Chapter 11_2 flashcards

Question 1

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Answer 1

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Question 2

Immune System: Primary Function

Answer 2

A complex defense mechanism that protects humans from injurious environmental agents by deciphering “self” versus “non-self” substances. Non-self substances (foreign antigens) are targeted for destruction.

Question 3

Innate Immunity: Definition & Key Components

Answer 3

The body’s first and immediate, non-specific line of defense. Components include: natural anatomical barriers (skin, mucous membranes), normal flora, white blood cells (WBCs like macrophages), and protective enzymes/chemicals (interferon, cytokines, hydrochloric acid).

Question 4

Adaptive Immunity: Definition & Key Characteristics

Answer 4

The immune system’s second line of defense, developed after exposure to antigens. Characteristics: specificity (targets specific antigens), memory (remembers antigens for future encounters), rapid and destructive response upon re-exposure. Involves B and T lymphocytes.

Question 5

Differentiate: Innate vs. Adaptive Immunity

Answer 5

Innate: Immediate, non-specific, no memory, first line of defense (barriers, phagocytes, NK cells). Adaptive: Delayed (develops after exposure), specific, has memory, second line of defense (B cells/antibodies, T cells).

Question 6

Antibody-Mediated (Humoral) Immunity: Mechanism

Answer 6

A type of adaptive immunity where B lymphocytes, upon encountering an antigen and with T-cell help, differentiate into plasma cells. Plasma cells produce and secrete specific proteins called immunoglobulins (antibodies) that neutralize or eliminate extracellular antigens.

Question 7

Cell-Mediated Immunity: Mechanism

Answer 7

A type of adaptive immunity mediated by T lymphocytes. CD8+ cytotoxic T cells directly kill infected host cells or tumor cells. CD4+ helper T cells coordinate the immune response by releasing cytokines that activate other immune cells (including B cells, macrophages, and other T cells).

Question 8

Compare: Antibody-Mediated vs. Cell-Mediated Immunity

Answer 8

Both are adaptive. Antibody-mediated (Humoral): B cells -> plasma cells -> antibodies; targets extracellular pathogens/toxins. Cell-mediated: T cells (CD4+ helper, CD8+ cytotoxic); CD8+ directly kill infected cells, CD4+ help activate/regulate immune responses.

Question 9

Types of Immune Dysfunction: Overview

Answer 9

1. Immunodeficiency: Weakened immune system unable to destroy foreign invaders. 2. Autoimmunity: Immune system fails to distinguish self from non-self, attacking body’s own tissues. 3. Hypersensitivity: Overreactive immune response against foreign invaders or self-antigens, causing tissue damage (e.g., allergies, transplant rejection).

Question 10

Antigen: Definition

Answer 10

Any substance, usually foreign, that is recognized by the immune system as non-self and is capable of eliciting an immune response, such as the production of antibodies or the activation of T lymphocytes.

Question 11

Major Histocompatibility Complexes (MHCs) / Human Leukocyte Antigens (HLAs)

Answer 11

Surface proteins found on nearly all human cells that present antigen fragments to T cells. They allow the adaptive immune system to distinguish between “self” (host cells) and “non-self” (foreign or infected cells). Crucial for antigen presentation and immune recognition.

Question 12

Monocyte-Macrophages: Origin & Functions

Answer 12

Macrophages arise from monocytes (a type of WBC) that migrate from peripheral circulation into tissues. Functions: Phagocytosis of debris/antigens, antigen presentation to T cells, mediation of innate immunity, cytokine production, breakdown of antigens with secretory products (hydrolytic enzymes, TNF-alpha, ILs).

Question 13

Cytokines: Definition & General Roles

Answer 13

Inflammatory mediators produced mainly by WBCs (macrophages, lymphocytes). Roles: Promote leukocyte recruitment, regulate lymphocyte growth/activation/differentiation, activate macrophages, stimulate hematopoiesis (new blood cell production). Examples: TNF-alpha, interleukins (ILs).

Question 14

Natural Killer (NK) Cells: Role in Immunity

Answer 14

A type of lymphocyte that is part of the innate immune response. NK cells act as a first line of defense by directly destroying tumor cells and virus-infected cells without prior sensitization or antigen presentation via MHC.

Question 15

Lymphocytes: Origin & Maturation

Answer 15

Primary cells of adaptive immunity. Originate from stem cells in the bone marrow in immature form.
T lymphocytes (T cells): Mature in the thymus gland.
B lymphocytes (B cells): Mature in the bone marrow, spleen, and lymph nodes.

