Rest of Chapter 16

Comprehensive vocabulary flashcards covering cell-mediated immunity (T-cell subsets, NK cells), antigens and antibodies (classes, structure, serological reactions), immunodeficiencies, hypersensitivities, tissue grafts, vaccine platforms, and herd immunity.

Cell-Mediated Immunity (T-Cells)

The branch of adaptive immunity mediated by T-lymphocytes, which develop receptors (TCRs) and mature in the thymus.

Helper T-Cells ($T_H$)

T-lymphocytes bearing CD4 receptors that coordinate immune responses; CD4+ T-cell counts are monitored on clinical reports for HIV.

$T_H1$ Cells

A subset of helper T-cells that interact with cytotoxic T-cells ($T_c$) and macrophages ($\text{M}\varnothing$) to destroy intracellular pathogens and fight viruses.

$T_H2$ Cells

A subset of helper T-cells that interact with B-cells, help fight parasitic infections, and are involved in allergic responses.

Cytotoxic T-Cells ($T_c$)

T-lymphocytes bearing CD8 receptors that interact with presented antigens to destroy infected or abnormal cells.

Gamma-Delta ($\gamma\delta$) T-Cells

Rapid-response T-cells that defend body tissues against infections and abnormal cells by recognizing pathogen-associated molecular patterns (PAMPs).

Pathogen-Associated Molecular Patterns (PAMPs)

Conserved molecular structures commonly found on pathogens that are recognized by immune cells, such as gamma-delta ($\gamma\delta$) T-cells.

Natural Killer (NK) Cells

Innate immune lymphocytes that kill virus-infected cells without requiring prior exposure to the pathogen.

Antibody-Dependent Cellular Cytotoxicity (ADCC)

A cell-mediated immune mechanism where effector cells recognize antibody-coated target cells and destroy them.

Antigen (Ag)

Also called an immunogen; a molecule (usually a protein or large polysaccharide) of sufficient size that can induce an immune response.

Epitope (Antigenic Determinant)

The specific chemical portion of an antigen that an antibody or immune cell receptor directly recognizes and binds to.

Hapten

A small foreign molecule that cannot elicit an immune response on its own and only triggers one when attached to a larger carrier protein.

Superantigens

Virulence factors that non-specifically overstimulate T-cells, triggering a massive release of cytokines that leads to tissue damage, systemic inflammation, and potentially toxic shock.

Antibody (Ab)

Also called an immunoglobulin (Ig); a tetrameric protein produced by activated B-cells consisting of two heavy ($H$) chains, two light ($L$) chains, two identical antigen-binding sites, and one constant region.

Antibody Titer

A laboratory measurement of the quantity or detectable activity of specific antibodies in the blood, indicating a prior immune response to an antigen.

IgG

The most abundant antibody class with the longest half-life (approximately one month); it confers passive immunity to neonates because it can cross the placenta.

IgM

The first responder antibody class produced during a primary immune response.

IgA

The antibody class predominantly present in bodily secretions and mucus.

IgD

An antibody class that primarily acts as a receptor on B-cells to assist in their activation.

IgE

The least prevalent antibody class in circulation; involved in allergic responses and elevated during parasitic worm infections.

Complement Fixation

An immune reaction where an antigen-antibody complex triggers the sequential cascade of complement proteins.

Agglutination

The visible clumping of cells or particles caused by antibodies binding to surface antigens; commonly used in laboratory tests to determine blood type.

Opsonization

The process by which antibodies or complement proteins coat a pathogen, facilitating its recognition and engulfment by phagocytic cells.

Antigen Neutralization

The binding of antibodies to pathogens or their harmful products (such as toxins), preventing them from attaching to and damaging host cells.

Secondary (Anamnestic) Response

A rapid and robust immune response that occurs upon re-exposure to an antigen due to the persistence of memory B and T-cells.

Primary Immunodeficiency

A less common, congenital under-response of the immune system caused by genetic defects (e.g., severe combined immunodeficiency [SCID], which lacks functional B and T cells).

Secondary Immunodeficiency

An acquired under-response of the immune system resulting from external factors such as HIV (knocking out CD4+ helper T-cells), cancer chemotherapy, malnutrition (e.g., scurvy), or autoimmune diseases.

Hypersensitivity

An over-reaction of the immune system against foreign or self-antigens, encompassing allergy, autoimmunity, and alloimmunity.

Allergy

A hypersensitivity reaction occurring when the immune system mistakenly recognizes and attacks a harmless foreign substance as a threat.

Autoimmunity

A failure of self-tolerance in which the immune system targets and damages the body's own tissues.

Alloimmunity

An immune response mounted against foreign tissue or cells derived from another individual of the same species (e.g., allograft rejection).

Autograft

A tissue graft transplanted from one site to another on the same individual's body (e.g., using a saphenous vein for CABG, or autologous fat for a BBL).

Isograft

A tissue graft transplanted between genetically identical individuals, such as identical twins, which does not trigger an immune rejection.

Allograft

A graft transplanted from a genetically non-identical donor of the same species; triggers an immune response and typically requires immunosuppressants.

Xenograft

A graft harvested from a different species (e.g., animal-derived connective tissue) that triggers a strong immune response in the recipient.

Immunization

The administration of an immunogen to prime the immune system, conferring active immunity and enhanced defense against future pathogen encounters.

Whole Cell Vaccines

The traditional class of vaccines that uses entire microbial cells, most commonly attenuated (weakened) live pathogens.

Attenuated Vaccines

Vaccines formulated with live pathogens that have been weakened by culturing them under conditions that eliminate virulence.

Acellular / Subunit Vaccines

Vaccines that do not use whole pathogens, but instead contain purified bits and pieces such as proteins, peptides, or polysaccharides (e.g., the flu shot).

Toxoid Vaccines

Vaccines containing inactivated bacterial toxins that resemble the native toxin to prime the immune system against toxic products (e.g., the tetanus shot).

Recombinant Vaccines

Vaccines manufactured through molecular cloning techniques by cutting and pasting DNA or RNA to produce specific antigenic components (e.g., the hepatitis B vaccine).

mRNA Vaccines

Vaccines developed rapidly by synthesizing messenger RNA to instruct host cells to temporarily produce and display a specific pathogen antigen.

Vector Vaccines

Vaccines that utilize a harmless, modified delivery virus (such as an adenoviral vector) to transport genetic instructions for an antigen into host cells.

Adjuvant

A chemical substance added to a vaccine formulation to stimulate a stronger and more effective immune response to the antigen.

Herd Immunity

The indirect protection of susceptible, unvaccinated individuals within a population that occurs when a high proportion of people are immune, limiting pathogen spread.