type 2 cytokine serum levels in healthy sickle cell ...

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Stephen C. Taylor, MD, Samuel J. Shacks, PhD, MD, Zengwei Qu, and Paul Wiley ... From the Department of Pediatrics, Charles R. Drew University of. Medicine ...
TYPE 2 CYTOKINE SERUM LEVELS IN HEALTHY SICKLE CELL DISEASE PATIENTS Stephen C. Taylor, MD, Samuel J. Shacks, PhD, MD, Zengwei Qu, and Paul Wiley Los Angeles, California

Sickle cell disease (SCD) is characterized by significant morbidity and early mortality. Children with this hemoglobinopathy exhibit many of the manifestations associated with immunodeficiency disorders. Serum was obtained from 56 healthy SCD subjects and 45 normal healthy controls. Type 2 cytokines interleukin (IL)-4, IL-6, and IL-10 serum levels were measured. Concentrations were determined by reference to a standard curve, and results were expressed in pg/mL. Results revealed significant levels of IL-4 in 6 (13%) of 45 SCD patients compared with 1 (2%) of 45 controls. Increased levels of IL-6 were present in 35 (78%) of 45 SCD patients and 12 (41%) of 29 controls. Elevated levels of IL-10 were detectable in 13 (41%) of 42 SCD patients and 1 (4%) of 25 controls. High circulating levels of type 2 cytokines may suppress both humoral and cell-mediated immune functions in SCD, with resultant increased morbidity. (J Natl Med Assoc. 1 997;89:753-757.)

Key words: cytokines * sickle cell disease

Sickle cell disease (SCD) is one of the oldest prototypical molecular diseases; however, it frequently is considered only as a hematological disorder.'-5 The clinical course of SCD is well-chronicled in the literature.6-'2 Patients with SCD have a compensated state of ill health or steady state interspersed with periods of acute exacerbation called crises. These periods of crisis are characterized as anemic or painful (vaso-occlusive) and are associated with infection more than any other predisposing event. In addition, the high predilection for frequent and severe bacterial infections in SCD is highly suggestive of known immunocompromised states.'317 Historically, the abnormalities described to From the Department of Pediatrics, Charles R. Drew University of Medicine and Science, King-Drew Medical Center, Los Angeles, California. This work was supported by National Institutes of Health grant no. GM08140-21. Requests for reprints should be addressed to Dr Stephen C. Taylor, Dept of Pediatrics, Charles R. Drew University of Medicine and Science, King-Drew Medical Ctr, 12021 S Wilmington Ave, Los Angeles, CA 90059. JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION, VOL. 89, NO. 11

explain the increased susceptibility to bacterial infections include splenic hypofunction, humoral dysfunction, opsonophagocytic defects, and alternate pathway of complement defects. 18-21 The study described here assesses in vivo production of type 2 cytokines during the healthy state of SCD compared with healthy normal controls and offers further evaluation of SCD as a model for immunodysfunction.

MATERIALS AND METHODS Study Population The study population consisted of 56 SCD patients in the steady state of disease. Patient ages ranged from 1 to 17 years. The SCD subjects were comprised of 52 patients with sickle cell anemia, 2 patients with sickle cell-hemoglobin C disease, and 2 patients with sickle cell-thalassemia disease. All of the SCD patients underwent follow-up at the Pediatric Hematology Clinic, King-Drew Medical Center. Sickle cell disease patients were crisis-free at least 1 month before entrance into the study. Forty-five control patients without SCD were matched for age and gender. All of the patients in the SCD group were black, whereas the control group was comprised of 65% black and 753

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plate was incubated for 1 hour at 37°C. Unbound material was then removed by aspiration and washing. Next, conjugate reagent was added, and the plate was incubated for 30 minutes. After incubation, unbound labeled antibody in the conjugate reagent was removed by aspiration and washing. The bound IL-4, IL-6, or IL-10 was quantified by an enzymatic reaction, resulting in a detectable color change using an ELISA reader (Titertek Multiskan, Flow Laboratories Inc, McLean, Virginia) set at 450 nm. To estimate the amount of IL-4, IL-6, or IL-10 in the serum, a standard curve was constructed using known standard concentrations. Concentrations of samples were determined by referring to the standard curve and were expressed as pg/mL. The usual normal range for serum samples in healthy individuals, as per the manufacturer, is IL-4