Question 16

T Lymphocytes (T cells): General Role & Maturation Site

Answer 16

Key players in cell-mediated adaptive immunity. Mature in the thymus gland. Differentiate into various subtypes, including CD4+ helper T cells and CD8+ cytotoxic T cells.

Question 17

B Lymphocytes (B cells): General Role & Maturation Sites

Answer 17

Key players in antibody-mediated (humoral) adaptive immunity. Mature in bone marrow, spleen, and lymph nodes. When activated by antigen (with T-cell help), they differentiate into plasma cells (antibody-producing) and memory B cells.

Question 18

CD4+ Cells (T Helper Cells): Functions

Answer 18

A type of T lymphocyte that plays a central role in orchestrating the immune response. They recognize antigens presented by APCs on MHC class II molecules. Functions: Help activate B cells to produce antibodies, enhance activity of cytotoxic T cells, activate macrophages, and release cytokines that regulate other immune cells. Main target of HIV.

Question 19

CD8+ Cells (Cytotoxic T Cells): Functions

Answer 19

A type of T lymphocyte that directly kills host cells infected with viruses or other intracellular pathogens, as well as tumor cells. They recognize antigens presented on MHC class I molecules on the surface of target cells.

Question 20

Antigen-Presenting Cells (APCs): Role & Examples

Answer 20

Cells that capture, process, and present antigens to T lymphocytes to initiate an adaptive immune response. Examples: Dendritic cells (most potent, broadest range of antigen attachment), macrophages, and B cells.

Question 21

Dendritic Cells: Description & Function

Answer 21

Potent APCs named for their fine dendritic cytoplasmic projections. Located in epidermis and mucous membranes (where antigens enter). They capture and process antigens, then migrate to lymph nodes to present them to T cells, initiating innate and adaptive responses by releasing cytokines.

Question 22

Plasma Cells: Origin & Function

Answer 22

Differentiated B lymphocytes that are specialized in producing and secreting large quantities of specific antibodies (immunoglobulins). They are the effector cells of humoral immunity.

Question 23

Immunoglobulins (Igs) / Antibodies: Definition & General Functions

Answer 23

Proteins produced by plasma cells in response to a specific antigen. Functions: Neutralize bacterial toxins, attack viruses, promote phagocytosis of bacteria, activate the complement system, and play a role in allergic reactions and immune regulation. Five main classes: IgM, IgG, IgA, IgE, IgD.

Question 24

Immunoglobulin M (IgM): Characteristics & Significance

Answer 24

Largest immunoglobulin (macroglobulin). The first antibody class produced during a primary immune response (earliest responder to infection). Effective in activating complement. Due to its large size, it generally does not cross the placenta.

Question 25

Immunoglobulin G (IgG): Characteristics & Significance

Answer 25

Most abundant immunoglobulin in the bloodstream and tissue fluids. The predominant antibody in the secondary immune response (amnestic response). Crosses the placenta, providing passive immunity to the fetus/newborn. Involved in opsonization, complement activation, and neutralization of toxins/viruses. Commonly involved in autoimmune diseases.

Question 26

Immunoglobulin A (IgA): Characteristics & Significance

Answer 26

The main immunoglobulin found in mucosal secretions (tears, saliva, nasal/respiratory secretions, GI fluid, breast milk). Provides localized protection on mucosal surfaces against pathogens. Also called secretory IgA.

Question 27

Immunoglobulin E (IgE): Characteristics & Significance

Answer 27

Present in very low concentrations in blood but rises significantly in allergic reactions and parasitic infections. Binds to high-affinity receptors on mast cells and basophils, triggering release of histamine and other mediators upon antigen binding. Abundant in skin, mucous membranes, respiratory tract.

Question 28

Immunoglobulin D (IgD): Characteristics & Significance

Answer 28

Found in small amounts in serum, primarily located on the surface of naive B lymphocytes, where it functions as an antigen receptor involved in B cell activation. Also binds to basophils and mast cells in hypersensitivity reactions.

Question 29

Primary Immune Response: Description

Answer 29

The immune response that occurs upon the first exposure to a specific antigen. Characterized by a lag phase (5-7 days for IgM to be detected) while B cells are activated and differentiate into plasma cells. IgM is the predominant antibody produced initially.

Question 30

Secondary (Amnestic) Immune Response: Description

Answer 30

The immune response that occurs upon subsequent exposures to the same antigen. It is faster, stronger, and more prolonged than the primary response due to the presence of memory B and T cells. IgG is the predominant antibody produced.

Question 31

Active Acquired Adaptive Immunity: Definition & Examples

Answer 31

Immunity developed by an individual's own immune system after exposure to an antigen. This can occur through natural infection (contracting the disease) or through vaccination. Results in long-lasting protection due to the formation of memory cells.

