16 Questions
How can B-cells be activated?
Through direct recognition of antigen via B-cell receptors
What do B-cells become after activation and clonal expansion?
Antibody producing plasma cells
Which antibody is most abundant in the blood and can cross the placenta?
IgG
What is the function of IgA antibodies?
Protect mucus membranes against adhesion of virus and bacteria
Which antibody is involved in allergic reactions?
IgE
What is the primary role of IgM antibodies?
First antibody to be secreted by plasma cells following activation
What are serum IgG antibody titers like during a secondary immune response?
Much higher and much faster than the primary response
Which part of the antibody structure is responsible for antigen binding?
Antigen binding sites
What feature is a hallmark of adaptive immunity?
Specificity for particular foreign molecules
What do B cells differentiate into when activated?
Plasma cells
What type of antigens do cytotoxic T cells target?
Virus-infected cells
What is the role of helper T cells in cell-mediated immunity?
Activate other immune cells
How are exogenous antigens processed and presented?
Bound to MHC-II molecules by APCs
What type of antigen is presented on MHC-I molecules?
Endogenous antigens
Which type of cell is directly responsible for killing virus-infected cells?
Cytotoxic T cells
What provides long-term immunity in both antibody-mediated and cell-mediated immunity?
Memory cells
Study Notes
Adaptive (Specific) Immunity
- Adaptive immunity involves specificity for particular foreign molecules (antigens) and memory for most previously encountered antigens.
- Memory response is faster and greater than the initial response.
Antibody Mediated Immunity
- B cells are activated by antigens and differentiate into plasma cells that secrete antibodies.
- Antibodies bind to antigens and neutralize them or mark them for destruction by other cells.
- Memory B cells are formed, providing long-term immunity.
Cell-Mediated Immunity
- Cytotoxic T cells kill virus-infected cells and some cancer cells.
- Helper T cells activate other immune cells, including B cells and cytotoxic T cells.
- Memory T cells are formed, providing long-term immunity.
Processing and Presentation of Antigens
- Exogenous antigens are taken up by APCs, broken down into peptides, and bound to MHC-II molecules.
- MHC-II/peptide complex is recognized by Helper T cells, which then become activated.
- Endogenous antigens are generated from within the cell, broken down into peptides, and bound to MHC-I molecules.
- MHC-I/peptide complex is recognized by cytotoxic T cells.
Antibody Structure and Functions
- Antibodies (immunoglobulins) have a single-unit structure with antigen binding sites, light and heavy chains, and variable and constant domains.
- Antibody classes include IgG, IgA, IgM, IgE, and IgD, each with distinct functions and characteristics.
Antibody Classes and Functions
- IgG: neutralizes bacterial and viral toxins, enhances phagocytosis, activates complement, and crosses the placenta for fetal immunity.
- IgA: protects mucus membranes against adhesion of virus and bacteria.
- IgM: activates complement, causes agglutination and lysis of bacteria, and is the first antibody to be secreted by plasma cells.
- IgE: involved in allergic reactions and defence against parasites.
- IgD: found on the surface of B-cells as an antigen receptor.
Immunological Memory and Vaccination
- Immunological memory involves thousands of memory cells that exist after initial encounter with an antigen.
- Memory cells can proliferate and differentiate within hours upon subsequent exposure to the same antigen.
- Serum IgG antibody titers are much higher and faster on the second response.
Learn about the adaptive immune response, its key features, and antibody-mediated immunity in this chapter of immunology.
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