AGGLUTINATION & COMPLEMENT Flashcards
What is agglutination?
A serologic reaction where particulate antigens form clumps in response to antibodies.
What are the types of agglutination?
Direct agglutination, Indirect agglutination, Passive agglutination, Reverse passive agglutination, Agglutination inhibition.
What is the principle of direct agglutination?
Uses a known antiserum to identify unknown antigens.
What is the principle of indirect agglutination?
Uses a known antigen to detect unknown antibodies in a sample.
What is passive agglutination?
An agglutination test where soluble antigens are coated onto particles such as latex beads.
What is reverse passive agglutination?
An agglutination test where antibodies are attached to particles instead of antigens.
What is agglutination inhibition?
A modified agglutination reaction used for detecting small amounts of antigens.
What are common clinical applications of agglutination tests?
Diagnosis of infections like typhoid, syphilis, and streptococcal diseases.
What is the Widal test used for?
A serologic test for the diagnosis of enteric (typhoid) fever.
What principle does the Widal test use?
Direct agglutination of Salmonella ‘O’ and ‘H’ antigens with patient serum.
What specimen is used for the Widal test?
Blood, urine, and stool samples.
What is the Weil-Felix test used for?
Diagnosis of rickettsial infections using Proteus OX antigen cross-reactivity.
What is the principle of the Weil-Felix test?
Direct agglutination using Proteus species antigens.
What are the bacterial strains used in the Weil-Felix test?
Proteus OX19, OX2, and OXK.
What is the Brucella agglutination test used for?
Diagnosis of brucellosis, a zoonotic bacterial infection.
What specimen is used for the Brucella test?
Serum.
What is complement fixation?
A classic method of detecting antigen-specific antibodies.
What is the role of complement in immunity?
Plays a key role in immunity by aiding in pathogen destruction.
What are the two components of complement fixation?
Patient serum exposed to antigen and complement (1st step), then an indicator system (2nd step) using sheep RBCs.
What indicates a positive complement fixation test?
Absence of red cell lysis, indicating complement fixation.
What indicates a negative complement fixation test?
Presence of hemolysis, meaning complement was not fixed.
What are the three pathways of complement activation?
Classical, Alternative, and Lectin pathways.
What is the classical pathway of complement activation?
Activated by antigen-antibody complexes.
What is the alternative pathway of complement activation?
Triggered by microbial surfaces without antibody involvement.
What is the lectin pathway of complement activation?
Activated by mannose-binding lectin binding to pathogen surfaces.
What is the function of C3 in the complement system?
Central protein of the complement cascade, involved in opsonization and inflammation.
What is the function of C5 in the complement system?
Triggers membrane attack complex (MAC) formation.
What is a complement deficiency?
A condition where a part of the complement system is missing or dysfunctional.
What diseases are associated with complement deficiencies?
Lupus, recurrent infections, and hereditary angioedema.
What is the CH50 assay used for?
Measures total classical complement activity.
What is the AH50 assay used for?
Measures total alternative complement activity.
What is the principle of the radial immunodiffusion test?
A method for quantifying complement proteins using antigen-antibody precipitation.
What is the function of C1 in the complement cascade?
Initiates the classical pathway by binding to antigen-antibody complexes.
What is the function of C9 in the complement cascade?
Forms the pore of the membrane attack complex (MAC).
What are the regulatory proteins of the complement system?
C1 inhibitor, Factor H, Factor I, CD59, and DAF.
What is the membrane attack complex (MAC)?
A complex of C5b-C9 that forms pores in target cell membranes.
What is complement-mediated cytolysis?
Lysis of pathogens and infected cells via the MAC.
What is the importance of complement fixation in serology?
Used in detecting infections, immune disorders, and complement deficiencies.
What is an immune complex disease?
A disorder where immune complexes activate excessive complement leading to inflammation.
What role does complement play in autoimmune diseases?
Leads to increased tissue damage and inflammation in autoimmune diseases.
How is complement involved in bacterial infections?
Helps recognize and eliminate bacterial pathogens.
What role does complement play in viral infections?
Enhances viral clearance through opsonization and lysis of infected cells.
How does complement contribute to inflammation?
Triggers release of inflammatory mediators like C3a and C5a.
What are the inhibitors of the complement system?
C1 inhibitor, Factor H, CD59, and DAF regulate complement activation.
What are complement receptors and their functions?
Recognize complement-coated microbes and facilitate immune responses.
What lab tests measure complement activity?
CH50, AH50, C3, C4, and functional assays.
What are the clinical signs of complement overactivation?
Excessive inflammation, tissue damage, and autoimmune flare-ups.
What happens when complement is deficient?
Increased susceptibility to infections and immune complex diseases.
What are the therapeutic uses of complement inhibitors?
Used in diseases like paroxysmal nocturnal hemoglobinuria (PNH).
What are the biomarkers of complement activation?
C3a, C5a, C5b-9 complex levels in blood.
