CH. 24 Adaptive Immunity Flashcards
What is the humoral immune response? What cell type(s) are involved and what stimulates the response? What type of pathogen triggers the humoral immune response?
It is a composite of responses to different epitopes by thousands of B cells. They are most effective against EXTRACELLULAR PATHOGENS
B cells possess surface immunoglobulins that bind to their specific epitope (clonal selection) to activate the B cells, and usually require helper T cells to interact with each other (becomes T-dependent antigen)
What is an epitope?
They are smaller parts of antigens that is detected by the immune system for adaptive immune cells to bind to it
What is the basic structure of an antibody? What are the antigen‐binding sites?
It is shaped as a “Y”. The Fc region is the stem and on the very top branch-like of the structure are the heavy and light chains where the antigen-binding site is located. There is also a hinge region to hold the light and heavy chain
What are the types of immunoglobins? Describe the functions of each immunoglobins type
IgA (15%): dimer, found mainly on mucosal surfaces & in secretions. Prevents pathogen attachment to surfaces
IgG (75%): monomer; most abundant in blood & tissue fluids; opsonization, activate complement; neutralize viruses
IgD (0.2%): found on B cells & in blood, lymph
IgM (10%): pentamer; generally remains in blood vessels. FIRST Ab detected in immune response; effective in agglutination & complement activation
IgE (0.2%): found on surface of mast cells & basophils; causes release of histamine, other chemicals by these cells in presence of antigen. Can attract complement, phagocytic cells.
How do antibody isotypes differ from antibody idiotypes?
Isotypes differ in amino acid sequence of constant region of heavy chains
Idiotypes possess the same amino acid sequence of the constant region of heavy chains. but differ in regions of antigen-binding sites
Describe the primary and secondary antibody responses?
Primary Antibody Response:
-Following infection/vaccination, antibodies appear in serum after several days
-B cells that bind antigen differentiate into IgM->IgG and memory B cells
Secondary Antigen Response:
-Via a second exposure to pathogen or booster
dose due to memory B cells
–A much bigger, faster response with mostly IgG
What is the difference between plasma B cells and memory B cells?
Plasma B cells produces antibodies (active)
Memory B cells remembers antigen and react immediately when exposed (dormant until exposure)
What is clonal selection?
Rapid increase in the number of B cells that respond to a specific epitope
What is the cell‐mediated immune response? What cell types are involved? What is their role? What type of pathogen triggers the cell‐mediated immune response?
An immune response that involves T cells that differentiate into T helper cells and T cytotoxic cells
The response recognizes antigens that are presented to them on the surface of the cells infected with intracellular pathogens
T cytotoxic cells destroy the infected cells and T helper cells bind to MHC class II molecules to activate to release cytokines
What is the role of an antigen-presenting cell? What type of cells are these?
A cell that displays antigens on its surface for T cells for the stimulation of immune response
Some types are macrophages, dendritic cells, and B cells
What are MHC class I, II proteins? What is their function? How do MHC proteins correlate to T cells?
MHC Class I -> Cytotoxic T cell
-Target self-cells altered by infection with pathogen and target cancer cells
-Kill target cells via proteins and induction of apoptosis
MHC Class II -> T Helper cell
-Recognize antigens presented by antigen-presenting cells (dendritic cells & macrophages)
-Release of various cytokines (TH1 -> activate macrophages, complement, etc. & TH2 -> antibody production by B cells)
What are the different responses or effects that can result from antibody: antigen binding?
Agglutination: reduces number of infectious units
Opsonization: coating antigen with antibody to enhance phagocytosis
Neutralization: blocks adhesion of bacteria and viruses to the mucosa
Activation of Complement: causes inflammation and cell lysis… antibodies attached by target cell cause destruction by macrophages, eosinophils, and NK cells
List and describe the different classes of vaccines. Which vaccine types generally provide the strongest immunity and why?
Live Attenuated Vaccines: weakened pathogen with reduced virulence and retains all of its antigenic properties (provides the strongest immunity)
Inactivated Killed Vaccines: safer than live vaccines but require repeated booster doses which induce mostly humoral immunity
Subunit Vaccines: use antigenic fragments to stimulate an immune response (ex. recombinant vaccines, toxoids, etc.)
Polysaccharide Vaccines: made from molecules in pathogen’s capsule (not very immunogenic)
Conjugated Vaccines: used for diseases in children with poor immune response to capsular polysaccharides
Nucleic Acid (DNA) Vaccines: Naked DNA is injected into recipient cells & produces the protein antigen encoded in the DNA
Recombinant Vector Vaccines: use avirulent viruses as a delivery systems to deliver genes codings for antigens (are genetically modified)
How do the COVID vaccines vary in terms of their composition/construction and function?
Pfizer/Moderna Vaccine:
-Nucleic acid vaccine
-mRNA encodes a full-length spike glycoprotein (the target of neutralizing antibodies that are believed to inactivate the virus)
J&J Vaccines:
-Viral vector vaccine
-Been genetically modified so it can no longer replicate in humans and cause diseases
