AGGLUTINATION & COMPLEMENT

Question 1

What is agglutination?

Answer 1

A serologic reaction where particulate antigens form clumps in response to antibodies.

Question 2

What are the types of agglutination?

Answer 2

Direct agglutination, Indirect agglutination, Passive agglutination, Reverse passive agglutination, Agglutination inhibition.

Question 3

What is the principle of direct agglutination?

Answer 3

Uses a known antiserum to identify unknown antigens.

Question 4

What is the principle of indirect agglutination?

Answer 4

Uses a known antigen to detect unknown antibodies in a sample.

Question 5

What is passive agglutination?

Answer 5

An agglutination test where soluble antigens are coated onto particles such as latex beads.

Question 6

What is reverse passive agglutination?

Answer 6

An agglutination test where antibodies are attached to particles instead of antigens.

Question 7

What is agglutination inhibition?

Answer 7

A modified agglutination reaction used for detecting small amounts of antigens.

Question 8

What are common clinical applications of agglutination tests?

Answer 8

Diagnosis of infections like typhoid, syphilis, and streptococcal diseases.

Question 9

What is the Widal test used for?

Answer 9

A serologic test for the diagnosis of enteric (typhoid) fever.

Question 10

What principle does the Widal test use?

Answer 10

Direct agglutination of Salmonella ‘O’ and ‘H’ antigens with patient serum.

Question 11

What specimen is used for the Widal test?

Answer 11

Blood, urine, and stool samples.

Question 12

What is the Weil-Felix test used for?

Answer 12

Diagnosis of rickettsial infections using Proteus OX antigen cross-reactivity.

Question 13

What is the principle of the Weil-Felix test?

Answer 13

Direct agglutination using Proteus species antigens.

Question 14

What are the bacterial strains used in the Weil-Felix test?

Answer 14

Proteus OX19, OX2, and OXK.

Question 15

What is the Brucella agglutination test used for?

Answer 15

Diagnosis of brucellosis, a zoonotic bacterial infection.

Question 16

What specimen is used for the Brucella test?

Answer 16

Serum.

Question 17

What is complement fixation?

Answer 17

A classic method of detecting antigen-specific antibodies.

Question 18

What is the role of complement in immunity?

Answer 18

Plays a key role in immunity by aiding in pathogen destruction.

Question 19

What are the two components of complement fixation?

Answer 19

Patient serum exposed to antigen and complement (1st step), then an indicator system (2nd step) using sheep RBCs.

Question 20

What indicates a positive complement fixation test?

Answer 20

Absence of red cell lysis, indicating complement fixation.

Question 21

What indicates a negative complement fixation test?

Answer 21

Presence of hemolysis, meaning complement was not fixed.

Question 22

What are the three pathways of complement activation?

Answer 22

Classical, Alternative, and Lectin pathways.

Question 23

What is the classical pathway of complement activation?

Answer 23

Activated by antigen-antibody complexes.

Question 24

What is the alternative pathway of complement activation?

Answer 24

Triggered by microbial surfaces without antibody involvement.

Question 25

What is the lectin pathway of complement activation?

Answer 25

Activated by mannose-binding lectin binding to pathogen surfaces.

Question 26

What is the function of C3 in the complement system?

Answer 26

Central protein of the complement cascade, involved in opsonization and inflammation.

Question 27

What is the function of C5 in the complement system?

Answer 27

Triggers membrane attack complex (MAC) formation.

Question 28

What is a complement deficiency?

Answer 28

A condition where a part of the complement system is missing or dysfunctional.

Question 29

What diseases are associated with complement deficiencies?

Answer 29

Lupus, recurrent infections, and hereditary angioedema.

Question 30

What is the CH50 assay used for?

Answer 30

Measures total classical complement activity.

Question 31

What is the AH50 assay used for?

Answer 31

Measures total alternative complement activity.

Question 32

What is the principle of the radial immunodiffusion test?

Answer 32

A method for quantifying complement proteins using antigen-antibody precipitation.

Question 33

What is the function of C1 in the complement cascade?

Answer 33

Initiates the classical pathway by binding to antigen-antibody complexes.

Question 34

What is the function of C9 in the complement cascade?

Answer 34

Forms the pore of the membrane attack complex (MAC).

Question 35

What are the regulatory proteins of the complement system?

Answer 35

C1 inhibitor, Factor H, Factor I, CD59, and DAF.

Question 36

What is the membrane attack complex (MAC)?

Answer 36

A complex of C5b-C9 that forms pores in target cell membranes.

Question 37

What is complement-mediated cytolysis?

Answer 37

Lysis of pathogens and infected cells via the MAC.

Question 38

What is the importance of complement fixation in serology?

Answer 38

Used in detecting infections, immune disorders, and complement deficiencies.

Question 39

What is an immune complex disease?

Answer 39

A disorder where immune complexes activate excessive complement leading to inflammation.

Question 40

What role does complement play in autoimmune diseases?

Answer 40

Leads to increased tissue damage and inflammation in autoimmune diseases.

Question 41

How is complement involved in bacterial infections?

Answer 41

Helps recognize and eliminate bacterial pathogens.

Question 42

What role does complement play in viral infections?

Answer 42

Enhances viral clearance through opsonization and lysis of infected cells.

Question 43

How does complement contribute to inflammation?

Answer 43

Triggers release of inflammatory mediators like C3a and C5a.

Question 44

What are the inhibitors of the complement system?

Answer 44

C1 inhibitor, Factor H, CD59, and DAF regulate complement activation.

Question 45

What are complement receptors and their functions?

Answer 45

Recognize complement-coated microbes and facilitate immune responses.

Question 46

What lab tests measure complement activity?

Answer 46

CH50, AH50, C3, C4, and functional assays.

Question 47

What are the clinical signs of complement overactivation?

Answer 47

Excessive inflammation, tissue damage, and autoimmune flare-ups.

Question 48

What happens when complement is deficient?

Answer 48

Increased susceptibility to infections and immune complex diseases.

Question 49

What are the therapeutic uses of complement inhibitors?

Answer 49

Used in diseases like paroxysmal nocturnal hemoglobinuria (PNH).

Question 50

What are the biomarkers of complement activation?

Answer 50

C3a, C5a, C5b-9 complex levels in blood.