MLPAO MLPAO Immunology and Serology 3

Question 1

Rheumatoid factor (RF) is typically an autoantibody of which immunoglobulin class directed against:

Accepted Answer

IgM directed against patient's own IgG

Answer

Rheumatoid factor is classically an IgM autoantibody that targets the Fc region of the patient's own IgG, forming immune complexes that contribute to inflammation in rheumatoid arthritis.

Question 2

In flow cytometry, CD4:CD8 ratio is used clinically to monitor patients with HIV. A significantly decreased ratio (below 1.0) indicates:

Accepted Answer

Progressive immunodeficiency due to CD4+ T cell depletion

Answer

HIV selectively destroys CD4+ T helper cells, causing the CD4:CD8 ratio to fall below normal (normal ~2:1); a ratio below 1.0 indicates significant immune compromise and disease progression.

Question 3

The Weil-Felix test uses Proteus vulgaris antigens to detect antibodies in patients suspected of having:

Accepted Answer

Rickettsial infections

Answer

The Weil-Felix test exploits cross-reactive antigens between Rickettsia species and certain Proteus strains; patient antibodies from rickettsial infections agglutinate Proteus OX-19, OX-2, and OX-K antigens.

Question 4

Which principle underlies the fluorescent treponemal antibody absorption (FTA-ABS) test for syphilis?

Accepted Answer

Indirect immunofluorescence after absorption of non-specific antibodies

Answer

The FTA-ABS uses indirect immunofluorescence where patient serum is first absorbed with non-pathogenic treponemes to remove cross-reactive antibodies, then applied to Treponema pallidum on a slide and detected with fluorescent anti-human immunoglobulin.

Question 5

In immunofixation electrophoresis (IFE) for serum protein analysis, a monoclonal band (M-protein) in the gamma region most commonly suggests:

Accepted Answer

A plasma cell dyscrasia such as multiple myeloma

Answer

A discrete monoclonal band (M-spike) on IFE indicates clonal proliferation of a single plasma cell line producing identical immunoglobulin, characteristic of plasma cell dyscrasias including multiple myeloma and Waldenström macroglobulinemia.

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO MLPAO Immunology and Serology 3