Immune System Flashcards
What are the components of the immune system?
Cells, plasma proteins, and secreted products.
Define the term ‘cytokines’.
Small, soluble proteins produced by immune cells.
What role do cytokines play in the immune system?
Regulate and facilitate immune activity.
Define ‘innate immunity’.
Defense mechanisms we are born with.
Define ‘adaptive immunity’.
Specific immune response involving T-lymphocytes and B-lymphocytes.
What constitutes the first line of defense in the immune system?
Intact skin and mucous membranes.
Which cells comprise the second tier of innate defenses?
Neutrophils, macrophages, dendritic cells, basophils, mast cells, eosinophils, and natural killer cells.
Which of the following cells are phagocytic?
Neutrophils, macrophages, dendritic cells.
What are antimicrobial proteins?
Proteins that help destroy pathogens.
What is the function of interferons?
Interferons are involved in antiviral activity and immune regulation.
Define inflammation.
A localized response to injury characterized by redness, heat, swelling, and pain.
What are the cardinal signs of inflammation?
- Redness * Heat * Swelling * Pain
Define diapedesis.
The movement of immune cells out of blood vessels.
What is exudate?
Fluid that leaks out of blood vessels during inflammation.
What is a fever?
An elevation of body temperature above normal.
Define pyrogen.
Substances that induce fever.
What is defervescence?
The process of returning to normal body temperature after a fever.
What are the benefits of a fever?
- Inhibits pathogen growth * Enhances immune response
What are the two types of adaptive immunity?
- Cell-mediated immunity * Antibody-mediated immunity
Define antigen.
A substance that induces an immune response.
What is the difference between a self-antigen and a foreign antigen?
Self-antigens belong to the body; foreign antigens do not.
What is an immunogen?
A complete antigen that can provoke an immune response.
What is a hapten?
A partial antigen that cannot provoke an immune response alone.
Define autoimmunity.
An immune response against the body’s own tissues.
What are the types of autoimmune disorders?
Examples include rheumatoid arthritis, lupus, and multiple sclerosis.
Describe the general structure of T-lymphocytes and B-lymphocytes.
T-lymphocytes have T-cell receptors; B-lymphocytes have B-cell receptors.
What role do T-lymphocyte receptors play?
They recognize specific antigens presented by MHC proteins.
What is the major histocompatibility complex (MHC)?
A set of proteins that present antigens to T-lymphocytes.
What are the two classes of MHC proteins?
- MHC I * MHC II
What is the function of MHC I proteins?
Present endogenous antigens to cytotoxic T-cells.
What is the function of MHC II proteins?
Present exogenous antigens to helper T-cells.
Explain positive selection in T-lymphocytes.
Process that ensures T-cells recognize self-MHC.
Explain negative selection in T-lymphocytes.
Eliminates T-cells that strongly bind self-antigens.
What is the role of helper T-lymphocytes?
Activate B-lymphocytes and cytotoxic T-lymphocytes.
What is the role of cytotoxic T-lymphocytes?
Destroy infected or cancerous cells.
What is costimulation?
A second signal required for full activation of T-lymphocytes and B-lymphocytes.
What are the five major classes of antibodies?
- IgG * IgM * IgA * IgD * IgE
What are the immunologic actions of antibodies?
- Neutralization * Agglutination * Precipitation * Opsonization
Define immunologic memory.
The ability of the immune system to remember past infections.
What is the difference between primary and secondary antigenic exposure?
Primary exposure has a slower response; secondary is faster and stronger.
What are vaccinations?
Inoculations that stimulate an immune response.
Define active immunity.
Immunity resulting from exposure to an antigen.
Define passive immunity.
Immunity acquired through antibodies from another source.
What is hypersensitivity?
An exaggerated immune response to an antigen.
What are the different types of hypersensitivity reactions?
- Type I (allergic) * Type II (cytotoxic) * Type III (immune complex) * Type IV (delayed)
What is HIV?
A virus that attacks the immune system, leading to AIDS.
What is AIDS?
Acquired Immunodeficiency Syndrome caused by HIV.
What do eosinophils release to combat parasites?
Eosinophils release substances that are lethal to the parasites, such as enzymes, reactive oxygen-containing compounds, and neurotoxins.
How do eosinophils destroy multicellular organisms?
Eosinophils release proteins that form transmembrane pores.
What role do eosinophils play in allergies and asthma?
