Medical Laboratory Technician Exam Immunology and Serology 5

Question 1

Which type of hypersensitivity reaction is responsible for contact dermatitis caused by poison ivy?

Accepted Answer

Type IV – delayed-type (cell-mediated)

Answer

Contact dermatitis is a Type IV (delayed-type) hypersensitivity reaction mediated by sensitized T lymphocytes, not antibodies.

Question 2

A positive tuberculin (PPD) skin test reaction is read at 48–72 hours and is an example of which immune mechanism?

Accepted Answer

T cell–mediated delayed hypersensitivity

Answer

PPD testing relies on Type IV delayed hypersensitivity; sensitized CD4+ T cells release cytokines causing induration at the injection site.

Question 3

Which of the following is a characteristic of the alternative pathway of complement activation?

Accepted Answer

Is spontaneously activated on microbial surfaces lacking regulatory proteins

Answer

The alternative pathway activates spontaneously via continuous low-level C3 hydrolysis and amplifies on surfaces lacking complement regulatory proteins.

Question 4

Anti-centromere antibodies detected by ANA testing are most specifically associated with which disease?

Accepted Answer

Limited cutaneous systemic sclerosis (CREST syndrome)

Answer

Anti-centromere antibodies are highly specific for limited cutaneous systemic sclerosis (CREST syndrome).

Question 5

In flow cytometry, fluorochromes are excited by which energy source?

Accepted Answer

Laser beam

Answer

Flow cytometers use one or more lasers to excite fluorochromes conjugated to antibodies, and detectors measure emitted fluorescence.

Medical Laboratory Technician Exam Practice Test

Medical Laboratory Technician Exam Practice Test

Medical Laboratory Technician Exam Immunology and Serology 5