Immunoglobulin G responses against falciparum malaria specific antigens are higher in children with homozygous sickle cell trait than those with normal hemoglobin.

BACKGROUND: High Immunoglobulin G (IgG) response to Plasmodium falciparum antigens is associated with partial malaria protection in sickle hemoglobin (HbS) children. However, this response has been more studied in children with heterozygous sickle cell trait (HbAS) but little explored in those with homozygous sickle cell trait (HbSS). The current study was conducted to determine the IgG responses against specific Plasmodium falciparum antigens in children with homozygous sickle cell trait (HbSS) by comparing to those with normal hemoglobin (HbAA). METHODS: A cross sectional study was conducted between April and July 2018 in Dar es Salaam tertiary hospitals. Parents were consented for their child to give about 5 ml of venous blood. IgG concentration from the blood plasma of 220 children (110 HbAA vs. 110 HbSS) were determined using indirect Enzyme Linked Immunosorbent Assay (ELISA). Then IgG medians were compared between the groups with prism 5 software (GraphPad) using Mann Whitney U test. Where the differences in age, hemoglobin levels and body weight between the groups was analyzed using independent sample t test. Multiple linear regressions were used to control cofounding variables such as body weight, age and hemoglobin level using statistical package for social sciences software (SPSS version 23). P value <0.05 was considered statistically significant. RESULTS: The median IgG concentration to PfEBA-175, Pfg27, yPfs28C antigens were HbSS; 20.7 ng/ml (IQR; 18.1-25.6) vs. HbAA; 2.3 ng/ml (IQR; 1.21-3.04), HbSS; 2.76 ng/ml (IQR: 2.08-5.69) vs. HbAA; 1.36 ng/ml (IQR: 1.28-1.76), and HbSS; 26,592 ng/ml (IQR: 10817-41,462) vs. HbAA; 14,164 ng/ml (IQR; 3069-24,302) respectively (p < 0.0001 for all IgG). In both groups; age, body weight and hemoglobin level had no impact on the levels of IgG responses to Plasmodium falciparum antigens except for HbAA group which showed a significant increase in IgG against Pfg27 by 0.004 ng/ml with 1 g/dl increase in Hb level (p = 0.028). CONCLUSIONS: This study found significant higher levels of specific Plasmodium falciparum IgG responses in children with homozygous sickle cell trait than those with normal hemoglobin.

The indirect health effects of malaria estimated from health advantages of the sickle cell trait.

Most estimates of the burden of malaria are based on its direct impacts; however, its true burden is likely to be greater because of its wider effects on overall health. Here we estimate the indirect impact of malaria on children's health in a case-control study, using the sickle cell trait (HbAS), a condition associated with a high degree of specific malaria resistance, as a proxy indicator for an effective intervention. We estimate the odds ratios for HbAS among cases (all children admitted to Kilifi County Hospital during 2000-2004) versus community controls. As expected, HbAS protects strongly against malaria admissions (aOR 0.26; 95%CI 0.22-0.31), but it also protects against other syndromes, including neonatal conditions (aOR 0.79; 0.67-0.93), bacteraemia (aOR 0.69; 0.54-0.88) and severe malnutrition (aOR 0.67; 0.55-0.83). The wider health impacts of malaria should be considered when estimating the potential added benefits of effective malaria interventions.

Complement Levels in Nigeria Patients with Sickle Cell Anaemia in the Asymptomatic State.

