Ch4 - Antigen recognition in the adaptive immune system Flashcards
IN the adaptive immune system, the molecules responsible for specific regions of antigens are ___?
antibodies and T cell antigen receptors
Antibodies are also called ___?
Immunoglobins
Antibodies may be produced as membrane receptor of __?
B lymphocytes
- and as proteins secreted by antigen stimulated B cells that have differentiated into antibody secreting plasm cells
What are the effector molecules of humoral immunity?
secreted antibodies
What are secreted antibodies capable of?
- neutralising microbes and microbial toxins
- eliminating them by activating various effector mechanisms
T cell receptors (TCRS) are _____ receptors?
- membrane
- they aren’t secreted
Describe the structure of an antibody?
- core structure has 2 identical heavy chains and 2 identical light chains
- form a disulphide- linked complex
- each chain has a variable (v) region and a constant (c) region
WHat does the variable region of an antibody do?
recognises the antigen
WHat does the constant region of the antibody do?
provides structural stability
in heavy chains performs the effector functions of antibodies
Q - What are the functionally distinct domains (regions) of antibody and TCR molecules? What features of the amino acid sequences in these regions are important for their functions?
Antibody and T cell receptor (TCR) proteins contain variable domains that are involved in antigen recognition and constant domains that, in the case of antibodies, mediate effector functions. Variable domains contain hypervariable regions (sequences that differ among different antibodies or TCRs) that form the binding sites for antigens.
Q- What are the differences in the types of antigens recognized by antibodies and TCRs
Antibodies can recognize many types of molecules, including small chemicals, proteins, carbohydrates, lipids, and nucleic acids. In proteins, antibodies can recognize conformational or linear epitopes. TCRs can recognize only linear peptides that are proteolytically generated from proteins and bound to the clefts of MHC molecules.
Q- What mechanisms contribute to the diversity of antibody and TCR molecules? Which of these mechanisms contributes the most to
Diversity of antibodies and TCRs is generated by V-D-J recombination, which is the joining of DNA segments in developing lymphocytes that are spatially separated in the inherited DNA of antibody and TCR gene loci. Variations in nucleotide sequences introduced by the use of different V, D, and J segment combinations (combinatorial diversity), and during V-D-J joining (junctional diversity) contribute to diversity, with junctional alterations making the largest contribution
Q- What are some of the checkpoints during lymphocyte maturation that ensure survival of the useful
Checkpoints in lymphocyte development are molecular events that must be successfully completed to permit survival and further maturation of the cells. The first checkpoint in B and T cell maturation involves the selection of pre-B and pre-T cells that have productively rearranged the μ heavy-chain gene in the case of B lineage cells and the TCR β chain gene in the case of developing T cells. The second checkpoint is after production of complete antigen receptors and ensures that only cells with the proper V-D-J recombination can mature. Positive selection is a process in which T cells that can recognize self MHC molecules weakly are allowed to survive and express the type of coreceptor that matches the type of MHC molecule recognized.
Q- What is the phenomenon of negative selection, and what is its importance?
Negative selection results in the deletion or editing of strongly self-reactive lymphocytes. This process eliminates many self antigen–reactive lymphocytes, in the thymus for T cells and in the bone marrow for B cells.