Question 32

Passive Acquired Adaptive Immunity: Definition & Examples

Answer 32

Immunity acquired by receiving pre-formed antibodies from another source, rather than producing them oneself. Examples: Maternal IgG crossing the placenta to the fetus, IgA in breast milk, or administration of immune globulin (e.g., HBIg for hepatitis B exposure). Provides immediate but temporary protection (no memory cells formed).

Question 33

Vaccine: Definition & Purpose

Answer 33

A biological preparation containing a weakened (attenuated), killed (inactivated) pathogen, its toxins (toxoid), or one of its surface proteins (subunit/mRNA). Administered to stimulate the recipient's adaptive immune system to develop active acquired immunity and memory against a specific disease without causing the disease itself.

Question 34

Types of Vaccines Mentioned in Text

Answer 34

1. Live virus vaccines (inactivated/attenuated): Stimulate immune response but typically non-disease producing (e.g., oral poliovirus - though potential for mutation). 2. mRNA vaccines: Synthesized from viral pathogen's mRNA coding for a surface protein; patient's body manufactures the protein, triggering an immune response. 3. Bacterial vaccines: Derivatives of killed microorganisms or extracts of antigens or toxins. 4. Toxoids: Modified bacterial toxins that are non-disease producing but still antigenic (e.g., tetanus toxoid).

Question 35

Booster Vaccination: Purpose

Answer 35

An additional dose of a vaccine administered after the primary vaccination series to "boost" or restimulate the immune system's memory response, thereby increasing the level and duration of immunity against the specific antigen.

Question 36

Toxoid: Definition & Example

Answer 36

A type of vaccine made from a bacterial toxin that has been modified to be non-toxic but still capable of stimulating an immune response (i.e., it retains its antigenicity). Example: Tetanus toxoid vaccine.

Question 37

Vaccination / Immunization: Definition

Answer 37

Vaccination: The act of administering a vaccine. Immunization: The process by which an individual becomes protected against a disease through vaccination or prior infection, resulting in the development of active acquired immunity.

Question 38

Anergy Panel: Purpose & Interpretation

Answer 38

A test of general immunocompetence. It involves intradermal injection of common antigens (e.g., mumps, Candida) to which most individuals have been exposed. Positive reaction (redness, induration): Indicates immunocompetence. No reaction (anergy): Suggests a lack of immune responsiveness or immunodeficiency.

Question 39

Antibody Titer / Antibody Screening: Purpose & Interpretation

Answer 39

Laboratory tests used to measure the presence and level (titer) of specific antibodies (IgM and IgG) in the blood. Purpose: Confirm adequate immune protection against a particular antigen, diagnose current/past infection. Interpretation: Elevated IgM often indicates recent/current infection. Elevated IgG indicates past exposure and immunity.

Question 40

Allergy Testing: Methods Mentioned

Answer 40

1. Skin Tests: Measure IgE reaction to allergens by scratching/injecting small amounts into skin. Positive = redness, swelling, itching. 2. Serology Blood Tests (ELISA, RAST, ImmunoCAP IgE): Measure presence and amount of allergen-specific IgE in blood to evaluate severity of allergy.

Question 41

Hypersensitivity: General Definition

Answer 41

An exaggerated or inappropriate immune response to an antigen (allergen or autoantigen) that results in tissue damage and disease. Can involve cell-mediated or antibody-mediated mechanisms. Four main types (I, II, III, IV).

Question 42

Type I Immediate Hypersensitivity: Basic Mechanism

Answer 42

Rapidly developing immune reaction after IgE binds to mast cells and combines with antigen. Involves CD4 cells, IgE, eosinophils, and mast cells. Mast cell degranulation releases histamine and other mediators, causing allergy symptoms.

Question 43

Type II Cytotoxic Hypersensitivity: Basic Mechanism

Answer 43

Mediated by Igs (IgG or IgM) directed towards antigens present on cell surfaces. Antibodies target cells coated with antigen, leading to cell destruction via complement activation or phagocytosis.

Question 44

Type III Immune Complex Hypersensitivity: Basic Mechanism

Answer 44

Occurs when antigen combines with Ig (antibody) within circulation, forming immune complexes. These complexes deposit in tissues, triggering inflammation and organ dysfunction.

Question 45

Type IV Delayed Hypersensitivity: Basic Mechanism

Answer 45

Initiated by T lymphocytes (sensitized T cells) that have had previous exposure to an antigen. Reaction (inflammation, e.g., contact dermatitis) occurs days after re-exposure due to T cell cytokine release.