OBJECTIVES: Significantly low serum levels of complement components have been reported in patients with Sickle cell anaemia (SCA) which may result in a high susceptibility to infections. However some studies have reported a normal or high complement level. The aim of our study was to assess some haematological parameters and Complement levels in adult patients with steady state SCA in Zaria, North western Nigeria. This will serve as a guide towards infection surveillance in the quest to reduce significant morbidity and mortality in our setting. METHODS: A cross sectional study of 40 patients with SCA in steady state and 40 healthy (non-matched) non-SCA controls at the Haematology clinic of Ahmadu Bello University Teaching Hospital Zaria, was carried out over a 6 month period in 2016. Institutional ethical approval and informed written consentwere obtained. Venous blood was analyzed for haematological parameters by an automated method and complement levels; alternative pathway was assessed by measuring C3, classical pathway by C4 and Terminal pathways by C5 levels using ELISA technique. Data was analyzed with statistical package for social science(SPSS) software version 20.0(2001) and a p value of ≤ 0.05 was considered significant. RESULTS: The age range of patients with SCA and controls were 18 to 46years and 18 to 48years respectively and these were not significantly different p > 0.05. The median levels of C3 (245µg/ml), C4 (245µg/ml) and C5 (40µg/ml) were within normal range in the study subjects but significantly higher (p < 0.05), than those of the controls C3 (165µg/ml), C4 (125µg/ml) and C5(35µg/ml). Haematological parameters showed no correlation with the levels of Complement components studied. CONCLUSION: Although Complement components C3, C4, and C5 levels in patients with SCA are significantly high, the infectious susceptibility may be due to other immunological abnormalities.

Atomic force microscopy: From red blood cells to immunohaematology.

Atomic force microscopy (AFM) offers complementary imaging modes that can provide morphological and structural details of red blood cells (RBCs), and characterize interactions between specific biomolecules and RBC surface antigen. This review describes the applications of AFM in determining RBC health by the observation of cell morphology, elasticity and surface roughness. Measurement of interaction forces between plasma proteins and antibodies against RBC surface antigen using the AFM also brought new information to the immunohaematology field. With constant improvisation of the AFM in resolution and imaging time, the reaction of RBC to changes in the physico-chemistry of its environment and the presence of RBC surface antigen specific-biomolecules is achievable.

Sickle cell trait is associated with controlled levels of haem and mild proinflammatory response during acute malaria infection.

The controlled induction of haemoxygenase-1 (HO-1), an enzyme that catabolizes haem, has been shown to reduce haem, preventing pathologies associated with haem toxicity. The hemoglobin genotype HbAS confers reduced susceptibility to severe complications of malaria by a mechanism that is not well understood. Using a longitudinal approach, we investigated the effect of baseline concentrations of HO-1 on the accumulation of haem during acute Plasmodium falciparum malaria in HbAS and HbAA genotypes. Plasma concentrations of haem, HO-1 and cytokines were quantified in venous blood obtained from children (9 months-5 years of age) during malaria infection, and at convalescence (baseline levels). Parasitaemia was determined during malaria infection. In patients with the HbAA genotype, there was a significant elevation in the plasma concentration of haem (P = 0.002), and a consequent increased induction of HO-1 (P < 0.001) during falciparum malaria compared with levels at convalescence. Contrary to HbAA, plasma concentration of haem did not change in the HbAS genotypical group (P = 0·110), and the induction of HO-1 was reduced during malaria compared with levels at convalescence (P = 0·006). Higher plasma levels of haem were observed in HbAS compared with HbAA at convalescence (P = 0·010), but this difference did not affect the levels of HO-1 within each genotype (P = 0·450). Relatively milder proinflammatory responses were observed in HbAS children during malaria infection compared to HbAA children. Our findings suggest that a mechanism of reduced susceptibility to severe malaria pathologies by the HbAS genotype may involve the control of haem, leading to controlled levels of HO-1 and milder proinflammatory responses during acute malaria.

Estudio seriado de anticuerpos naturales antibanda 3 en enfermos con drepanocitosis / Natural band 3 antibodies follow up study in sickle cell anemia patients

