MLPAO MLPAO Immunology and Serology 2

Question 1

In a Western blot (immunoblot), what is the purpose of the electrophoresis step?

Accepted Answer

To separate proteins by molecular weight before antibody probing

Answer

To denature all proteins so antibodies cannot bind

Answer

To amplify specific DNA sequences

Answer

To concentrate antigens onto nitrocellulose

Question 2

Which serological test is based on the principle that patient antibodies, if present, will prevent complement-mediated lysis of sensitized red blood cells?

Accepted Answer

Complement fixation test

Answer

Latex agglutination

Answer

Indirect immunofluorescence

Answer

Immunodiffusion

Question 3

ANA (antinuclear antibody) testing by indirect immunofluorescence using HEp-2 cells: a homogeneous staining pattern is most commonly associated with antibodies to:

Accepted Answer

Double-stranded DNA or histones

Answer

Centromere proteins

Answer

Ribosomes

Answer

Sm antigen

Question 4

The MHC class II molecules present antigen to which subset of T lymphocytes?

Accepted Answer

CD4+ helper T cells

Answer

CD8+ cytotoxic T cells

Answer

Natural killer cells

Answer

Regulatory T cells only

Question 5

Which serological marker is the first to appear after hepatitis B infection and indicates active viral replication?

Accepted Answer

HBsAg (hepatitis B surface antigen)

Answer

Anti-HBs (hepatitis B surface antibody)

Answer

Anti-HBc IgG

Answer

HBeAg (hepatitis B e antigen)

Question 6

In latex agglutination tests, patient antibodies cause visible clumping because:

Accepted Answer

Latex beads coated with antigen cross-link with specific antibodies

Answer

Antibodies activate complement on the latex surface

Answer

Latex particles bind complement and precipitate

Answer

Antibodies dissolve the latex polymer matrix

Question 7

A four-fold or greater rise in antibody titer between acute and convalescent serum samples is considered diagnostically significant because it:

Accepted Answer

Indicates a current or recent active infection rather than past exposure

Answer

Rules out a prior infection with the same organism

Answer

Confirms the patient has developed immunity

Answer

Demonstrates a class switch from IgM to IgG