6 IMMUNOGLOBULINS, COMPLEMENT, AND CELLULAR TESTING Flashcards
(1) Which of the following symptoms in a young child may indicate an immunodeficiency syndrome?
A. Anaphylactic reactions
B. Severe rashes and myalgia
C. Recurrent bacterial, fungal, and viral infections
D. Weight loss, rapid heartbeat, breathlessness
C. Recurrent bacterial, fungal, and viral infections
An immunodeficiency syndrome should be considered in a young child who has a history of recurrent bacterial, fungal, and viral infections manifested after the disappearance of maternal IgG. Immunodeficiency disorders may involve deficiencies in production and/or function of lymphocytes and phagocytic cells or a deficiency in production of a complement factor. Choice of laboratory tests is based on the patient’s clinical presentation, age, and history.
(2) What screening test should be performed first in a young patient suspected of having an immune dysfunction disorder?
A. Complete blood count (CBC) and WBC differential
B. Chemotaxis assay
C. Complement levels
D. Bone marrow biopsy
A. Complete blood count (CBC) and WBC differential
The first screening tests performed in the initial evaluation of a young patient who is suspected of having an immune dysfunction are the CBC and differential. WBCs that are decreased in number or abnormal in appearance may indicate further testing.
(3) Which test should be performed when a patient has a reaction to transfused plasma products?
A. Ig levels
B. T-cell count
C. Hemoglobin levels
D. RBC enzymes
A. Ig levels
A reaction to plasma products may be found in an IgA-deficient person who has formed anti-IgA antibodies. Ig levels would aid in this determination. Selective IgA deficiency is the most common immunodeficiency disease and is characterized by serum IgA levels below 5 mg/dL. IgA is usually absent from secretions, but the B-cell count is usually normal.
(4) What is the “M” component in monoclonal gammopathies?
A. IgM produced in excess
B. Heavy chain produced in excess
C. Malignant proliferation of B cells
D. Monoclonal antibody or cell line
D. Monoclonal antibody or cell line
The “M” component refers to any monoclonal protein or cell line produced in a monoclonal gammopathy, such as multiple myeloma.
(5) A child suspected of having an inherited humoral immunodeficiency disease is given diphtheria/tetanus vaccine. Two weeks after the immunization, his level of antibody to the specific antigens is measured. Which result is expected for this patient if he, indeed, has a humoral deficiency?
A. Increased levels of specific antibody
B. No change in the level of specific antibody
C. An increase in IgG-specific antibody but not IgM specific antibody
D. Increased levels of nonspecific antibody
B. No change in the level of specific antibody
In a patient with immunodeficiency, the expected levels of specific antibody to the antigens in the vaccine would be decreased or not present. This response provides evidence of deficient antibody production.
(6) Which disease may be expected to show an IgM spike on an electrophoretic pattern?
A. Hypogammaglobulinemia
B. Multicystic kidney disease
C. Waldenström macroglobulinemia
D. Wiskott-Aldrich syndrome
C. Waldenström macroglobulinemia
Waldenström macroglobulinemia is a malignancy of plasmacytoid lymphocytes involving both bone marrow and lymph nodes. The malignant cells secrete monoclonal IgM and are in transition from B cells to plasma cells. In contrast to multiple myeloma, osteolytic bone lesions are not found.
(7) In testing for DiGeorge syndrome, what type of laboratory analysis would be most helpful in determining the number of mature T cells?
A. CBC
B. Dihydrorhodamine reduction (DHR) test
C. T-cell mitogen assays
D. Flow cytometry
D. Flow cytometry
DiGeorge syndrome is caused by a developmental failure or hypoplasia of the thymus and results in deficiency of T lymphocytes and cell-mediated immune function. The T-cell count is low, but the level of Igs is usually normal. Flow cytometry is most helpful in determining numbers and subpopulations of T cells.
(8) Interpret the following description of an IFE assay of urine. Dense wide bands in both the κ- and λ-lanes. No bands present in the heavy-chain lanes.
A. Normal
B. Light-chain disease
C. Increased polyclonal Fab fragments
D. Multiple myeloma
C. Increased polyclonal Fab fragments
Heavy wide bands seen with both anti-κ and anti-λ antisera indicate excessive polyclonal light-chain excretion. Light-chain disease would show a heavy restricted band for one of the light-chain reactions, but not both. The finding of excess λ- and κchains indicates a polyclonal gammopathy with increased Ig turnover and excretion of the light chains as Fab fragments.
(9) Free monoclonal light chains are often present in the serum of patients with multiple myeloma and may be useful for disease monitoring. Which of the following assays would be recommended to detect the presence of free light chains in serum?
A. SPE
B. Urine immunofixation
C. Nephelometry
D. ELISA
C. Nephelometry
Free light chains in serum are a sensitive indicator of a monoclonal gammopathy. They are often not present in sufficient quantity to show a band on a protein electrophoresis gel. Detecting light chains in urine is not an indicator of what the serum levels may be. Serum Ig heavy and light chains are most commonly measured by using rate or endpoint nephelometry. ELISA assays are most often used to measure specific antibody levels, not to quantitate Ig heavy- or light-chain isotypes.
(10) What is measured in the CH50 assay?
A. RBC quantity needed to agglutinate 50% of antibody
B. Complement needed to lyse 50% of RBCs
C. Complement needed to lyse 50% of antibody sensitized RBCs
D. Antibody and complement needed to sensitize 50% of RBCs
C. Complement needed to lyse 50% of antibody sensitized RBCs
CH50 is the amount of complement needed to lyse 50% of standardized antibody-sensitized sheep RBCs. It is expressed as the reciprocal of the serum dilution resulting in 50% hemolysis. Low levels are associated with deficiency of some complement components and active systemic autoimmune diseases in which complement is being consumed.
(11) What type of disorders would show a decrease in C3, C4, and CH50?
A. Autoimmune disorders, such as SLE and RA
B. Immunodeficiency disorders, such as common variable immunodeficiency
C. Tumors
D. Bacterial, viral, fungal, or parasitic infections
A. Autoimmune disorders, such as SLE and RA
The pattern of decreased C3, C4, and CH50 indicates classic pathway activation. This results in consumption of complement and is associated with SLE, serum sickness, subacute bacterial endocarditis, and other immune complex diseases. The inflammatory response seen in malignancy and acute infections gives rise to an increase in complement components. Immunodeficiency caused by an inherited deficiency in complement constitutes only about 1% of immunodeficiency diseases. Such disorders reduce the CH50 but involve a deficient serum level of only one complement factor.
(12) All of the following tests measure phagocyte function except:
A. Leukocyte adhesion molecule analysis
B. DHR assay
C. Nitro blue tetrazolium (NBT) test
D. IL-2 assay
D. IL-2 assay
The DHR assay and the older NBT tests are used to diagnose chronic granulomatous disease, an inherited disorder in which phagocytic cells fail to kill microorganisms because of a defect in peroxide production (respiratory burst). Leukocyte adhesion deficiency is associated with a defect in the production of integrin molecules on the surface of WBCs and their granules. IL-2 is a cytokine produced by activated T-helper and B cells. It causes B-cell proliferation and increased production of antibody, interferon, and other cytokines. IL-2 can be measured by EIA and is used to detect transplant rejection, which is associated with an increase in the serum and urine levels.