Introducción: Se ha demostrado la participación de moléculas de adhesión, tanto en eritrocitos con hemoglobina SS, como en el endotelio vascular; así como factores plasmáticos en el fenómeno de vasoclusión en la drepanocitosis. La banda 3 se refiere a una familia de intercambiadores aniónicos presentes en la membrana de todas las células y organelos celulares, las que bajo ciertas condiciones se agregan en la superficie del eritrocito y son reconocidos por anticuerpos naturales como parte del mecanismo de eliminación de eritrocitos senescentes u oxidados. Objetivo: Evaluar la posible participación de los anticuerpos naturales antibanda 3 en el fenómeno oclusivo en la drepanocitosis. Métodos: Se realizó la determinación seriada de anticuerpos naturales antibanda 3 en 19 enfermos con drepanocitosis en diferentes estadios clínicos mediante un ensayo inmunoenzimático en microplacas acopladas con la proteína banda 3. Resultados: Se demostró una disminución significativa (p < 0.01) de anticuerpos naturales antibanda 3 en las muestras de los enfermos obtenidas en las fases de crisis vasoclusiva dolorosa, disminución que pudiera estar relacionada con un consumo elevado de estos en el proceso de eliminación de eritrocitos SS oxidados de la circulación sanguínea. Las muestras en estado basal se mantuvieron dentro de los límites normales. Conclusión: Los resultados sugieren la participación de los anticuerpos naturales antibanda 3 como elemento regulador de la no adhesión de los eritrocitos SS al endotelio vascular en esta enfermedad(AU)

Introduction : The involvement of adhesion molecules in erythrocytes with hemoglobin SS, in vascular endothelium and also plasma factors have been shown in the vasoocclusion phenomenon in sickle cell anemia (SCA). Band 3 refers to a family of anion exchangers present in the membrane of all cells and cellular organelles which under certain conditions cluster on the erythrocyte surface being recognized by natural antibodies as part of the mechanism of removal of senescent or oxidized erythrocytes. Objective : To evaluate the possible participation of natural anti band 3 antibodies in the occlusive phenomenon in SCA. Methods : A follow up study to determine the presence of natural band 3 antibodies in 19 patients with SCA in different clinical stages was performed using an enzyme immunoassay in microplates coupled with the band 3 protein. Results : Significant low levels (p<0.01) of natural band 3 antibodies were demonstrated in the samples of patients obtained in painful vasoocclusive crisis stages, decrease which may be related to a high consumption of antibodies in the process of removing oxidized SS erythrocytes from blood circulation. Steady state samples were within normal range. Conclusion: The results suggest the involvement of natural band 3 antibodies in the regulation of the adherence of SS erythrocytes to vascular endothelium in SCA(AU)

Are sickle cell anaemia and sickle cell trait predictive factors for periodontal disease? A cohort study.

BACKGROUND AND OBJECTIVE: Periodontal diseases are associated with bacterial challenge and the host immune response, and are also modulated by genetic factors. There is evidence that sickle cell anaemia (SCA) does not represent a risk factor for periodontal diseases. However, it is still unclear whether the heterozygous condition [sickle cell trait (SCT)] is associated with periodontal diseases. SCT is a genetic condition that can cause vaso-occlusive events, which may be associated with a propensity to bacterial infections. The aim of this study was to investigate the association of SCA and SCT with periodontal diseases by evaluating clinical and radiographic characteristics. MATERIAL AND METHODS: The sample (n = 369) was selected and divided into two groups: exposed groups [HbSS (SCA genotype) and HbAS (SCT genotype) = 246] and a nonexposed group (HbAA = 123). HbAA consisted of individuals without SCA and SCT. The clinical parameters evaluated were plaque index, gingival index, calculus index, clinical probing depth, clinical attachment level, gingival recession, tooth mobility and furcation involvement. The percentage of alveolar bone loss was measured using a Schei ruler. Binomial and Poisson regressions were used to estimate correlations of interest (α = 0.05). RESULTS: None of the periodontal parameters was associated with SCA. SCT was associated with gingivitis (p = 0.041) and periodontitis (p = 0.002). Individuals with SCT had a lower plaque index (p = 0.044) but a higher calculus index (p = 0.003) and greater alveolar bone loss (p = 0.010) compared with subjects in the HbAA group. CONCLUSIONS: SCT can act as a predictor for establishment of periodontal diseases. There was no correlation between SCA and periodontal diseases.

Evidence for both innate and acquired mechanisms of protection from Plasmodium falciparum in children with sickle cell trait.

