Recognition of antigens by the adaptive immune system Flashcards
What is an antigen, and how does the adaptive immune system recognize it?
An antigen is any molecule or molecular structure recognized by the immune system. The adaptive immune system recognizes antigens through specific receptors, such as antibodies on B cells and TCRs on T cells.
What cells produce antibodies?
B cells get activated to become plasma cells.
Plasma cells secrete antibodies
Describe the structure and function of an antibody and the role of hypervariable regions
Structure: Antibodies consist of two identical heavy chains and two identical light chains, connected by disulfide bonds. Each chain has a variable region responsible for antigen binding and a constant region that mediates effector functions.
The hypervariable regions, also known as complementarity-determining regions (CDRs), are located at the antigen-binding sites and determine the antibody’s specificity by interacting with specific epitopes on antigens.
Antibodies neutralize pathogens by blocking their binding to host cells, opsonize them for phagocytosis, and activate the complement system to enhance pathogen clearance.
What are the structural components of the T cell receptor (TCR)?
TCRs are composed of two chains, usually alpha and beta, each with variable and constant regions. The variable region contains hypervariable regions that interact with peptide-MHC complexes, providing specificity to the TCR.
How do B cells respond to antigen binding, and what are the outcomes of this activation?
Upon binding an antigen, B cells are activated, leading to proliferation and differentiation into plasma cells and memory B cells. Plasma cells produce antibodies specific to the antigen, while memory B cells provide long-term immunity.
Generation of Antibody and TCR Diversity
Mechanisms:
Diversity in antibodies and TCRs is generated by somatic recombination of V, D, and J gene segments, junctional diversity, and somatic hypermutation (for antibodies).
Importance:
This diversity enables the immune system to recognize and respond to an extensive variety of antigens, essential for adaptive immunity.
