Laboratory Science Immunology and Serology 2

Question 1

What does a positive monospot (heterophile antibody) test indicate?

Accepted Answer

Infectious mononucleosis (Epstein-Barr virus)

Answer

The monospot test detects heterophile antibodies produced during EBV-caused infectious mononucleosis; these IgM antibodies agglutinate horse or sheep RBCs in the rapid latex test.

Question 2

Which CD marker is used to identify T helper lymphocytes, and its count monitors HIV/AIDS progression?

Accepted Answer

CD4

Answer

CD4+ T helper cells are the primary target of HIV; CD4 count monitors immune status, with counts <200 cells/µL defining AIDS and increasing risk of opportunistic infections.

Question 3

What is the ELISA test principle used in serology?

Accepted Answer

Enzyme-linked antibody detecting antigen-antibody reactions via color change

Answer

ELISA uses enzyme-conjugated antibodies; when the target antigen or antibody is present, substrate is cleaved by the enzyme producing a measurable color change proportional to the concentration.

Question 4

Which complement pathway is activated by antigen-antibody complexes (IgG or IgM)?

Accepted Answer

Classical pathway

Answer

The classical complement pathway is initiated by C1q binding to Fc regions of antigen-bound IgG or IgM, triggering the C1-C2-C4 cascade and ultimately forming the membrane attack complex.

Question 5

A Western blot test in HIV diagnosis detects antibodies to which viral proteins?

Accepted Answer

Structural proteins: gag (p24, p17), pol (p31, p51, p66), and env (gp41, gp120/160)

Answer

HIV Western blot detects antibodies to multiple viral proteins; CDC criteria for positivity require bands for at least two of p24, gp41, and gp120/160 to confirm HIV infection.

Laboratory Science Practice Test

Laboratory Science Practice Test

Laboratory Science Immunology and Serology 2