Exam 3b Flashcards
What are infectious agents capable of doing to a host?
Damage or kill a host
What are pathogenic agents?
Agents that cause harm
What are the five major categories of infectious agents?
- Bacteria
- Viruses
- Fungi
- Protozoans
- Multicellular parasites
What are bacteria?
Single-celled prokaryotes
What are the types of bacterial shapes?
- Spherical (cocci)
- Rodlike (bacilli)
- Coiled (spirilla)
What are virulent bacteria capable of?
Causing serious illness
What are examples of virulent bacteria?
- Clostridium tetani (tetanus)
- Streptococcal bacteria (strep throat)
What are viruses composed of?
Pieces of DNA or RNA in a protein shell
How do viruses reproduce?
By entering a cell and directing it to make copies of nucleic acid and capsid
What are fungi?
Eukaryotic cells with membrane and cell wall
What diseases can fungi cause?
- Superficial diseases (e.g., ringworm)
- Mucosal infections (e.g., vaginal yeast infections)
- Internal infections (e.g., histoplasmosis)
What are protozoans?
Eukaryotic cells without a cell wall
What diseases are caused by protozoans?
- Malaria
- Trichomoniasis
Protozoan infections are parasitic diseases caused by single-celled organisms that can be found in humans, animals, plants, and fungi. They can be transmitted through contact with infected surfaces or substances, or by insect vectors like sandflies or bugs. The infections cause tissue damage that leads to disease.
What are multicellular parasites?
Nonmicroscopic organisms that take nourishment from their host
What are prions?
Fragments of infectious proteins that cause disease in nervous tissue
What disease can prions cause?
Variant Creutzfeldt-Jakob disease
Where are leukocytes formed?
In red bone marrow
What are the types of leukocytes?
- Granulocytes (neutrophils, eosinophils, basophils)
- Monocytes
- Lymphocytes (B-lymphocytes, T-lymphocytes, NK cells)
What are secondary lymphatic structures?
- Lymph nodes
- Spleen
- Tonsils
- MALT
- Lymphatic nodules
What are dendritic cells derived from?
Monocytes
What are cytokines?
Small proteins that regulate immune activity
What is innate immunity?
Immunity present at birth that protects against a variety of substances
What is adaptive immunity?
Acquired immunity that involves specific T- and B-lymphocytes
What characterizes innate immunity?
- Responds nonspecifically to harmful substances
- First line of defense is skin and mucosal membranes
- Includes internal processes like inflammation and fever
What are the physical barriers of innate immunity?
- Skin
- Mucous membranes
What cells are involved in phagocytosis?
- Neutrophils
- Macrophages
- Dendritic cells
What is the function of basophils and mast cells?
Promote inflammation
What triggers apoptosis in unwanted cells?
NK (natural killer) cells
What do eosinophils attack?
Multicellular parasites
What are pattern recognition receptors?
Receptors that recognize microbes as foreign
What are interferons?
Cytokines that impede viral spread
also referred to as IFN
What does the complement system do?
Works with antibodies to enhance immune response
What is opsonization?
Complement protein binds to pathogen, enhancing phagocytosis
Antibody opsonization is an immune process that tags pathogens with antibodies to mark them for destruction by phagocytes
What are the cardinal signs of inflammation?
- Redness
- Heat
- Swelling
- Pain
- Loss of function
What is fever (pyrexia)?
Abnormal body temperature elevation of 1°C or more from normal
What triggers the hypothalamus to raise the temperature set point during a fever?
Release of pyrogens
What is an antigen?
Substance that binds a T-lymphocyte or antibody
What is an immunogen?
Antigen that induces an immune response
What is immunogenicity?
Ability of an antigen to trigger an immune response
What are haptens?
Small molecules that become immunogenic when attached to a carrier molecule
What can lead to autoimmune disorders?
Immune system reacting to self-antigens as if they were foreign
Define immunogenicity.
Ability to trigger an immune response
What factors increase immunogenicity?
- Degree of foreignness
- Size
- Complexity
- Quantity
It is the ability of a substance to trigger an immune response in the body
What are haptens?
Too small to function as an antigen alone; become immunogenic when attached to a carrier molecule
Provide an example of a hapten.
Toxin in poison ivy
What accounts for hypersensitivity reactions?
- Pollen
- Drugs such as penicillin
- Food
- insect stings
Allergic Reactions
What is immune tolerance?
Lack of tolerance for specific self-antigen, causing immune response as if cells were foreign
What can cause immune response against self-antigens?
- Cross-reactivity
- Altered self-antigens
- Entering areas of immune privilege
Autoimmunity
occurs when the body’s immune system mistakenly attacks healthy cells and tissues as foreign
What are T- and B-lymphocytes?
Cells with unique receptor complexes that bind specific antigens
What is TCR?
