Free Medical Laboratory Technician Immunology and Serology Questions and Answers — Questions and Answers
Question 1: A patient presents with severe allergies, including hay fever and asthma. An elevation of which immunoglobulin class is most strongly associated with this type of Type I hypersensitivity reaction?
- IgA
- IgG
- IgE (Correct answer)
- IgM
Correct answer: IgE
Immunoglobulin E (IgE) is the primary antibody involved in Type I hypersensitivity reactions, also known as immediate or allergic reactions. IgE antibodies bind to the surface of mast cells and basophils. Upon re-exposure to a specific allergen, the allergen cross-links the IgE molecules, triggering the degranulation of these cells and the release of histamine and other inflammatory mediators, causing allergic symptoms.
Question 2: A 19-year-old college student presents with fatigue, sore throat, and lymphadenopathy. A monospot test for heterophile antibodies is positive. This result is most consistent with an acute infection caused by which of the following viruses?
- Cytomegalovirus (CMV)
- Epstein-Barr virus (EBV) (Correct answer)
- Rubella virus
- Varicella-zoster virus (VZV)
Correct answer: Epstein-Barr virus (EBV)
Infectious mononucleosis is most commonly caused by the Epstein-Barr virus (EBV). EBV infection induces the production of heterophile antibodies, which are detected by rapid monospot tests. While other viruses like CMV can cause a mononucleosis-like illness, they are typically associated with a negative heterophile antibody test.
Question 3: In a sandwich enzyme-linked immunosorbent assay (ELISA) designed to detect a specific antigen, what is the final component added that directly interacts with an enzyme to produce a measurable color change?
- A chromogenic substrate (Correct answer)
- The patient's antigen
- A secondary (detection) antibody
- A capture antibody
Correct answer: A chromogenic substrate
In a sandwich ELISA, the final step to generate a signal involves adding a chromogenic substrate. The detection antibody is conjugated to an enzyme (like HRP). This enzyme catalyzes a reaction with the substrate, causing it to change color. The intensity of the color is proportional to the amount of antigen present.
Question 4: The classical pathway of the complement system is primarily initiated by the binding of C1q to which of the following?
- Bacterial endotoxins (LPS)
- Mannose-binding lectin on pathogen surfaces
- Antigen-antibody complexes (Correct answer)
- Spontaneously hydrolyzed C3
Correct answer: Antigen-antibody complexes
The classical pathway of complement activation is a key link between the innate and adaptive immune systems. It is typically initiated when the C1q component of the C1 complex binds to the Fc portion of IgG or IgM antibodies that have formed a complex with an antigen.
Question 5: A medical laboratory technician performs a Rapid Plasma Reagin (RPR) test on a patient's serum. The test slide shows visible black clumps against the white background of the card. How should this result be interpreted?
- Non-reactive, indicating the absence of treponemal antibodies
- Invalid, as the carbon particles have precipitated
- Reactive, indicating the presence of non-treponemal (reagin) antibodies (Correct answer)
- Positive for neurosyphilis
Correct answer: Reactive, indicating the presence of non-treponemal (reagin) antibodies
The RPR test is a non-treponemal flocculation test used to screen for syphilis. The antigen suspension contains cardiolipin coated with carbon particles. If the patient's serum contains reagin antibodies, they will bind to the cardiolipin, causing the carbon particles to flocculate or clump together, which appears as black clumps. This is interpreted as a reactive result.
Question 6: A physician suspects a patient has systemic lupus erythematosus (SLE). While an ANA test is a sensitive screening test, which of the following autoantibodies is considered highly specific for SLE and is a key component of its diagnostic criteria?
- Rheumatoid Factor (RF)
- Anti-double-stranded DNA (anti-dsDNA) (Correct answer)
- Anti-mitochondrial antibody (AMA)
- Anti-cyclic citrullinated peptide (Anti-CCP)
Correct answer: Anti-double-stranded DNA (anti-dsDNA)
Anti-double-stranded DNA (anti-dsDNA) antibodies are highly specific for systemic lupus erythematosus (SLE). While not present in all SLE patients, their presence strongly supports the diagnosis. Anti-Sm is another highly specific antibody, whereas RF and Anti-CCP are associated with rheumatoid arthritis, and AMA is associated with primary biliary cholangitis.
