BASIC SEROLOGICAL PRINCIPLES AND CONCEPTS Flashcards
▪ The science that deals with the
identification, characterization, and
measurement of antigens, antibodies,
and other immunological substances
using body fluids, most commonly
serum, for the diagnosis, treatment, and
monitoring of infection.
SEROLOGY
An____\ is a process in which antibodies bind to specific antigens.
This is a key mechanism in the adaptive immune response, as it allows the immune system to target and neutralize specific pathogens and
toxins
antigen-antibody reaction
FACTORS INFLUENCING ANTIGEN-ANTIBODY REACTIONS
Affinity
Avidity
pH
Time
Centrifugation
Temperature
Physical form
Concentration
_______signifies the strength of the bond between a single antibody-binding site and a single epitope on an antigen.
A strong______ suggests a good fit between the two, increasing the
likelihood of a lasting interaction.
Affinity
is determined by the three-dimensional fit and molecular attractions between one antigenic determinant and one antibody-binding site.
Affinity
• Reflects the overall strength of the bond when multiple binding sites on an antibody attach to multiple epitopes on an antigen.
AVIDITY
is the sum of the forces binding multivalent antigens to multivalent antibodies. In a comparison between IgG and IgM, IgM has the most potential binding sites for antigen and thus the higher avidity.
Avidity
The ability of an antibody to bind to an antigen that is structurally similar to the original antigen that induced its production.
• This is possible because the binding site of an antibody, while specific to the original antigen, may partially fit and bind to similar regions
(epitopes) on different antigens.
CROSS-REACTIVITY
______of the surrounding environment affects the charges on both antigens and antibodies.
• Maintaining a near-physiological_____ IS essential for optimal antigen-antibody interactions
pH
pH
(6.8-7.0)
is a crucial factor as it allows for the gradual formation of the antigen-antibody lattice, the network of interconnected molecules
Time
• The longer the incubation period…
the greater the chance for antibodies to collide and bind with antigens, leading to a more pronounced reaction.
• acts as a catalyst, speeding up the process.
• It forces antigens and antibodies
closer together, increasing the frequency of collisions and promoting faster lattice formation
Centrifugation
T or F
TEMPERATURE
• Different antibody isotypes
have different optimal temperature ranges.
True
- often involved in the initial immune response, function best at lower
temperatures..
IgM antibodies
(4°C to 27°C)
• antibodies associated with
encounters, prefer subsequent warmer
temperatures
IgG
(30°C to 37°C).
PHYSICAL FORM
•______ lead to precipitation reactions, forming insoluble complexes
•______, such as cells, result in agglutination, clumping together in the presence of antibodies
Soluble antigens
Particulate antigens
The relative amounts of antigens and antibodies, is key for a visible reaction.
CONCENTRATION
CONCENTRATION
The relative amounts of antigens and antibodies, is key for a visible reaction.
The_______, where the concentrations are optimal for maximum binding and lattice formation, results in the most
pronounced precipitation.
zone of equivalence
CONCENTRATION
The relative amounts of antigens and antibodies, is key for a visible reaction.
An excess of either antigen or antibody can lead to the_______, respectively, hindering the visibility of the reaction (false negative).
prozone or postzone phenomenon
Zone of equivalence:
This is the point where antigen and antibody concentrations are perfectly balanced, allowing for maximum binding. This leads to the formation of large lattice structures, which results in a visible precipitate.
Prozone phenomenon:
When there is an excess of antibodies relative to antigens, the antibodies saturate all binding sites on the antigens.
This prevents the formation of large lattices and results in a false negative reaction, where no visible precipitation is observed.
Postzone phenomenon:
When there is an excess of antigens compared to antibodies, not enough antibodies are available to form large complexes.
This also prevents visible precipitation, leading to a false negative result.
: detects presence or absence of Ab/Ag
: - determine concentration of Ab/Ag
• Qualitative test
• Quantitative test
• Concentration of an antibody expressed as the highest dilution of a serum that produces a positive result.
reciprocal of the dilution of positive result
Titer
: time where antibodies start to appear
• the development of detectable specific antibodies in serum
: time where antibodies start to disappear
• opposite of seroconversion.
• Seroconversion
• Seroreversion
: refers to the smallest amount of a target substance (analyte) that a test can reliably measure.
• Analytical sensitivity
: refers to the smallest amount of a target substance (analyte) that a test can reliably measure.
• Analytical sensitivity
: Refers to the ability of a test to correctly identify individuals with a specific disease or condition.
Clinical sensitivity
: describes a test’s ability to differentiate the target analyte from other substances present in the sample.
Analytical specificity
Refers to the ability of a test to correctly
identify individuals without the disease or condition.
Clinical specificity:
refers to the ability of a test to correctly identify individuals who have a specific disease or condition. A test with high sensitivity will detect most true cases, minimizing the chance of false negatives (missing cases of the disease).
refers to the ability of a test to correctly identify individuals who do not have the disease or condition. A test with high specificity minimizes false positives, meaning it correctly identifies healthy individuals without mistakenly labeling them as diseased.
Clinical sensitivity
Clinical specificity
PRIMARY IMMUNE RESPONSE
Antibody isotype
• Predominantly gM antibodies produced initially, followed by a gradual switch to IgG (and other isotypes) in the later stages.
Primary IR
DURATION
• Relatively short-lived, with antibody levels declining gradually as the antigen is cleared and effector lymphocytes undergo apoptosis.
Primary IR
MEMORY
• Results in the generation of memory lymphocytes (both T and B cells) that provide long-term immunity against the specific antigen. These memory cells are responsible for the rapid and enhanced response upon subsequent encounters with the same antigen.
Primary IR
MEMORY
• Results in the generation of memory lymphocytes (both T and B cells) that provide long-term immunity against the specific antigen. These memory cells are responsible for the rapid and enhanced response upon subsequent encounters with the same antigen.
Secondary IR
Antibody isotype
SECONDARY IMMUNE RESPONSE
• Predominantly IgG antibodies produced. This reflects the isotype switching that occurred during the primary response and the persistence of IgG-secreting memory B cells.
Secondary IR
Duration
Longer-lasting, with antibody levels remaining elevated for an extended period due to the persistence of memory lymphocytes.
Secondary IR
Memory
• Characterized by the reactivation and expansion of memory lymphocytes, further amplitying the immune response
and strengthening immunological memory.
• The initial immune response to a new antigen, characterized by the generation of; naive lymphocytes that differentiate into effector and memory cells.
Primary IR
• A subsequent encounter with the same antigen,! triggering a faster and more robust immune response due to the activation of memory! lymphocytes.
SECONDARY IMMUNE RESPONSE
Primary IR
Lag phase
• Longer (typically several days to weeks) as naive lymphocytes require time to recognize, activate, and differentiate into effector cells.
Primary IR
ANTIBODY TITER
• Lower peak levels attained due to the limited number of antigen-specific lymphocytes initially present.
Secondary IR
Lag phase
Significantly shorter due to the presence of preexisting memory lymphocytes
with a lower activation threshold and faster response time.
Secondary IR
Antibody titer
• Significantly higher peak levels achieved due to the rapid proliferation and differentiation of memory lymphocytes, resulting in a more robust! antibody response.
