Which of the following is a barrier against pathogens provided by the
skin?
dessication
Although interferons have several effects, they are particularly
useful
against infections with which type of pathogen?
viruses
Which organelle do phagocytes use to digest engulfed particles?
lysosome
Which innate immune system component uses MHC I
molecules
directly in its defense strategy?
neutrophils
Which of the following is both a phagocyte and an antigen-presenting
cell?
macrophage
Which immune cells bind MHC molecules on APCs via CD8 coreceptors on their cell surfaces?
CTLs
What “self” pattern is identified by NK cells?
missing self
The acquired ability to prevent an unnecessary or destructive immune reaction to a harmless foreign particle, such as a food protein, is called ________.
immune tolerance
A memory B cell can differentiate upon reexposure to a pathogen of which cell type?
plasma cell
Foreign particles circulating in the blood are filtered by the
spleen
The structure of an antibody is similar to the extracellular component of which receptor?
BCR
The first antibody class to appear in the serum in response to a newly encountered pathogen is ________.
IgM
What is the most abundant antibody class detected in the serum upon reexposure to a pathogen or in reaction to a vaccine?
IgG
Breastfed infants typically are resistant to disease because of
passive immunity
Allergy to pollen is classified as
immediate hypersensitivity
A potential cause of acquired autoimmunity is ________
molecular mimicry
Autoantibodies are probably involved in:
systemic lupus erythematosus
Which of the following diseases is not due to autoimmunity?
HIV/AIDS
Mast cell
located in: connective tissues, mucous membranes
characteristics: dilates blood vessels and induces inflammation through release of histamines and heparin, recruits macrophages and neutrophils. involved in wound healing and defense against pathogen, but can also be responsible for allergic reactions
Macrophage
located in: migrates from blood vessels into tissues
characteristics: phagocytic cell that consumes foreign pathogens and cancer cells. stimulates response of other immune cells.
Natural Killer cell
located in: circulates in blood and migrates into tissues
characteristics: kills tumor cells and virus infected cells.
dendritic cell
located in: present in epithelial tissue, including skin, lung, and tissues of the digestive tract. migrates to lymph nodes upon activation
characteristics: presents antigens on its surface, thereby triggering adaptive immunity.
monocyte
located in: stored in spleen, moves through blood vessels to infected tissues
characteristics: differentiates into macrophages and dendritic cells in response to inflammation
neutrophil
located in: migrates from blood vessels into tissues
characteristics: first responders at the site of infection or trauma, this abundant phagocytic cell represents 50-60 percent of all leukocytes. releases toxins that kill or inhibit bacteria and fungi and recruits other immune cells to the site of infection
basophil
located in: circulated in blood and migrates to tissues
characteristic: responsible for defense against parasites. releases histamines that cause inflammation and may be responsible for allergic reactions.
eosinophil
located in: circulated in blood and migrates in tissues
Characteristics: releases toxins that kill bacteria and parasites but also causes tissue damage
IgA
Found in mucous, saliva, tears, and breast milk. Protects against pathogens.
IgD
Part of the B cell receptor. Activates basophils and mast cells.
IgE
Protects against parasitic worms. Responsible for allergic reactions.
IgG
Secreted by plasma cells in the blood. Able to cross the placenta into the fetus.
IgM
May be attached to the surface of a B cell or secreted into the blood. Responsible for early stages of immunity.
IgE-mediated hypersensitivity (type I)
IgE is BOUND to mast cells via its Fc portion. When an allergen binds to these antibodies, crosslinking of IgE induces degranulation.
Caused localized and systemic anaphylaxis, seasonal allergies including hay fever, food allergies such as those to shellfish and peanuts, hives and eczema.
IgG-mediated cytotoxic hypersensitivity (type II)
Cells are destroyed by bound antibody, either by activation of complement or by a cytotoxic T cell with an Fc receptor for the antibody (ADCC)
Red blood cells destroyed by complement and antibody during a transfusion of mismatched blood type of during erythroblastosis fetalis
Immune complex-mediated hypersensitivity (type III)
Antigen-antibody complexes are deposited in tissues, causing activation of complement, which attracts neutrophils to the site
Most common forms of immune complex disease are seen in glomerulonephritis, rheumatoid arthritis, and systemic lupus erythematosus.
Cell-Mediated Hypersensitivity (type IV)
Th1 cells secrete cytokines, which activate macrophages and cytotoxic T cells and can cause macrophage accumulation at the site.
Most common forms are contact dermatitis, tuberculin reaction, autoimmune diseases such as diabetes mellitus type I, multiple sclerosis, and rheumatoid arthritis.
Cells found in the innate immune system
Hematopoietic cells: macrophages, dendritic cells, mast cells, neutrophils, basophils, eosinophils, natural killer cells, T cells
Non-hematopoietic cells: epithelial cells (skin, airways, gastrointestinal tract)
Cells found in the adaptive immune system
Hematopoietic cells: T cells, B cells
Molecules in the Innate immune system
Cytokines, complement, proteins and glycoprotein
Molecules in the adaptive immune system
Antibodies (IgG, IgM, IgE, IgD, IgA), cytokines
the response time of the innate immune system is
immediate
the response time of the adaptive immune system is
delayed by hours to days
The immunologic memory of the innate immune system is
None, responses are the same with each exposure
the immunologic memory of the adaptive immune system is
the responsiveness is enhanced by repeated antigen exposure
Complement cascade
- 20 types of proteins from liver and macrophages
- opsonization
neutralization
antibodies prevent a virus or toxic protein from binding their target
opsonization
a pathogen tagged by antibodies is consumed by a macrophage or neutrophil
complement activation
antibodies attached to the surface of a pathogen cell activate the complement system `
affinity
the strength of a single antibody-antigen interaction. Each IgG antigen binding site typically has high affinity for its target
avidity
refers to the strength of all interactions combined. IgM typically has low affinity antigen binding sites, but there are ten of them, so avidity is high
immunoglobulins characteristics
-Made of four protein chains; two identical light chains; two identical heavy chains; chains are joined by disulfide links
- Variable regions
-Constant regions
Naturally acquired – adaptive immunity
Active: antigens enter the body naturally; body induces antibodies and specialized lymphocytes
Passive: antibodies pass from mother to fetus via placenta or to infant via the mother’s milk
Artificially acquired – adaptive immunity
Active: antigens are introduced in vaccines; body produces antibodies and specialized lymphocytes
Passive: preformed antibodies in immune serum are introduced by injection
Humoral/antibody mediated immunity
- mediated by B cells (memory, affector)
- antibodies
-dendritic cells
-APC
- mature in bone marrow
Cellular/ cell mediated immunity
-mediated by T cells (antigen presenting cells; macrophages and dendritic cells)
-T lymphocytes: helper (CD4), cytotoxic (CD8), memory, suppressor, NK
-Mature in Thymus
MHC I
binds peptide fragments derived from pathogens and display them on the cell surface for recognition by the appropriate T cells.
cell surface recognition elements expressed on virtually all somatic cells
PAMPS
signature molecules expressed by pathogens, recognized by PRRs
PRRs
detect distinct evolutionarily conserved structures on pathogens (PAMPS)
recognize cellular injury as well
The first responders at the site of infection are
neutrophils
principal phagocytic cell
macrophage