Clinical Observations, Plasma Retinol Concentrations, and In Vitro Lymphocyte Functions in Children With Sickle Cell Disease

Abstract

Background: Children with sickle cell disease (SCD) often have infections, growth deficits, and impaired immunity, problems that also are observed in individuals with a vitamin A deficiency (plasma retinol concentration <20 μg/dL). The goal of this study was to investigate the association between vitamin A, health status, and the in vitro immune function of children with SCD. Methods: Fifty-nine children (40 SS, 11 SC, and 8 Sβ thalassemia [Sβ thal ] hemoglobin genotypes) 9 months to 18 years old were investigated for plasma levels of retinol, retinol binding protein, C-reactive protein, alpha-1-acid glycoprotein, lymphocyte proliferation, and interleukin (IL)-2 activity in supernatant of phytohemagglutinin-treated lymphocytes. Results: The plasma retinol concentrations of children with SCD (mean 57.6 μg/dL, range 4.6-116 μg/dL) were not different from those of 21 normal individuals (mean 62 μg/dL, range 28.7-162 μg/dL). Plasma retinol concentrations did not vary by hemoglobin genotype but were lower in boys than in girls (P < 0.05) and were also lower in children with inflammation (P = 0.1). Seven children (11.9%) (6 HbSS, 1 HbSβ 0thal ) were vitamin A-deficient, and 9 children (15.3%) had suboptimal vitamin A status (plasma retinol concentration of 20-29 μg/dL). Children with vitamin A deficiency had slightly lower height (P = 0.09) and weight mean percentiles, lymphocyte proliferative responses, and IL-2 activity (P > 0.1), but higher means of C-reactive protein (P = 0.05), pain crisis episodes and inflammation (P = 0.1), and health scores (P > 0.1) than children who were not vitamin A-deficient. Lymphocyte proliferative responses negatively correlated with health score, pain crisis episodes, and blood units received, but positively correlated with retinol binding protein (P < 0.05 to P = 0.1). Conclusion: Identification and correction of suboptimal vitamin A status in children with SCD may improve immunity and attenuate certain health complications associated with this disease.

In Vitro Lymphocyte Functions in Undernourished Children With Sickle Cell Anemia

“…14,16,17 We have observed that lymphocyte proliferation and IL-2 secretion tend to be lower in children with SCD who have suboptimal vitamin A status vs those with adequate plasma retinol levels. 19 In a previous small study, we reported that nearly 53% of the children with SCD had plasma levels of retinol-binding protein (RBP) <30 mg/L, but no child had albumin (Alb) levels <35 g/L. 20 The study suggested the presence of mild to moderate PEM in our SCD patient population.…”

“…We do not believe that vitamin A status is the main factor in the association between low lymphocyte proliferative responses to PHA concentration and low RBP level because of the expected low prevalence of vitamin A deficiency in our patients as we previously reported. 19 5. In parallel to the poorer nutritional status of children with HbSS/HbSβ°genotypes, their in vitro lymphocyte functions also were poorer than those of children with HbSC.…”

“…Our data on inflammatory cytokines (TNF-α), the association between vascular cell adhesion molecule-1 and zinc levels, lymphocyte proliferation as a function of plasma retinol concentration, and clinical status have been previously published. 18,19,21 Inclusion criteria were boys and girls with HbSS, HbSC, and/or HbSβ thalassemia (HbSβ thal-0 ) genotypes who were 0.5 to 18 years old. Exclusion criteria were children who (1) were on hydroxyurea at the time of recruitment, (2) had received a bone marrow transplant, (3) had had a splenectomy, and (4) were hospitalized at the time of blood drawing.…”

“…Details for the isolation of mononuclear cells and culture conditions for lymphocyte proliferation have been previously described. 19,27 The culture medium contained RPMI-1640, 10% heat-inactivated human AB serum, 5 × 10 4 units penicillin, 50 mg streptomycin, 1 mmol sodium pyruvate, 0.1 mmol nonessential amino acids, 2 mmol L-glutamine, and 50 μmol β-mercaptoethanol (per 1,000 mL). Lymphocyte proliferation (of triplicate cultures containing 2 × 10 5 viable cells/200 μL medium) was assessed by the rate of 3 H-thymidine incorporated into DNA.…”

“…Macrocultures (2 × 10 6 viable cells/mL) containing 0 to 20 μg PHA were incubated at 37°C and 5% CO 2 in a humidified atmosphere. 19,28 After 48 hours, cultures were centrifuged, and the supernatant was collected and immediately frozen at -70°C. The IL-2 activity in the supernatant was estimated by the growth rate of IL-2-dependent CTLL-2 cells assessed by 3 H-thymidine uptake.…”