T-cell receptor, the antigen receptor of T-lymphocytes
What is BCR?
B-cell receptor, the antigen receptor of B-lymphocytes
How do B-lymphocytes interact with antigens?
Make direct contact with antigen
How do T-lymphocytes interact with antigens?
Antigen is presented by another cell
Name the two types of T-lymphocyte coreceptors.
- CD4+ (Helper T-lymphocytes)
Activates other immune cells like macrophages and B cells to fight infections
- CD8+ (Cytotoxic T-lymphocytes)
Killer T
a type of white blood cell that plays a crucial role in the immune system by directly targeting and destroying infected or cancerous cells.
What do helper T-lymphocytes do?
Assist in cell-mediated, humoral, and innate immunity
What is the function of cytotoxic T-lymphocytes?
Release chemicals that destroy other cells
What is antigen presentation?
Cells display antigen on plasma membrane for T-cells to recognize
What are antigen-presenting cells (APCs)?
Immune cells that present antigens to both helper T-cells and cytotoxic T-cells
What is MHC?
Major histocompatibility complex
MHC molecules display peptide fragments for T-cell recognition, a vital process for destroying pathogens
The MHC also helps the immune system differentiate between self and non-self, and prevents it from attacking the body’s own cells
Where is MHC I found?
On all nucleated cells
Where is MHC II found?
On antigen-presenting cells (APCs)
What do MHC class I molecules display?
Fragments of proteins from endogenous sources
What do MHC class II molecules display?
Exogenous antigens processed into peptide fragments
What are the three main events in the life of a lymphocyte?
- Formation of lymphocytes
- Activation of lymphocytes
- Effector response
Where does lymphocyte formation occur?
In primary lymphatic structures (red marrow and thymus)
What happens during the activation of lymphocytes?
They are exposed to antigen and become activated, replicating to form identical lymphocytes
What is the effector response of T-lymphocytes?
Migrate to site of infection
What is the effector response of B-lymphocytes?
Stay in secondary lymphatic structure as plasma cells, synthesizing and releasing antibodies
Where do T-lymphocytes originate?
In red bone marrow
What is thymic selection?
Eliminates T-cells that do not bind MHC with antigen or bind self-antigens
What is positive selection in thymic selection?
the process where immature T cells (thymocytes) that can bind to self-MHC molecules, even weakly, are rescued from programmed cell death and allowed to mature, while those that cannot bind are eliminated
What is negative selection in thymic selection?
the process where T cells with a high affinity for self-antigens undergo apoptosis, preventing them from maturing and potentially causing autoimmune responses. This ensures the body’s immune system doesn’t attack its own tissue
What are regulatory T-lymphocytes (Tregs)?
CD4+ cells that inhibit immune response and function in tolerance
What is clonal selection?
Forming clones in response to an antigen, all with the same TCR or BCR
What is the antigen challenge?
First encounter between antigen and lymphocyte
What are the first signals for activation of helper T-lymphocytes?
Direct contact with MHC molecule of APC presenting exogenous antigen
What is the second signal for activation of helper T-lymphocytes?
Other receptors of APC and T-cell interact
What happens after helper T-lymphocytes are activated?
They proliferate forming clones and some become memory helper T-lymphocytes
What is the first signal for activation of cytotoxic T-lymphocytes?
Direct contact between TCR of cytotoxic T-cell and peptide fragment with MHC I molecule
What is the second signal for activation of cytotoxic T-lymphocytes?
IL-2 from helper T-cells binds to and stimulates cytotoxic T-lymphocytes
What happens after B-lymphocytes are activated?
They proliferate and differentiate, most into plasma cells that produce antibodies
What is lymphocyte recirculation?
Lymphocyte exits secondary lymphatic structure and circulates through blood and lymph
What mechanisms do lymphocytes use to eliminate antigens?
- Helper T-lymphocytes release IL-2 and other cytokines
- Cytotoxic T-lymphocytes destroy unhealthy cells
- Plasma cells produce antibodies
What is the structure of antibodies?
Y-shaped, composed of four polypeptide chains (two heavy and two light)
What are the five major classes of immunoglobulins?
- IgG
- IgM
- IgA
- IgD
- IgE
What is neutralization in terms of antibody function?
Antibody physically covers antigenic determinant of pathogen, making it ineffective
What is agglutination?
Antibody cross-links antigens of foreign cells causing clumping
What does the Fc region of antibodies do?
- Complement fixation
- Opsonization
- Activation of NK cells
What is active immunity?
Results from direct encounter with pathogen, forming memory cells
What is passive immunity?
Obtained from another individual, does not produce memory cells
What is class switching in antibodies?
When a plasma cell changes the type of antibody it produces
What is the antibody titer?
