BASIC SEROLOGICAL PRINCIPLES AND CONCEPTS

Question 1

▪ 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.

Answer 1

SEROLOGY

Question 2

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

Answer 2

antigen-antibody reaction

Question 3

FACTORS INFLUENCING ANTIGEN-ANTIBODY REACTIONS

Answer 3

Affinity
Avidity
pH
Time
Centrifugation
Temperature
Physical form
Concentration

Question 4

_______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.

Answer 4

Affinity

Question 5

is determined by the three-dimensional fit and molecular attractions between one antigenic determinant and one antibody-binding site.

Answer 5

Affinity

Question 6

• Reflects the overall strength of the bond when multiple binding sites on an antibody attach to multiple epitopes on an antigen.

Answer 6

AVIDITY

Question 7

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.

Answer 7

Avidity

Question 8

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.

Answer 8

CROSS-REACTIVITY

Question 9

______of the surrounding environment affects the charges on both antigens and antibodies.

• Maintaining a near-physiological_____ IS essential for optimal antigen-antibody interactions

Answer 9

pH

pH
(6.8-7.0)

Question 10

is a crucial factor as it allows for the gradual formation of the antigen-antibody lattice, the network of interconnected molecules

Answer 10

Time

Question 11

• The longer the incubation period…

Answer 11

the greater the chance for antibodies to collide and bind with antigens, leading to a more pronounced reaction.

Question 12

• 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

Answer 12

Centrifugation

Question 13

T or F

TEMPERATURE
• Different antibody isotypes
have different optimal temperature ranges.

Answer 13

True

Question 14

• often involved in the initial immune response, function best at lower
  temperatures..

Answer 14

IgM antibodies

(4°C to 27°C)

Question 15

• antibodies associated with
encounters, prefer subsequent warmer
temperatures

Answer 15

IgG

(30°C to 37°C).

Question 16

PHYSICAL FORM
•______ lead to precipitation reactions, forming insoluble complexes

•______, such as cells, result in agglutination, clumping together in the presence of antibodies

Answer 16

Soluble antigens

Particulate antigens

Question 17

The relative amounts of antigens and antibodies, is key for a visible reaction.

Answer 17

CONCENTRATION

Question 18

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.

Answer 18

zone of equivalence

Question 19

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).

Answer 19

prozone or postzone phenomenon

Question 20

Zone of equivalence:

Answer 20

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.

Question 21

Prozone phenomenon:

Answer 21

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.

Question 22

Postzone phenomenon:

Answer 22

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.

Question 23

: detects presence or absence of Ab/Ag
: - determine concentration of Ab/Ag

Answer 23

• Qualitative test

• Quantitative test

Question 24

• Concentration of an antibody expressed as the highest dilution of a serum that produces a positive result.
reciprocal of the dilution of positive result

Answer 24

Titer

Question 25

: time where antibodies start to appear
• the development of detectable specific antibodies in serum

: time where antibodies start to disappear
• opposite of seroconversion.

Answer 25

• Seroconversion

• Seroreversion

Question 26

: refers to the smallest amount of a target substance (analyte) that a test can reliably measure.

Answer 26

• Analytical sensitivity

Question 27

: refers to the smallest amount of a target substance (analyte) that a test can reliably measure.

Answer 27

• Analytical sensitivity

Question 28

: Refers to the ability of a test to correctly identify individuals with a specific disease or condition.

Answer 28

Clinical sensitivity

Question 29

: describes a test’s ability to differentiate the target analyte from other substances present in the sample.

Answer 29

Analytical specificity

Question 30

Refers to the ability of a test to correctly
identify individuals without the disease or condition.

Answer 30

Clinical specificity:

Question 31

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.

Answer 31

Clinical sensitivity

Clinical specificity

Question 32

PRIMARY IMMUNE RESPONSE

Antibody isotype

Answer 32

• Predominantly gM antibodies produced initially, followed by a gradual switch to IgG (and other isotypes) in the later stages.

Question 33

Primary IR

DURATION

Answer 33

• Relatively short-lived, with antibody levels declining gradually as the antigen is cleared and effector lymphocytes undergo apoptosis.

Question 34

Primary IR

MEMORY

Answer 34

• 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.

Question 35

Primary IR

MEMORY

Answer 35

• 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.

Question 36

Secondary IR

Antibody isotype

Answer 36

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.

Question 37

Secondary IR

Duration

Answer 37

Longer-lasting, with antibody levels remaining elevated for an extended period due to the persistence of memory lymphocytes.

Question 38

Secondary IR

Memory

Answer 38

• Characterized by the reactivation and expansion of memory lymphocytes, further amplitying the immune response
and strengthening immunological memory.

Question 39

• The initial immune response to a new antigen, characterized by the generation of; naive lymphocytes that differentiate into effector and memory cells.

Answer 39

Primary IR

Question 40

• A subsequent encounter with the same antigen,! triggering a faster and more robust immune response due to the activation of memory! lymphocytes.

Answer 40

SECONDARY IMMUNE RESPONSE

Question 41

Primary IR

Lag phase

Answer 41

• Longer (typically several days to weeks) as naive lymphocytes require time to recognize, activate, and differentiate into effector cells.

Question 42

Primary IR

ANTIBODY TITER

Answer 42

• Lower peak levels attained due to the limited number of antigen-specific lymphocytes initially present.

Question 43

Secondary IR

Lag phase

Answer 43

Significantly shorter due to the presence of preexisting memory lymphocytes
with a lower activation threshold and faster response time.

Question 44

Secondary IR

Antibody titer

Answer 44

• Significantly higher peak levels achieved due to the rapid proliferation and differentiation of memory lymphocytes, resulting in a more robust! antibody response.