Immunology: Antibody Production and Structure PDF

## The Genes That Determine the Constant Regions - Downstream from the VDJ regions, there are regions with one gene for the non-coding of a heavy chain (beta, gamma, etc.). - When a VDJ region is spliced, a primary transcript of DNA is formed, including an intermediate region and a constant region....

## The Genes That Determine the Constant Regions - Downstream from the VDJ regions, there are regions with one gene for the non-coding of a heavy chain (beta, gamma, etc.). - When a VDJ region is spliced, a primary transcript of DNA is formed, including an intermediate region and a constant region. - During splicing, the intermediate region is cleaved, and the constant and variable regions are connected. - In heavy chains, there are introns in the C region. - These introns are also cleaved during splicing. - The heavy chain has 5 genes that each code for a different constant region. - The first regions to be encoded downstream of J are mu and delta. - The newly formed VDJ region initially joins C mu or C delta through alternative splicing. - B cells exiting the bone marrow can produce two types of antibodies: IgM or IgD. - When the cell first encounters an antigen, the heavy chain needs to transition from membrane-bound to secreted. ## Switch Region: - The VDJ region remains the same in memory cells. As long as the cell lives, this sequence remains unchanged. The heavy chain undergoes a switch in type, which is possible with each of the three downstream genes to delta during a memory response. - Downstream and upstream to each gene in the constant region of the heavy chain, there is a switch region. They can hybridize to create a loop during secondary recombination in response to antigen encounter. - The switch process occurs between two heavy chain genes and the connection between the two switch regions creates a stem and loop structure where the enzyme cleaves and creates a shortened chain: VDJ linked to a constant region encoding alpha, gamma, or epsilon, generating IgA. - There is a hierarchy in antibody production: Initially, IgM/IgD is produced and then, after a secondary response, IgA, IgE and IgG can be produced. - A cell that has undergone secondary IgG-IgM rearrangement cannot form a new rearrangement. ## Membrane Constant - Downstream of C, there are two additional sequences: a sequence encoding hydrophobic amino acids (membrane constant) which sits on the membrane receptor and a sequence of hydrophillic amino acids (secreted terminus). - When the antibody is secreted, it must carry this sequence and not the membrane sequence. - During the initial intervention of the heavy chain, the membrane terminus is embedded in the lipid membrane of the receptor. - This sequence changes from hydrophobic to hydrophilic by switching the receptor. - It has a cysteine residue which acts to create a pentamer.