Anti Body Diversity In Immunology MCQ Quiz Question & Answers

The correct answer is Lambda (l) and kappa (k). These are the two types of light chains found in antibodies. Light chains are a component of the antibody structure and are responsible for binding to antigens. Lambda and kappa refer to the different types of light chains that can be present in antibodies. They are named based on their distinct amino acid sequences and have slightly different functions within the immune system.

Diversity (D) is the only option that is exclusively found in heavy chains and not in light chains. Heavy chains and light chains are two types of polypeptide chains that make up antibodies. The heavy chains are larger and contain additional regions, such as the Diversity (D) region, which contribute to the diversity of antibodies. Light chains, on the other hand, do not have a Diversity (D) region. Therefore, Diversity (D) is the correct answer as it is specific to heavy chains only.

IgD and IgM are frequently found on the surface of B cells co-expressed with each other. These two classes are co-expressed not by class switching but by alternative processing of a primary RNA transcript. Both molecules expressed on the single mature B cell have the same binding specificity for antigen.

In somatic recombination, the heavy chain rearranges first. The Fab region of the antibody molecule is generated via somatic recombination as it binds to the antigen and contains both a constant region and a variable region.

Antibody diversity is generated through various mechanisms, including germline diversity, combinatorial diversity, junctional diversity, and somatic hypermutation. Germline diversity refers to the presence of multiple copies of V, D, and J gene segments, allowing for a wide range of possible combinations. Combinatorial diversity occurs when VJ and VDJ gene segments recombine in different combinations, further increasing the diversity. Junctional diversity is achieved through different sequences at the joint, leading to even more antibody diversity. Somatic hypermutation, which occurs after antigenic stimulation, introduces random mutations in the antibody genes, resulting in additional diversity. Therefore, the statement that a single combination of light and heavy chains is true regarding the mechanisms of generating antibody diversity.

During the final step of synthesis for heavy and light immunoglobulin chains, the leader (L) peptide is cleaved. The leader peptide is a short sequence of amino acids that helps in the targeting and transport of the newly synthesized protein to its correct location within the cell. Once the protein reaches its destination, the leader peptide is cleaved off, allowing the mature immunoglobulin chain to function properly.

If alternative processing uses the first polyadenylation site, the type of heavy chain mRNA derived is (mu).

If alternative processing uses the second polyadenylation site, the heavy chain mRNA derived would be of the delta type.

The production of secreted antibodies (pAs site) involves a shorter chain of amino acids with a stretch of charged (versus non charged) amino acids at the COOH terminus, in comparison to membrane bound antibody production (pAm site).

According to allelic exclusion, a particular B cell can only express one type of Ig. In heterozygous individuals with two alternative forms of the constant region gene for IgG1 (IgG1m(1) and IgG1m(2)), the B cell will only express one of these types, not both.

Class switching (isotype switching) involves rearrangement of the V(H) exon to associate with a different C(H) exon at different times in the course of an immune response. The Fc region of the antibody molecule is affected (changed) via class switching and, unlike somatic recombination, this process is antigen dependent.

Immunoglobulin chains, comprising heavy and light polypeptide chains, possess variable (V) and constant (C) regions crucial for immune function. These chains are encoded by sets of gene segments. During B cell development, these gene segments undergo rearrangement to assemble a functional gene, encoding either a heavy or a light chain. This rearrangement process ensures diversity in antibody recognition, crucial for an effective immune response. Unlike T cells, which also play critical roles in immune function, B cells undergo this rearrangement process within their genome to generate the diverse repertoire of immunoglobulin molecules required to recognize and respond to a wide range of pathogens.

During the development of B cells, the Ig gene segments undergo somatic recombination, where they are rearranged and brought next to each other to form a functional gene. The complex of enzymes involved in this process is called V(D)J-lyase. This enzyme complex, consisting of RAG-1 and RAG-2 (Recombination-Activating Genes), is responsible for cleaving and rejoining the gene segments to create a contiguous gene. Therefore, the correct answer is V(D)J-lyase.