Eosinophils participate in the immune response associated with allergy and asthma and engage in phagocytosis of antigen–antibody complexes.
What receptors do innate immune cells use to recognize foreign microbes?
Pattern recognition receptors, such as toll-like receptors (TLRs).
What are the two categories of antimicrobial proteins in the innate immune system?
- Interferons (IFNs)
- Complement
What is the function of interferons?
Interferons serve as a nonspecific defense mechanism against the spread of viral infection.
What process do interferons inhibit?
The process of pathogen replication in our cells.
What is the complement system?
A group of at least 30 antimicrobial plasma proteins produced by the liver and released into the blood.
What are the defense mechanisms mediated by the complement system?
- Increased inflammation
- Opsonization
- Cytolysis through membrane attack complex (MAC)
- Linking antigen–antibody complexes to erythrocytes
What is inflammation?
An immediate, local, nonspecific event that occurs in vascularized tissue in response to various stimuli.
What are the cardinal signs of inflammation?
- Redness
- Heat
- Swelling
- Pain
- Loss of function
What is pus?
An exudate containing destroyed pathogens, dead white blood cells, macrophages, and cellular debris.
What is an abscess?
An accumulation of pus in a walled-off area.
What is the effect of applying ice for acute inflammation?
Ice serves to vasoconstrict blood vessels and numbs the area, decreasing the inflammatory response.
What characterizes chronic inflammation?
Inflammation that continues for longer than 2 weeks.
What are pyrogens?
Substances that produce a fever, such as IL-1, IL-6, TNF-α, and toxins from infectious agents.
What are the three events of fever?
- Onset
- Stadium
- Defervescence
What is an antigen?
A substance that is different from molecules of the body and binds to a component of adaptive immunity.
What is immunogenicity?
The ability of an antigen to induce an immune response.
What are haptens?
Substances that are too small to function as an antigen alone but become antigenic when attached to a host molecule.
What are autoimmune disorders?
Conditions where the immune system does not have tolerance for a specific self-antigen and initiates an immune response to it.
What is the role of antigen-presenting cells (APCs)?
APCs communicate the presence of antigen to both helper T-lymphocytes and cytotoxic T-lymphocytes.
What distinguishes helper T-lymphocytes?
They contain the CD4 protein.
What do cytotoxic T-lymphocytes release?
Chemicals that destroy cells.
What is the function of memory T-cells?
They cause a more rapid response to an antigen upon future contacts.
What is the major histocompatibility complex (MHC)?
A specialized transmembrane protein required for antigen presentation.
Which cells function as APCs?
Dendritic cells, macrophages, and B-lymphocytes.
Where are MHC class I molecules presented?
On all nucleated cells.
What do APCs display?
Both MHC class I and MHC class II molecules.
What are MHC class I molecules?
Glycoproteins that present peptide fragments from within the cell to the plasma membrane.
What is the endogenous pathway?
The process by which MHC class I molecules display peptide fragments from endogenous proteins.
What distinguishes healthy self-cells from infected cells?
The display of MHC class I molecules with self-peptide fragments or nonself-peptide fragments.
What do MHC class II molecules present?
Fragments of antigens that have been engulfed by APCs.
What is the exogenous pathway?
The process by which APCs digest exogenous antigens into peptide fragments and display them on MHC class II molecules.
What is the significance of MHC molecules in organ transplants?
MHC molecules of transplanted tissue may be regarded as foreign by the host’s immune system.
What is the purpose of immunosuppressive drugs after a transplant?
To prevent the host’s immune system from destroying the transplanted organ.
What are the primary lymphatic structures for lymphocyte formation and maturation?
Red bone marrow and thymus.
How do lymphocytes become activated?
Upon their first exposure to the antigen they bind.
What is thymic selection?
The process by which the thymus selects T-lymphocytes for immunocompetence.
What happens during positive selection of T-lymphocytes?
T-lymphocytes that can bind MHC are selected; those that cannot are eliminated.
What is negative selection in T-lymphocyte development?
The elimination of T-cells that bind to self-antigens presented by MHC molecules.
What is self-tolerance?
The state in which cells ignore self-antigens.
What differentiates helper T-lymphocytes from cytotoxic T-lymphocytes?
Helper T-lymphocytes retain CD4 protein, while cytotoxic T-lymphocytes retain CD8 protein.
What is the function of regulatory T-cells (Tregs)?
To release inhibitory chemicals that turn off immune responses.