Circulating blood concentration of antibody against a specific antigen
What is an acute hypersensitivity?
Exaggerated response of immune system to a noninfectious substance, occurring within seconds
What is a delayed hypersensitivity?
Occurs within 1 to 3 days and involves cell-mediated immunity
What are acute hypersensitivities?
Acute hypersensitivities occur within seconds
These hypersensitivities are characterized by an immediate immune response.
What are subacute hypersensitivities?
Subacute hypersensitivities occur within 1 to 3 hours
They involve a delayed immune response compared to acute hypersensitivities.
What type of immunity is involved in both acute and subacute hypersensitivities?
Humoral immunity
This type of immunity involves antibodies produced by B cells.
What are delayed hypersensitivities?
Delayed hypersensitivities occur within 1 to 3 days
These involve a slower immune response mediated by T cells.
What type of immunity is involved in delayed hypersensitivities?
Cell-mediated immunity
This type of immunity involves T lymphocytes and does not rely on antibodies.
What is acute hypersensitivity also known as?
Allergy
Allergies are exaggerated immune responses to noninfectious substances.
What is an allergen?
A noninfectious substance that triggers an exaggerated immune response
Examples include pollen, latex, and peanuts.
What are the phases involved in acute hypersensitivity?
Sensitization, activation, and effector phases
Each phase contributes to the overall allergic response.
What symptoms may acute hypersensitivity cause?
- Runny nose and watery eyes
- Labored breathing and coughing (allergic asthma)
- Red welts and itchy skin (hives)
- Vomiting and diarrhea
- Systemic vasodilation and inflammation
These symptoms can vary widely among individuals.
What can severe acute hypersensitivity lead to?
Anaphylactic shock
This is a life-threatening allergic reaction requiring immediate medical attention.
What is AIDS?
Acquired immunodeficiency syndrome
AIDS is a condition resulting from the human immunodeficiency virus (HIV).
What does HIV infect and destroy?
Helper T-lymphocytes
These cells are crucial for the immune response.
How is HIV transmitted?
- Intercourse
- Needle sharing
- Breastfeeding
Understanding transmission routes is key for prevention.
When is a diagnosis of AIDS made?
When helper T-lymphocyte count drops below 200 cells per cubic milliliter
This count indicates severe immunodeficiency.
What typically causes death in AIDS patients?
Opportunistic infections or cancer
These individuals are highly susceptible due to weakened immune systems.
What is a prevention method for HIV/AIDS?
Safe sex
Practicing safe sex reduces the risk of transmission.
What type of cells are bacteria made up of?
prokaryotic
Are viruses smaller or larger than bacterial cells?
smaller
What type of diseases are caused by mycoses?
fungal disease
what are the three types of granulocytes?
eosinophils
basophils
neutrophils
What small proteins serve as a means of communication between immune system cells?
cytokines
What are two characteristics of bacteria?
bacteria are single-celled orgnaisms
1-2 micrometers in size
lack membrane-bound organelles like a nucleus
what immune cell is part of innate immunity?
natural killer (NK) cell
Viruses must enter a cell to reproduce. They are called obligate intracellular ____.
parasites
Is innate immunity specific or nonspecific?
nonspecific
means it responds in a general way to a wide range of pathogens, without targeting any specific antigen, unlike the adaptive immune system which is specific
fungi are composed of what type of cells?
eukaryotic
what are the hairs in the nose that trap microbes called?
vibrissae
natural killer cells are a type of _____.
lymphocyte
T or F: acid is produced by the digestive and reproductive systems, aiding the immune system
True
vesicles with infectious agents that formed during phagocytosis merge with what?
lysosomes
what type of immunity do natural killer cells provide?
nonspecific
the first line of defense of innate immunity includes what?
the skin
antimicrobial proteins are part of what immune system?
the innate immune system
Hair-like extensions of plasma membranes that in the respiratory system, function to sweep mucus upward so that it can be expectorated or swallowed are _____.
cilia
our salivary glands produce what antimicrobial enzyme?
lysozyme
where are complement proteins synthesized
the liver
what is the order of events of inflammation?
