Immunology Quiz -the T Cell Receptor (Tcr)

T cells are generally found in the thymus. The thymus is a specialized organ of the immune system where T cells undergo maturation and development. T cell receptor (TCR) rearrangement, which is essential for the generation of a diverse T cell repertoire, occurs in the thymus. Therefore, the thymus is the main location for T cell development and TCR rearrangement.

The process used to increase antigen binding affinity is called hypermutation, which occurs in B cells but not T cells. Hypermutation is a process in which the DNA of B cells undergoes high rates of mutation, leading to the generation of a diverse repertoire of antibodies with different affinities for antigens. This process allows B cells to produce antibodies that have a higher affinity for specific antigens, improving the immune response. T cells, on the other hand, do not undergo hypermutation and rely on other mechanisms to recognize antigens.

Allelic exclusion is the correct answer because it refers to the process where a B cell successfully rearranges one heavy chain locus on one chromosome, and as a result, inhibits the rearrangement of the other heavy chain on the other chromosome. This ensures that each B cell expresses only one type of heavy chain, allowing for the production of diverse antibodies.

Analyses of protein and nucleic acid sequence data for TCRs with different specificities have revealed the existence of three hypervariable (hv) regions within the variable region.

The correct answer is Beta ("); Alpha (!). In the arrangement of TCR genes and BCR genes, the beta chain is analogous to the heavy (H) chain and the alpha chain is analogous to the light (L) chain.

The correct answer is Beta ("); Delta (#). This is because D-segments are present in both the Beta (") and Delta (#) chains of the TCR genetic chains, similar to immunoglobulin heavy chains. The other options do not include both Beta (") and Delta (#) chains.

Superantigens such as staphylococcal enterotoxins bind to certain TCR Beta chains and to MHC class II molecules. This binding does not involve the peptide groove. When T cells are activated by this binding, they can release extremely high levels of cytokines, leading to toxic shock syndrome (TSS) when these cytokines appear in the blood.

The T-cell receptor (TCR) is a type of protein that is found on the surface of T-cells, which are a type of immune cell. The TCR is comparable to an immunoglobulin fragment, specifically the Fab region. The Fab region of an immunoglobulin is responsible for binding to antigens, and in the case of the TCR, it binds to specific antigens on the surface of other cells. The TCR is membrane-bound, meaning it is attached to the cell membrane of T-cells, and it has a short cytoplasmic tail. This allows the TCR to interact with antigens and trigger an immune response.

If both RAG-1 and RAG-2 mutations occur, T and B cells will be absent but NK cells will be present. RAG-1 and RAG-2 are essential genes involved in the rearrangement of antigen receptor genes during the development of T and B cells. Without functional RAG-1 and RAG-2 proteins, T and B cells cannot undergo the necessary gene rearrangements and therefore cannot develop. However, NK cells do not require RAG-1 and RAG-2 for their development and will still be present.

The TCR genetic chains that contain V and J segments, similar to genes for immunoglobulin kappa and lambda light chains, are the Gamma ($); Alpha (!) chains.

Deficiencies in RAG-1 or RAG-2 lead to autosomal-recessive severe combined immunodeficiency disease (SCID). RAG-1 and RAG-2 are enzymes that are essential for the process of V(D)J recombination, which is necessary for the development of functional T and B cells. Without proper V(D)J recombination, the immune system is unable to generate a diverse repertoire of T and B cell receptors, resulting in SCID. Therefore, deficiencies in either RAG-1 or RAG-2 can lead to this immunodeficiency disease.

Lambda delta T cells do not recognize peptide antigens by MHC and are hypothesized to be a primary line of immune defense.

Allelic exclusion is a process where only one allele is expressed while the other allele(s) are silenced. In the context of the given options, the correct answer is "B cells and TCR beta chains, but not in alpha chains". This means that in B cells and TCR beta chains, only one allele is expressed, while the other allele(s) are silenced. However, in TCR alpha chains, both alleles are likely to be expressed, and in B cells, both alleles are also likely to be expressed.

The correct answer is B & C. The human T-cell receptors, specifically the alpha and beta chains, are located in chromosome 7. The gamma chain is also located in chromosome 7. Therefore, options B and C are the correct choices as they include the alpha and beta chains, and the gamma chain respectively, all of which are located in chromosome 7.

The correct answer is Chromosome 14 within the alpha (!)-locus. This means that the delta-chain locus, which is a part of the human T-cell receptors, is located on Chromosome 14 within the alpha (!)-locus.