Cytokines, a diverse group of proteins and peptides secreted by many cells (e.g., lymphocytes, T cells, monocytes, B cells, eosinophils), respond to an immunologic challenge. They are involved in immunity, allergy, and long-term memory (i.e., degenerative aspects of aging) and include interferons, interleukins, chemokines, inflammatory cytokines, and hematopoietic growth factors. Cytokines have been directly implicated in a number of diseases, such as asthma, interstitial cystitis, RA, septic shock, transplant rejection, cirrhosis, and multiple sclerosis. Most interleukins are produced by macrophages and lymphocytes. Interleukins need adequate amounts of fats and pyridoxine to be effective. Some, such as IL-3, are involved in fever, slow-wave sleep, bone resorption, and use of protein by muscles.

These tests are done to evaluate allergy, skin hypersensitivity, asthma, fever, inflammation, and healing. They are also used as tumor markers and to assess immune factors and rheumatic disorders.

1. IL-1:

   1. 3, 5, 7, 9, 11, 12, 13, 14, 15, 16, 17, and 18

   2. Normal: Physiologic levels are normally very low (few pg/mL or ng/L).

2. IL-1a:

   1. Plasma: 0.1 ± 1.4 pg/mL or ng/L

   2. Urine median: 1–4 pg/μmol creatinine or μg/mol creatinine

3. IL-1b:

   1. Blood: 4.60 ± 300 pg/mL or ng/L

   2. Serum: 0.07 ± 0.02 ng/mL or μg/L

4. IL-2:

   1. Amniotic fluid (AMF): Median, 1.35 ng/mL or 1.35 μg/L

   2. Plasma: 0.3 ± 0.47 pg/mL or 0.3 ± 0.5 ng/L

5. IL-4:

   1. Serum: 0.75 ± 0.1 ng/mL or 0.75 ± 0.10 μg/L

   2. See eosinophil count; T cells stimulate eosinophil production

6. IL-6:

   1. Urine: 237 ± 92 ng/L or 237 ± 92 μg/L

   2. Blood: 1609 ± 710 pg/mL or 1.61 ± 0.71 μg/L

   3. Plasma: 2.50 ± 0.35 pg/mL or 2.50 ± 0.55 ng/L

   4. Serum: 0.4–2.1 pg/mL or 0.4–2.1 ng/L

   5. CSF: 0.04–12.5 ng/mL or 0.0–12.5 μg/L

7. IL-10:

   1. Serum: 0.44 ± 9.5 ng/mL or 44 ± 10 μg/L

   2. AMF: <40 pg/mL or <40 ng/L

8. IL-8:

   1. AMF: 237 ± 92 ng/L or same

9. Chemokines:

   1. Feces: <22–4077 pg/g wet stool or 0.02–4.08 ng/g wet stool

   2. Plasma: 3.3 ± 0.3 pg/mL or ng/L

10. Tumor necrosis factors:

    1. CSF: 22.3 ± 9.5 pg/mL or 1.31 ± 0.56 pmol/L

    2. Feces: <1–231 pg/g wet stool or <1–231 ng/g wet stool

    3. Plasma: 6.4 ± pg/mL or 6.4 ± 4.6 ng/L

    4. Serum: 0.12 ± 0.02 ng/mL or 7.0 ± 1.2 nmol/L

11. Interferon gamma:

    1. Serum (S): 0.7 ± 1.8 pg/mL or 0.7 ± 1.8 ng/L

    2. Plasma (P): 3 ± 1 IU/mL or 3 ± 1 kIU/L

1. Collect a stool, urine, or venous blood sample for serum analysis.

2. Cells from synovial fluid, bronchial secretions, AMF, and CSF may also be tested.

1. Pathophysiologic blood levels may indicate inflammation or cancer. Increases are associated with severity of disease.

2. Elevated levels in synovial fluid, CSF, AMF, urine, feces, and bronchoalveolar fluid may indicate immune disorders, SLE, and other pathologic or degenerative conditions.

Pretest Patient Care

1. Explain the purpose, procedure, benefits, and risks for cytokine tests and the complexities involved. For specimens other than plasma or serum, refer to specific chapters regarding specimen collection and patient care (e.g., urine in Chapter 3, spinal fluid in Chapter 5, AMF in Chapter 15, and stool [feces] in Chapter 4).

2. Obtain properly signed informed consent when necessary (e.g., spinal fluid sample collection). Explain that a local anesthetic will be injected into the skin. Assess for any previous reactions to any numbing or local anesthetic medicines.

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

1. Cytokines can continue to be produced after sample collection by the various cells in the fluid, urine, or feces.

2. Collection tubes can become contaminated by microorganisms, a potent stimulus of cytokine production.

3. Cytokines can degrade in the collection container.

4. Cytokines can bind to cell receptors during storage.

5. Circadian rhythms may affect results.