Immunology and Serology Review

Vocabulary flashcards covering key terms, definitions, and diagnostic image figures in Immunology and Serology.

Immunology

The study of the reaction of a host when foreign substances are introduced into the body, including all aspects of body defenses against infections, tumors, allergy, and hypersensitivity.

Variolation

A historical method of immunoprophylaxis involving the deliberate exposure of a non-immune individual to material from smallpox lesions or scabs to induce protection against smallpox.

Attenuation

The process of weakening bacteria or viruses through modifying conditions such as chemical treatment, temperature extremes, aging, or repeated in vitro cell culture passage, rendering them non-pathogenic while retaining immunogenicity.

Immunoprophylaxis

The prevention of infectious disease through active or passive immunization.

Cross-immunity

The phenomenon in which exposure to one infectious or immunogenic agent generates immune protection against another related agent.

Innate Immunity

The individual's natural ability to resist infection through non-adaptive, non-specific mechanisms present at birth that lack immunological memory and do not require prior exposure.

Adaptive Immunity

A specific immune response characterized by recognition of specific individual pathogen epitopes, immunological memory of prior exposure, and heightened response upon repeated contact.

Competitive Exclusion

The phenomenon in which normal microbial flora occupy anatomical sites and prevent pathogenic organisms from establishing infection.

Acute-Phase Reactants

Normal serum proteins produced primarily by hepatocytes within $12$ to $24\,\text{hours}$ of infection, injury, or trauma that increase rapidly by at least $25\%$.

C-Reactive Protein (CRP)

A major acute-phase reactant and trace serum protein that binds to phosphocholine on microbial membranes and promotes opsonization, agglutination, precipitation, and classical complement activation.

Opsonization

The coating of foreign particles or microorganisms with serum proteins such as $IgG$, $C3b$, or CRP to enhance their recognition and ingestion by phagocytes.

Chemotaxis

The directed migration of phagocytic cells toward a chemical stimulus or gradient generated by chemotaxins such as complement fragments or bacterial products.

Diapedesis

The process by which white blood cells squeeze between endothelial cell borders of blood vessels to migrate from blood into surrounding tissue (also called transmigration).

Respiratory Burst

An oxygen-dependent metabolic process in phagocytes leading to the production of reactive oxygen species such as $H_2O_2$, superoxide anions, hydroxyl radicals, and hypochlorite ions to kill ingested microbes.

Pathogen-Associated Molecular Patterns (PAMPs)

Conserved, recurring molecular motifs expressed by large groups of microorganisms that are recognized by the innate immune system.

Pattern Recognition Receptors (PRRs)

Receptors expressed by cells of the innate immune system that specifically bind pathogen-associated molecular patterns (PAMPs).

Toll-Like Receptors (TLRs)

A class of transmembrane pattern recognition receptors present on cell surfaces or endosomes that recognize specific microbial PAMPs.

Active Immunity

Long-lasting immunity acquired when the host's own immune system is challenged by an antigen to produce specific antibodies and memory cells.

Passive Immunity

Temporary immune protection provided by the direct transfer or administration of preformed antibodies without activation of the host's immune response.

Epitope

The specific determinant site on an immunogen or antigen that is recognized and bound by an antibody or T-cell receptor.

Paratope

The specific antigen-binding site on an antibody molecule that interacts with an antigenic epitope.

Hapten

A small, non-immunogenic substance that cannot stimulate an antibody response on its own, but can react with specific antibodies once formed and become immunogenic when conjugated to a carrier protein.

Adjuvant

A compound administered alongside an immunogen to enhance, accelerate, or prolong the immune response.

Major Histocompatibility Complex (MHC)

A group of genes located on human chromosome $6$ encoding cell-surface molecules essential for antigen presentation to T cells and discrimination of self from non-self.

Isotype

Heavy chain constant region structures unique to each immunoglobulin class ($IgG$, $IgM$, $IgA$, $IgD$, $IgE$) present in all healthy individuals of a species.

Allotype

Genetically determined amino acid variations in the constant regions of immunoglobulins that differ among individual members of the same species.