1-Release of chemicals
2-Vasodilation
3-Recruitment of immune cells
4-Delivery of plasma proteins
examples of antimicrobial proteins of the innate immune system are what?
interferons (IFN)
During inflammation, increased fluid, protein, and immune cells leave the capillaries and enter the interstitial space. This material is called ____.
exudate
what causes redness and heat in an inflamed area?
increased blood flow
what type of pathogen do interferons mainly target?
viruses
what is an abnormal elevation of core body temperature?
fever (aka pyrexia)
the compliment system is made of 30 different what?
proteins
B-cells are primarily involved in ______-mediated immunity.
antibody
antigens are usually ____
a protein or large polysaccharide
During inflammation, more fluid immune cells, and proteins ______ the capillaries
leave
when the body fails to distinguish between foreign antigens and self-antigens, what kind of disorders occur?
immune disorders
redness, heat, and swelling are cardinal signs of what?
inflammation
Helper T-lymphocytes are also referred to as ____
CD4 cells
identify the antigen-presenting cells
dendritic cells
macrophages
b-lymphocytes
antibody mediated immunity is also called what?
humoral immunity
Positive selection tests to see if the ______ of a T-lymphocyte can recognize and bind to an MHC molecule
TCR
CD8 cells are also called what?
cytotoxic T-cells
where are foreign antigens found in the blood usually taken?
spleen
antigen presentation is the display of an antigen on a cells what?
plasma membrane
B-lymphocytes and T-lymphocytes identify pathogenic organisms by recognizing their what?
antigens
A helper T cell is first stimulated by binding to antigen presented on _____
an MHC class II molecule presented by an APC
T-lymphocytes that can bind with thymic epithelial cells that have MHC molecules have passed a test called what?
positive selection
what are the events of b cell activation in order?
1) b cell binds free antigen
2) b cell engulfs antigen and presents it to a T helper cell
3) activated helper T cell releases IL-4
4) b cell proliferates
lymphocytes usually first encounter therefore an antigen in ____
a secondary lymphatic structure
Lymphocytes do not stay in secondary lymph structures permanently but move out after several days. This process is referred to as lymphocyte ____
lymphocyte migration
identify the antigen-presenting cells
macrophages
b-lymphocytes
dendritic cells
what is the effector response of cytotoxic T cells?
destroys infected cells via apoptosis
what is the effector response of plasma cell?
produces antibodies
what is the effector response of helper T cell?
releases interleukins and cytokines to stimulate other cells
Activated helper T cells release what 2 things to stimulate other immune cells?
cytokines
interleukins
what are the events of activation of a t helper cell in order?
1) APC engulfs antigen and presents it on an MHC class II molecule
2) helper T cell binds APC
3) helper T cell secretes IL-2
4) helper T cell proliferates
a b cell is first stimulated by what?
antigens outside of cells
What increases the odds that a specific lymphocyte will encounter its specific antigen?
lymphocyte recirculation
what is the circulating concentration of antibodies against a specific antigen called?
antibody titer
The various ways that activated lymphocytes combat an antigen are collectively referred to as the ______ response.
effector response
what are antibodies?
immunoglobulins
activated helper t cells are required to activate what?
cytotoxic T cells
b cells
what is an antibody monomer made of?
two heavy chains and two light chains
a helper t cell is first stimulated by binding to antigen presented on what?
an MHC class II molecule presented by an APC
If the wrong blood type is given to a patient, their red blood cells clump up because antibodies cross-link them in a process known as _____
aggulation
what class of immunoglobulin has a half life in the blood of 23 days?
IgG (immunoglobulin G)
the concentration of antibodies against a specific antigen in the blood is known as the antibody ____
antibody titer
what does IgG usually exist as?
a monomer
what kind of antigens do antibodies normally target?
specific antigens
What class of immunoglobulin is most effective at causing agglutination of cells and binding complement?
IgM
A Y-shaped immunoglobulin molecule is made of four polypeptide chains and referred to as a(n) _______
antibody monomer
what is the half life of IgA in the blood?
5.5 days
When antibodies completely cover the surface of a virus so it can no longer infect a cell, it is said to be ______.
neutralized
what is the first exposure to an antigen called?
antigen challenge
Identify the class of immunoglobulin that is produced during an allergic reaction and has a half-life in the blood of 2 days.
IgE
antibody concentration in the blood is also known as what?
antibody titer
What are true statements regarding IgG?
it can neutralize snake venom
predominant antibody in the blood
it can cross the placenta
what type of immunity lasts longer?
active immunity
is IgM more or less versatile than IgG in its biological functions?
less
immunity due to a vaccine is an example of what type of immunity?
artificially acquired active immunity
Identify the class of immunoglobulin that is found in mucus, saliva, tears, and breast milk.
IgA
Identify the type of immunity that is passed from mother to baby through the placenta.
naturally acquired passive immunity
The memory response of the immune system is also called the ______ response.
anamnestic response
Identify the type of hypersensitivity that occurs within 1 to 3 hours of exposure.
subacute hypersensitivities
antibody titer is a measure of what?
immunologic memory
T or F: active immunity may result from direct exposure to an antigen
True
T or F: active immunity includes the development of memory cells
True
being exposed to the cold virus and subsequently getting the cold results in ____
naturally acquired active immunity
immunity obtained from another individual is called what?
passive immunity
Which type of hypersensitivity occurs within seconds following exposure to the antigen?
acute
IgE is involved in what?
acute hypersensitivities
