Five classes of immunoglobulins (antibodies)—IgA, IgG (with four subclasses, IgG₁, IgG₂, IgG₃, and IgG₄), IgM, IgD, and IgE—have been isolated. Immunoglobulins function to neutralize toxic substances, support phagocytosis, and destroy microorganism functions. IgA takes two forms: serum and secretory. Serum IgA is present in blood serum; secretory IgA is found in saliva, tears, colostrum, and bronchial, gastrointestinal, and genitourinary secretions, where it can protect against microorganism invasion. IgE is involved in allergic reactions, whereas IgD is involved in humoral immunity.

IgG, the only immunoglobulin that can cross the placenta, is responsible for protection of the newborn during the first months of life. IgM possesses antibody activity against Gram-negative organisms and RFs and forms natural antibodies such as the ABO blood group. IgM does not cross the placenta and is therefore usually absent in the newborn. It is observed about 5 days after birth.

Quantitative immunoglobulin measurements can monitor the course of a disease and its treatment. If there is a monoclonal protein or M component present on serum protein electrophoresis (SPEP), a quantitative measurement of IgA, IgG, and IgM can identify the specific immunoglobulin. IgD and IgE are present in trace amounts.

These values are derived from rate nephelometry.

1. Adults:

   1. IgG: 700–1500 mg/dL or 7.0–15.0 g/L

   2. IgA: 60–400 mg/dL or 600–4000 mg/L

   3. IgM: 60–300 mg/dL or 600–3000 mg/L

   4. IgE: 3–423 IU/mL or 3–423 kIU/L

   5. IgD: 0–14 mg/dL or 0–140 mg/L

2. Children:

   1. IgG (boys and girls):

      1. 0–4 months: 141–930 mg/dL or 1.4–9.3 g/L

      2. 5–8 months: 250–1190 mg/dL or 2.5–11.2 g/L

      3. 9–11 months: 320–1250 mg/dL or 3.2–12.5 g/L

      4. 1–3 years: 400–1250 mg/dL or 4.0–12.5 g/L

      5. 4–6 years: 560–1307 mg/dL or 5.6–13.1 g/L

      6. 7–9 years: 598–1379 mg/dL or 6.0–13.8 g/L

      7. 10–12 years: 638–1453 mg/dL or 6.4–14.5 g/L

      8. 13–15 years: 680–1531 mg/dL or 6.8–15.3 g/L

      9. 16–17 years: 724–1611 mg/dL or 7.2–16.1 g/L

   2. IgA (boys and girls):

      1. 0–4 months: 6–64 mg/dL or 60–640 mg/L

      2. 5–8 months: 10–87 mg/dL or 100–870 mg/L

      3. 9–14 months: 17–94 mg/dL or 170–940 mg/L

      4. 15–23 months: 20–175 mg/dL or 200–1750 mg/L

      5. 2–3 years: 24–192 mg/dL or 240–1920 mg/L

      6. 4–6 years: 26–232 mg/dL or 260–2320 mg/L

      7. 7–9 years: 33–258 mg/dL or 330–2580 mg/L

      8. 10–12 years: 45–285 mg/dL or 450–2850 mg/L

      9. 13–15 years: 47–317 mg/dL or 470–3170 mg/L

      10. 16–17 years: 55–377 mg/dL or 550–3770 mg/L

   3. IgM (boys):

      1. 0–4 months: 14–142 mg/dL or 140–1420 mg/L

      2. 5–8 months: 24–167 mg/dL or 240–1670 mg/L

      3. 9–23 months: 35–200 mg/dL or 350–2000 mg/L

      4. 2–3 years: 41–200 mg/dL or 410–2000 mg/L

      5. 4–17 years: 55–260 mg/dL or 550–2600 mg/L

   4. IgM (girls):

      1. 0–4 months: 14–142 mg/dL or 140–1420 mg/L

      2. 5–8 months: 24–167 mg/dL or 240–1670 mg/L

      3. 9–23 months: 35–242 mg/dL or 350–2420 mg/L

      4. 2–3 years: 41–250 mg/dL or 410–2500 mg/L

      5. 4–17 years: 56–260 mg/dL or 560–2600 mg/L

1. Collect a 7-mL blood serum sample in a red-topped tube. Observe standard precautions.

2. Label the specimen with the patient’s name, date, and test(s) ordered and place in a biohazard bag for transport to the laboratory.

1. IgA accounts for 10%–15% of total immunoglobulin. Increases occur in the following conditions or situations:

   1. Chronic, nonalcoholic liver diseases, especially primary biliary cirrhosis (PBC)

   2. Obstructive jaundice

   3. Exercise

   4. Alcoholism

   5. Subacute and chronic infections

2. IgA decreases occur in the following conditions or situations:

   1. Ataxia telangiectasia

   2. Chronic sinopulmonary disease

   3. Congenital deficit

   4. Late pregnancy

   5. Prolonged exposure to benzene immunosuppressive therapy

   6. Abstinence from alcohol after a period of 1 year

   7. In the presence of certain drugs and dextrin

   8. Protein-losing gastroenteropathies

3. IgG constitutes 75%–80% of total immunoglobulins. Increases occur in the following conditions:

   1. Chronic granulomatous infections

   2. Hyperimmunization

   3. Liver disease

   4. Malnutrition (severe)

   5. Dysproteinemia

   6. Disease associated with hypersensitivity granulomas, dermatologic disorders, and IgG myeloma

   7. RA

4. IgG decreases occur in the following conditions:

   1. Agammaglobulinemia

   2. Lymphoid aplasia

   3. Selective IgG, IgA deficiency

   4. IgA myeloma

   5. Bence Jones proteinemia

   6. Chronic lymphoblastic leukemia

5. IgM constitutes 5%–10% of total antibody. Increases in adults occur in the following conditions:

   1. Waldenström macroglobulinemia

   2. Trypanosomiasis

   3. Malaria

   4. IM

   5. Lupus erythematosus

   6. RA

   7. Dysgammaglobulinemia (certain cases)

6. IgM decreases occur in the following conditions:

   1. Agammaglobulinemia

   2. Lymphoproliferative disorders (certain cases)

   3. Lymphoid aplasia

   4. IgG and IgA myeloma

   5. Dysgammaglobulinemia

   6. Chronic lymphoblastic leukemia

Pretest Patient Care

1. Explain test purpose and specimen collection procedure.

2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.