similarities with immunoglobulins, they do not pair with rearranged heavy chains to form the pre-BCR or BCR.
Therefore, the correct association for the first rearranged heavy chain displayed on early B cells is with a surrogate light chain, forming the pre-B cell receptor.
Important Questions from Immune System
Bacterial infections are generally divided into two broad classes: intracellular and extracellular bacterial infections. Given below are some of the properties which are applicable for bacterial infections.
A. Humoral immune response is the main protective response against extracellular bacteria.
B. Innate immunity is not effective against intracellular bacterial pathogens.
C. Bacterial endotoxins do not induce an innate immune response.
D. Intracellular bacterial infections generally induce a cell-mediated immune response resulting in secretion of cytokines which activate macrophages.
Which one of the following combination of statements is correct?
Dr. Ralph M. Steinman was awarded Nobel Prize for his discovery on:
Which one of the following systems forms a chemical mediator that is involved in the mechanism of pain during inflammation?
Suresh was bitten by a poisonous snake and was immediately treated with anti-venom human immunoglobulin and was saved. A year later he was bitten by the same type of snake second time. Predict his response to the venom from second bite from the following:
An antigen was injected into a mouse. Macrophages and antigen primed TH cells were isolated from this mouse to perform the following in vitro experiments:
A. Macrophages were treated with the antigen for an hour and then incubated with TH cells.
B. Macrophages were treated with paraformaldehyde first and then treated with the antigen for an hour. These macrophages were then incubated with T H cells.
C. Macrophages were treated with paraformaldehyde first then treated with the digested (proteolytically cleaved) antigen for an hour. These macrophages were then incubated with T H cells.
D. Macrophages were treated with the antigen for an hour and then treated with paraformaldehyde. These macrophages were then incubated with TH cells.
Which of the above experiments would lead to TH cells proliferation?
