What is the immune system?
The set of cellular and molecular mechanisms protecting the organism.
How does the immune system avoid attacking the organism?
Through immune tolerance.
What role does the immune system play in tissue repair?
It contributes to tissue repair.
How does the immune system protect against later attacks?
By immune memory.
Why is the intestinal microbiota beneficial?
Because it produces vitamins.
What risk increases if the intestinal microbiota is lost?
The risk of chronic disease increases.
What are examples of external aggressors in tissue injury?
Infectious agents, toxins, and trauma are external aggressors.
What are examples of internal aggressors in tissue injury?
Ischemia, degeneration, cancer, and cell death are internal aggressors.
What types of infectious agents can cause tissue injury?
Viruses, bacteria, or parasites can cause tissue injury.
Where do infectious agents multiply in the body?
They multiply intracellularly or extracellularly.
Can infectious agents be microscopic or macroscopic?
Yes, infectious agents may be microscopic or macroscopic.
What type of defense is innate immunity?
A broad, non-specific defense.
What do innate immunity receptors recognize?
Motifs shared by different pathogens or signs of cellular suffering.
What type of defense is adaptive immunity?
A specific, targeted defense.
Which cells mainly mediate adaptive immunity?
T and B lymphocytes.
What is one role of innate effectors in immunity?
They maintain tissue surveillance.
When do innate effectors respond to aggression?
Within the first minutes of aggression.
What is one function of adaptive immunity besides reinforcing innate defense?
It provides immune memory.
What does adaptive immunity maintain tolerance to?
Self and useful components such as the microbiota.
How soon does innate immunity appear after pathogen exposure?
Within minutes to hours.
How long does adaptive immunity take to develop after pathogen exposure?
Approximately 4 to 5 days to one week.
How long does effective elimination of a pathogen take?
Approximately 1 to 4 weeks.
How long can immune memory persist after pathogen exposure?
For months or years.
What characterizes the immune response on re-exposure to the same pathogen?
It is rapid and specific.
What can happen to the pathogen on re-exposure without clinical symptoms?
It may be eliminated by the immune response.
How do innate immune receptors differ from adaptive immune receptors?
Innate receptors are limited and invariant, adaptive receptors are hypervariable and individual-specific.
What is the frequency of adaptive lymphocytes with receptors for a useful pathogen?
About 1 in 100,000 cells initially express such receptors.
By how much can adaptive activation increase relevant effector cells?
It can multiply them by 100,000-fold or more.
How does combining innate and adaptive immunity strengthen defense?
It provides rapid broad protection plus delayed specific protection and memory.
Which organ produces lymphocytes and educates B cells?
The bone marrow produces lymphocytes and educates B cells.
Which organ educates T cells in primary lymphoid organs?
The thymus educates T cells.
Where do lymphocytes encounter antigen in the body?
In secondary lymphoid organs.
Name three secondary lymphoid organs where lymphocytes meet antigen.
Lymph nodes, Peyer’s patches, and the spleen.
What is the immune repertoire?
The complete set of T-cell and B-cell receptors recognizing antigens.
What percentage of developing adaptive immune cells die by apoptosis?
Approximately 95% die by apoptosis during receptor quality-control.
Where does a T-cell precursor complete differentiation and education?
In the thymus.
What happens to a mature naïve T cell after thymic education?
It circulates through secondary lymphoid organs and activates after antigen recognition.
What is the main role of CD4 T cells in immune responses?
They coordinate and orient immune responses.
What cytotoxic function do CD8 T cells perform?
They lyse infected or transformed cells.
What defines humoral immunity?
CD4 T cells activate B cells to produce antibodies against extracellular pathogens.
What characterizes cellular immunity?
CD8 T cells provide cytotoxicity against intracellular pathogens and collaborate with macrophages and natural killer cells.
How do CD4 T cells influence adaptive immunity?
They orient it toward either a humoral or cellular response.
What percentage of immune effectors are eliminated during clonal contraction?
Approximately 95%.
Test your knowledge with 21 questions on Temporal Organization of Immune Responses.
1. What best defines the immune system?
2. Which combination correctly describes the major missions of the immune system?
Review the complete course in the study sheet for Temporal Organization of Immune Responses.
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