Micro Bio Unit 3 Flashcards
Chapter 18
cellular immunity
antibodies produced by B cells
humoral immunity
antibodies produced by B cells
- Distinguish between antigen, immunogen, epitope and hapten
Antigens, also called immunogens, are molecules that activate adaptive immunity. A single antigen possesses smaller epitopes, each capable of inducing a specific adaptive immune response.
Such molecules, called haptens, are essentially free epitopes that are not part of the complex three-dimensional structure of a larger antigen. For a hapten to become antigenic, it must first attach to a larger carrier molecule (usually a protein) to produce a conjugate antigen.
Diagram a generic IgG, label the Fab and Fc
Antibodis contain two main regions
Fc – region that can activate complement and binds to phagocytic cells
Fab – binds to antigens.
Each B cell clone has a unique Fab
Neutralization
involves the binding of specific antibodies to antigens found on bacteria, viruses, and toxins, preventing them from attaching to target cells
agglutination
Antibodies, especially IgM antibodies, agglutinate bacteria by binding to epitopes on two or more bacteria simultaneously. When multiple pathogens and antibodies are present, aggregates form when the binding sites of antibodies bind with separate pathogens.
opsonization
Opsonization- to “tag” or “put a handle on”
Opsonized pathogens are tagged for destruction by macrophages, dendritic cells, and neutrophils.
These phagocytic cells use Fc receptors to bind to IgG-opsonized pathogens and initiate the first step of attachment before phagocytosis.
- Explain why adaptive responses to pathogens occur more quickly and robustly at the second exposure.
Some B cells will become “Memory B cells”
Memory B cells can secrete antibody much more quickly the next time they “see antigen”. This secondary response could be as short as a few days
- List the cells that are able to present antigen AND activate T cells
dendritic cells macrophages and B cells
- Differentiate between the cells that produce MHCI and MHCII
MHC I - Present peptides (fragments of proteins) from within the cell. This can allow immune cells to surveil for cancer or intracellular infections. ALL NUCLEATED CELLS DO THIS
MHC II – presents peptide taken up by phagocytosis and digested. This allows immune cells to surveil for extracellular pathogens. ONLY PROFESSIONAL APCs DO THIS.
- Understand the role of CD4 helper T cells
Helper T cells are activated when they are presented with a peptide the recognize by an APC via MHC II, they provide help signals through cytokines to other cells in the immune system.
TH1 cells
TH1 cells also stimulate macrophages and neutrophils to become more effective in their killing of intracellular bacteria. They can also stimulate NK cells to become more effective at killing target cells.
TH2 cells
Stimulate B cell activation and differentiation into plasma cells and memory B cells
Direct antibody class switching in B cells
- Understand the role of Regulatory T cells
Therefore, a second line of defense called peripheral tolerance is needed to protect against autoimmune disease. Peripheral tolerance involves mechanisms of anergy and inhibition of self-reactive T cells by regulatory T cells
- Understand which type of T cell recognizes and eliminates intracellular pathogens
Cytotoxic T cells are activated when they are presented a peptide they recognize by and APC via MHC I. Then, they circulate through the body killing cells that are infected with the pathogen they are specific for. Killing is mediated by perforin and granzymes that induce apoptosis (programmed cell death).
CD8