What is the first stimulation for the activation of helper T-lymphocytes?
Direct physical contact between an APC and a helper T-lymphocyte.
What is the role of interleukin 2 (IL-2) in T-lymphocyte activation?
It acts as an autocrine hormone to further stimulate the helper T-lymphocyte.
What is required for B-lymphocyte activation?
Two signals: antigen binding to BCR and interaction with helper T-lymphocytes.
What do activated B-lymphocytes differentiate into?
Plasma cells and memory B-lymphocytes.
What is lymphocyte recirculation?
The process by which lymphocytes exit secondary lymphatic structures and circulate through the blood.
What do antibodies do?
Bind and immobilize specific antigens, causing their elimination by other immune cells.
What is an antibody titer?
The circulating blood concentration of antibody against a specific antigen.
What is neutralization in the context of antibody function?
When an antibody physically covers the antigenic determinant.
What do antibodies do upon binding to specific antigens?
They bind and immobilize specific antigens and ultimately cause their elimination by other immune cells.
List the actions of antibodies following antigen binding.
- Neutralization
- Agglutination
- Precipitation
- Complement fixation
- Opsonization
- Triggering NK cell activity
What occurs during neutralization by antibodies?
An antibody physically covers the antigenic determinant of a pathogen to render it ineffective.
What is agglutination in the context of antibody action?
Antibodies cross-link antigens of foreign cells, causing them to clump.
Define precipitation as an action of antibodies.
Antibodies cross-link soluble antigens in the blood, causing them to become insoluble and precipitate out of solution.
What is complement fixation?
The Fc region of an antibody activates the complement system through the classical pathway.
What role does opsonization play in antibody action?
The Fc region of an antibody makes the antigen more attractive to phagocytic cells.
What is the function of IgG?
IgG is present in lymph, cerebrospinal fluid, serous fluid, and peritoneal fluid, and it can cross the placenta.
What percentage of antibodies are IgG?
75%–85%.
Where is IgM primarily found and what is its function?
IgM is found mostly in the blood and is very efficient at agglutination; it is responsible for rejection of mismatched blood.
What is the primary role of IgA?
IgA is found in areas exposed to the environment and is produced in mucus, saliva, tears, and breast milk, being especially effective at agglutination.
What is the function of IgD?
IgD functions as the antigen-specific B-lymphocyte receptor, along with the monomer form of IgM.
What is IgE associated with?
IgE is generally formed during allergic reactions and parasitic infections, causing release of products from basophils and mast cells.
What is class switching in the context of antibodies?
The process of changing the class of antibody produced by a plasma cell.
What is immunologic memory?
The development of immunologic memory is a central feature of adaptive immunity.
What occurs during the secondary response of the immune system?
Memory cells make contact more rapidly with the antigen and produce a powerful response.
How does the lag time differ between primary and secondary immune responses?
The lag time is longer in primary responses and much shorter in secondary responses due to memory lymphocytes.
What is antibody titer?
A measure of immunologic memory.
What characterizes the primary response to an antigen?
There is a lag or latent phase of 3–6 days before antibody production begins.
What is the difference between active and passive immunity?
- Active immunity results from direct encounter with a pathogen
- Passive immunity is obtained from another individual.
What is naturally acquired passive immunity?
Transfer of antibodies from mother to fetus across the placenta or to the baby in breast milk.
What is artificially acquired passive immunity?
Transfer of serum containing antibodies from one individual to another.
Do passive immunity and active immunity produce memory cells?
Active immunity produces memory cells; passive immunity does not.
What is a vaccine?
An attenuated or dead microorganism administered to a patient to stimulate the production of memory cells.
What is herd immunity?
Resistance within a population to contracting a contagious disease due to a high proportion of individuals being immune.
What percentage of vaccination is required for herd immunity?
Between 83% and 94%.
What is hypersensitivity?
An abnormal and exaggerated response of the immune system to an antigen.
What characterizes acute hypersensitivities?
They occur within seconds and involve IgE.
What are opportunistic infections?
Infections that thrive due to a compromised immune system; they account for up to 80% of AIDS-related deaths.
What is the significance of a helper T-lymphocyte count below 200 cells/mm3?
It is a criterion for diagnosing HIV as AIDS.
What is HAART?
Highly active antiretroviral therapy used to treat HIV.
Fill in the blank: ______ is a life-threatening condition caused by HIV.
AIDS