Question 46

Autoimmunity: General Definition

Answer 46

A state where the immune system fails to distinguish between self and non-self antigens, leading to an immune response against the body's own tissues and cells. Involves autoantibodies or autoreactive T cells.

Question 47

Immunodeficiency: General Definition

Answer 47

A state in which the immune system's ability to fight infectious disease and cancer is compromised or entirely absent. Can be primary (congenital) or secondary (acquired).

Question 48

Atopic Disorder: Definition

Answer 48

A term often used to describe a group of allergic conditions that are often inherited and include eczema (atopic dermatitis), allergic rhinitis (hay fever), and asthma. Associated with a tendency to produce IgE antibodies in response to common environmental allergens.

Question 49

HIV: Nature of Virus (Retrovirus, Lentivirus)

Answer 49

HIV (Human Immunodeficiency Virus) is a retrovirus, meaning its genetic material is RNA, and it uses the enzyme reverse transcriptase to convert its RNA into DNA within the host cell. It belongs to the *Lentivirus* genus, characterized by a long incubation period and slowly progressive disease course.

Question 50

Reverse Transcriptase (HIV Enzyme): Role

Answer 50

An enzyme unique to retroviruses like HIV. It converts the viral RNA genome into a double-stranded DNA copy, which can then be integrated into the host cell's DNA. A major target for antiretroviral drugs (NRTIs, NNRTIs).

Question 51

Integrase (HIV Enzyme): Role

Answer 51

An HIV enzyme that facilitates the insertion (integration) of the viral DNA (produced by reverse transcriptase) into the host cell's chromosomal DNA. This makes the infection permanent for that cell. A target for antiretroviral drugs (INSTIs).

Question 52

Protease (HIV Enzyme): Role

Answer 52

An HIV enzyme essential for the late stages of viral replication. It cleaves newly synthesized large viral polyproteins into smaller, functional proteins that are necessary for assembling mature, infectious virus particles. A target for antiretroviral drugs (PIs).

Question 53

CCR5 Receptor & CXCR4 Receptor: Role in HIV Infection

Answer 53

Chemokine co-receptors found on the surface of target cells (like CD4+ T cells and macrophages). HIV uses one or both of these (in addition to the CD4 receptor) to bind to and enter host cells. CCR5 antagonists are a class of ART.

Question 54

HIV Resistors (CCR5 Gene Mutation)

Answer 54

Individuals who have a specific genetic mutation (deletion) in the CCR5 gene (homozygous for CCR5-delta32 mutation) lack functional CCR5 co-receptors on their cells. This makes them highly resistant to infection by HIV strains that use CCR5 for entry (R5-tropic viruses).

Question 55

Viral Load (HIV RNA Assay): Concept & Significance

Answer 55

Measures the amount of HIV genetic material (RNA copies) in a milliliter of blood. It is the most accurate measure of viral replication. Significance: Indicates disease severity, risk of progression to AIDS, and effectiveness of antiretroviral therapy. Goal of ART is an undetectable viral load.

Question 56

Seroconversion (HIV): Concept

Answer 56

The point in time when an individual infected with HIV develops detectable levels of antibodies against the virus in their bloodstream. Typically occurs 2 weeks to 6 months after infection. Before seroconversion, antibody tests may be negative despite active infection (window period).

Question 57

Window Period (HIV): Concept

Answer 57

The time between initial HIV infection and the development of detectable antibodies. During this period (typically 2 weeks to 6 months), an infected person can transmit the virus but may test negative on standard HIV antibody tests. HIV RNA or p24 antigen tests can detect infection earlier.

Question 58

p24 Antigen Test (HIV): Concept

Answer 58

A test that detects the p24 protein, a core structural protein of the HIV capsid. p24 antigen levels are high in the bloodstream shortly after infection (around day 14), before antibodies are detectable, and can decline after seroconversion. Often used in combination antibody/antigen screening tests for earlier diagnosis.

Question 59

Opportunistic Infection: General Definition

Answer 59

An infection caused by a pathogen (bacterium, virus, fungus, or parasite) that usually does not cause disease in a healthy individual but can cause disease in an individual with a weakened immune system (immunocompromised host), such as someone with AIDS or undergoing immunosuppressive therapy.

Question 60

Antiretroviral Therapy (ART): General Definition

Answer 60

A treatment regimen for HIV infection consisting of a combination of different antiretroviral drugs that suppress HIV replication by targeting various stages of the viral life cycle. ART does not cure HIV but can control the virus, preserve immune function, and prevent progression to AIDS.