Immunoglobulins are serum antibodies produced by the plasma cells of the B lymphocytes. Immunoglobulins (Ig) have been subdivided into the five classes: IgG, IgA, IgM, IgD, and IgE. Their functions are listed in Table 3-3. IgG, IgA, and IgM have been further divided into subclasses: IgG₁, IgG₂, IgG₃, and IgG₄.

Four techniques can be used to assess Ig: (1) serum protein electrophoresis, (2) immunoelectrophoresis, (3) radial immunodiffusion, and (4) radioimmunoassay. Serum protein electrophoresis, although not specific to the immunoglobulins, may indicate the presence of immunologic disorders such that additional testing may not be needed. Electrophoresis separates the serum proteins into albumin and globulin components, with the latter being further broken down into ₁, ₂, , and fractions. Most of the fraction derives from IgG molecules, whereas IgM contributes to the portion.¹⁸

Three types of alterations in immunoglobulins can be identified by serum protein electrophoresis: (1) hypogammaglobulinemia, a reduction in the total quantity of immunoglobulins; (2) monoclonal gammopathy, excessive amounts of single immunoglobulins or proteins related to immunoglobulins (seen in multiple myeloma and macroglobulinemia); and (3) polyclonal gammopathy, excessive amounts of several different immunoglobulins (seen in many infections and diffuse inflammatory conditions).^19,20 Examples of these serum protein electrophoretic patterns are diagrammed in Figure 3-5. Additional examples of disorders associated with monoclonal and polyclonal gammopathies are listed in Table 3-4.

Immunoelectrophoresis is not a quantitative technique, but it provides such detailed separation of the individual immunoglobulins that modest deficiencies are readily detected. It identifies the presence of monoclonal protein and its type. Radial immunodiffusion allows measurement of the quantity of individual immunoglobulins to concentrations as low as 10 to 20 mg/dL. Radioimmunoassay provides better results when immunoglobulin levels are below 20 mg/dL. Serum IgD and IgE are normally well below this level, as are immunoglobulin levels in most body fluids other than serum.

Cryoglobulin is an immunoglobulin that precipitates in the cold and, in those who develop high concentrations, causes the blockage of small capillaries in fingers, ears, and toes exposed to cold temperatures. The test is performed by first cooling the blood serum in a refrigerator to note whether a precipitate forms in 2 to 7 days and then measuring the volume in relation to the percentage of the total serum to obtain a numerical value analogous to a hematocrit. Three positive types of cryoglobulins can be identified by immunoelectrophoresis. Pyroglobulin is a protein identified by heating the blood serum to obtain a precipitate, indicating an abnormality. The test is performed to determine cold sensitivity as well as to assist in the diagnosis of collagen disorders, malignancies, or infections.²¹

Percentage of Total Protein

Serum Protein Electrophoresis	Conventional Units	SI Units
Constituent
Albumin	52-68	0.520-0.680
Globulin	32-48	0.320-0.480
1-Globulin	2.4-5.3	0.024-0.053
2-Globulin	6.6-13.5	0.066-0.135
-Globulin	8.5-14.5	0.085-0.145
-Globulin	10.7-21.0	0.107-0.210

• Immunizations within 6 months before the test may alter test results.
• Transfusions of either whole blood or fractions within 2 months may alter test results.

• Suspected immunodeficiency, either congenital or acquired
• Suspected immunoproliferative disorders such as multiple myeloma or Waldenström's macroglobulinemia
• Suspected autoimmune disorder
• Suspected malignancy involving the lymphoreticular system
• Monitoring of effects of chemotherapy or radiation therapy, or both, which may suppress the immune system
• Identification of hypogammaglobulinemia, monoclonal gammopathy, and polyclonal gammopathy by serum protein electrophoresis (see Fig. 3—5 and Table 3-4)
• Support for diagnosing a variety of disorders associated with altered immunoglobulin levels (see Table 3-3)

Nursing Care Before the Procedure

Client preparation is the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).

• The client should be interviewed to determine whether he or she has received immunizations within 6 months before the test or transfusions of whole blood or fractions within 2 months before the test.

A venipuncture is performed and the sample collected in a red-topped tube or other type of blood collection tube, depending on laboratory preference. The sample should be transported to the laboratory promptly.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample.

• Because the client may be immunosuppressed, assess the site for signs of infection.
• Complications and precautions: Note and report abnormal levels in relation to immunodeficiency, malignant, or autoimmune disorders.