Idiotype

Structural variation in the variable regions ($V_H$ and $V_L$) of an antibody molecule that forms its unique antigen-binding site.

Hybridoma Technology

A production method for monoclonal antibodies involving the fusion of antibody-producing B cells with immortal myeloma cells using polyethylene glycol ($PEG$).

Complement System

A humoral cascade of approximately $14$ distinct serum proteins that function in innate and adaptive immunity to promote opsonization, inflammation, chemotaxis, and cell lysis.

Anaphylatoxin

Small complement peptides ($C3a$, $C4a$, $C5a$) that trigger smooth muscle contraction, increased vascular permeability, and histamine release from mast cells and basophils.

Cytokine

Low-molecular-weight chemical protein messengers that mediate inter-cellular communication and regulate immune responses.

Pleiotropy

A property of cytokines wherein a single cytokine can produce multiple distinct biological actions on different target cell types.

Cytokine Storm

A severe, uncontrolled hyper-production of inflammatory cytokines that can result in systemic tissue damage, vascular collapse, shock, and organ failure.

Hypersensitivity

An exaggerated or inappropriate immune response to a foreign or self-antigen that results in host tissue injury or disease.

Atopy

A genetically predisposed tendency to develop classic allergic responses ($IgE$-mediated Type I hypersensitivity) to naturally occurring environmental allergens.

Autoimmunity

A pathological condition characterized by the breakdown of self-tolerance, leading to immune responses directed against the host's own tissues.

Rheumatoid Factor (RF)

An autoantibody, most commonly of the $IgM$ class, directed against the Fc region of self-$IgG$.

Heterophile Antibodies

Antibodies produced in response to one antigen that cross-react with structurally related antigens derived from completely different, unrelated species.

Affinity

The initial attractive force between a single Fab binding site on an antibody and a single epitope on an antigen.

Avidity

The overall functional strength of binding between a multivalent antibody and a multivalent antigen.

Zone of Equivalence

The optimal ratio of antigen to antibody concentration in a precipitation reaction where extensive lattice formation and maximal precipitate occur.

Prozone Phenomenon

An imbalance in an Ag-Ab reaction caused by antibody excess, preventing cross-linking and leading to false-negative precipitation or agglutination results.

Postzone Phenomenon

An imbalance in an Ag-Ab reaction caused by antigen excess, resulting in small unlinked complexes and false-negative test results.

Turbidimetry

A technique measuring the reduction in light transmission through a solution caused by scattered light from immune complexes.

Nephelometry

A method measuring light scattered at a specific angle (typically $10^\circ$ to $90^\circ$) from an incident beam passing through a suspension of immune complexes.

Agglutination

The aggregation or clumping of particulate antigens (such as RBCs or latex beads) when bound by specific antibodies.

Serological Identity (Ouchterlony)

A double immunodiffusion pattern characterized by a smooth continuous precipitin arc, demonstrating that two tested antigens contain identical epitopes.

Non-Identity (Ouchterlony)

A double immunodiffusion pattern characterized by two distinct precipitin lines that cross completely, demonstrating that the two antigens share no common epitopes.

Partial Identity (Ouchterlony)

A double immunodiffusion pattern featuring a spur pointing toward the well with the simpler antigen, indicating that the antigens share a common epitope but one possesses additional unique determinants.

Rocket Immunoelectrophoresis

A quantitative technique combining radial immunodiffusion with electrophoresis, where the height of the rocket-shaped precipitin peak is directly proportional to antigen concentration.

Fluorescent Antinuclear Antibody (FANA) Patterns

Diagnostic nuclear staining patterns (homogeneous, speckled, peripheral, nucleolar) observed under fluorescence microscopy using HEp-2 cells to detect anti-nuclear autoantibodies.

HIV Virion Structure

The structural layout of the Human Immunodeficiency Virus, comprising an outer envelope with $gp120$ and $gp41$ glycoproteins, an inner $p17$ matrix, a $p24$ capsid, and core RNA with reverse transcriptase.