Immunology & Serology Testing Methods Flashcards

Vocabulary practice flashcards created from the lecture notes covering serial dilutions, serological principles, agglutination and precipitation methods, DAT/IAT testing, nephelometry, immunodiffusion, and serum protein electrophoresis.

Dilution

A relative expression of concentration representing the amount of substance in a solution relative to total volume, expressed as a ratio of starting volume over final total volume.

Dilution Factor

The reciprocal multiplier of a dilution used to correct the concentration result obtained from a diluted sample back to its original undiluted value.

Serial Dilution

A stepwise succession of dilutions where each tube has the same tube dilution factor, progressively increasing the overall dilution ratio.

Serology

The study of serum components in the blood, particularly used to detect and quantify antibodies.

Antibody Titer

The reciprocal of the highest dilution in a serial dilution series that still demonstrates visible reactivity (endpoint).

Acute Titer

An antibody titer measured during the acute phase of an illness, defined as the time when the disease is first suspected or diagnosed.

Convalescent Titer

An antibody titer measured during the recovery period, typically a few weeks after the initial infection.

Fourfold Rise in Titer

A quadrupling of antibody titer between acute and convalescent phase specimens, used as diagnostic evidence of a specific clinical infection.

Seropositive

The state of having demonstrable antibodies to a specific illness in serum.

Seronegative

The state of lacking demonstrable antibodies to a specific illness in serum.

Seroconversion

The immunological process of transitioning from being seronegative to seropositive as detectable antibodies develop.

Precipitation

A reaction in which a soluble antigen combines with a soluble antibody to form an insoluble precipitate.

Agglutination

The process in which particulate or cellular antigens aggregate with specific antibodies to form larger, visible complexes.

Flocculation

A specific reaction intermediate between precipitation and agglutination where soluble antigen and antibody form flake-like structures confined within a defined area (e.g., RPR and VDRL testing).

Sensitization

The first, reversible stage of agglutination involving the physical attachment of individual antibody molecules to target antigens.

Lattice Formation

The second stage of agglutination where sensitized particles and antibodies crosslink to form visible clumps.

Optimum Reaction pH for Agglutination

The ideal pH range for antigen-antibody reactions to take place, defined as $6.5\text{ to }7.5$.

Steric Hindrance

Different antibodies/proteins with similar affinities competing for nearby epitopes. Prevents simultaneous binding and can cause false negatives

Zeta Potential

The net electrical charge surrounding particles (such as red blood cells) that causes repulsion between cells and affects antibody uptake and crosslinking.

Low Ionic Strength Solution (LISS)

An enhancement reagent used in blood banking to lower salt concentration and reduce the zeta potential, facilitating antibody crosslinking.

Prozone Phenomenon

A false-negative agglutination or precipitation reaction caused by antibody excess relative to antigen concentration.

Post Zone

A false-negative agglutination or precipitation reaction caused by antigen excess relative to antibody concentration.

Zone of Equivalence

The optimal ratio of multivalent antigen and antibody sites that yields maximum lattice formation, precipitation, or agglutination.

Rouleaux

A pseudoagglutination phenomenon where red cells stack like coins due to excess plasma proteins (such as high IgG in multiple myeloma or IgM in Waldenström's).

Saline Replacement

A procedure used to differentiate rouleaux from true agglutination by replacing patient plasma with saline; rouleaux disperses, whereas true agglutination remains.

Incomplete Antibody

An antibody, such as IgG, that binds to antigen but cannot directly cause visible agglutination of red blood cells without enhancement methods.

Direct Antiglobulin Test (DAT / Direct Coombs)

A test that detects antibodies or complement proteins bound to red blood cells in vivo (inside the human body).

Indirect Antiglobulin Test (IAT / Indirect Coombs)

A test that detects free, unattached red blood cell antibodies in patient plasma or serum in vitro.

Nephelometry

A quantitative assay technique that measures the concentration of antigen-antibody complexes based on the intensity of light scattered by immune complexes in solution.

Radial Immunodiffusion (RID / Auden Test)

A quantitative single immunodiffusion assay where antibody is embedded in agar gel and antigen diffuses outward to form a precipitate ring whose diameter is proportional to antigen concentration.

Double Immunodiffusion (Ouchterlony)

A qualitative assay where both antigen and multispecific antibody diffuse through agar gel to assess structural relationships (identity, nonidentity, partial identity) over $18\text{ to }48$\,hours.

Serum Protein Electrophoresis (SPEP)

A technique separating plasma proteins into five distinct fractions (albumin, alpha-1, alpha-2, beta, gamma) based on charged particle migration in an electrical field.

Monoclonal Gammopathy

A primary plasma cell disorder where a single clone of plasma cells produces an excess of a single immunoglobulin class, forming a narrow M spike on SPEP.

Polyclonal Gammopathy

A secondary disorder (often due to liver or kidney disease) where multiple plasma cell clones produce increased levels of two or more immunoglobulin classes, appearing as a broad elevated band on SPEP.

Immunofixation Electrophoresis (IFE)

Combines protein electrophoresis with immunoprecipitation using monospecific antisera identifying specific heavy chains (IgM, IgG, IgA) and light chains (Kappa, lambda)

Monoclonal Gammopathy of Undetermined Significance (MGUS)

A condition characterized by a monoclonal protein spike that requires regular serum and urine monitoring due to potential risk of progression to multiple myeloma.