Sickle cell trait (HbAS) is known to be protective against Plasmodium falciparum malaria, but it is unclear when during the course of infection this protection occurs and whether protection is innate or acquired. To address these questions, a cohort of 601 children 1-10 years of age were enrolled in Kampala, Uganda, and followed for 18 months for symptomatic malaria and asymptomatic parasitemia. Genotyping was used to detect and follow individual parasite clones longitudinally within subjects. Children with HbAS were protected against the establishment of parasitemia, as assessed by the molecular force of infection at older but not younger ages (at 2 years of age: incidence rate ratio [IRR] = 1.16; 95% confidence interval [95% CI], 0.62-2.19; P = .6; at 9 years of age: IRR = 0.50; 95% CI, 0.28-0.87; P = .01), suggesting an acquired mechanism of protection. Once parasitemic, children with HbAS were less likely to progress to symptomatic malaria, with protection again being the most pronounced at older ages (at 2 years of age: relative risk [RR] = 0.92; 95% CI, 0.77-1.10; P = .3; at 9 years of age: RR = 0.68; 95% CI, 0.51-0.91; P = .008). Conversely, the youngest children were best protected against high parasite density (at 2 years of age: relative density = 0.24; 95% CI, 0.10-0.54; P = .001; at 9 years of age: relative density = 0.59; 95% CI, 0.30-1.19; P = .14), suggesting an innate mechanism of protection against this end point.

Differential expression of cytokine genes among sickle-cell-trait (HbAS) and normal (HbAA) children infected with Plasmodium falciparum.

The human immune response to Plasmodium falciparum infection involves the release of cytokines that may contribute to the control of the parasites' replication. These cytokines are also involved in the pathogenesis of the malaria caused by the infection, leading to the appearance of symptoms of varying severity. In a cross-sectional study, the expression of the genes that code for pro-inflammatory cytokines (tumour necrosis factor, interferon-gamma, interleukin-6 and interleukin-12) and anti-inflammatory cytokines (interleukin-10 and interleukin-4) among 80 children infected with P. falciparum (from a malaria-endemic area of Sudan) and five healthy controls (from a non-endemic area) was explored. The infected children were either non-sicklers, with severe malaria (18 children), mild malaria (30) or no symptoms of malaria (18), or asymptomatic sicklers (14). Interleukin-12 was found to be weakly expressed by all the groups of children. In general, compared with the other groups, the asymptomatic non-sicklers had lower expression of all the cytokines studied. The asymptomatic sicklers had significantly lower expression of tumour necrosis factor than the non-sicklers with severe malaria, but these two groups showed similar expression of interferon-gamma, interleukin-4 and interleukin-6. Gene expression of the regulatory cytokine, interleukin-10, by the asymptomatic sicklers was significantly lower than that by the non-sicklers with severe malaria but higher than that recorded in the non-sicklers with mild malaria. Their regulation of cytokine release appears to protect sicklers from clinical malaria.

Immunogenicity and safety of a pneumococcal conjugate 7-valent vaccine in infants with sickle cell disease.

OBJECTIVES: To evaluate safety and immunogenicity of the pneumococcal 7-valent conjugate vaccine (PCV7) when administered to infants with sickle cell disease (SCD) at 2, 3, and 4 months of age with a booster dose of a 23-valent pneumococcal polysaccharide vaccine (PS-23) at 15 to 18 months of age. METHODS: This open-label multicenter study in France enrolled 2-month-old infants with SCD. Blood samples for the determination of antibody concentrations to vaccine serotypes were obtained immediately before and 1 month after the primary immunization, and before and 1 month after the PS-23 booster. Local and systemic reactions were recorded on diary cards. RESULTS: Of the 51 infants enrolled, 49 received primary immunization and 46 received the booster dose. After primary immunization > or =95% of the subjects had antibody titers > or =0.35 microg/mL for the 7 serotypes. After boosting, geometric mean concentrations were high for all serotypes, ranging from 6.32 microg/mL (serotype 18C) to 29.49 microg/mL (serotype 4). Except for 1 case after administration of the booster dose, all fevers reported were less than 39 degrees C. No vaccine-related serious adverse events were reported. CONCLUSIONS: PCV7 administered at 2, 3, and 4 months of age in infants with SCD was well-tolerated, highly immunogenic, and primed for immune memory as indicated by the dramatic response to the PS-23 dose administered at 15-18 months in this study. However, the current recommended schedule is to boost with the PCV7 at 12-15 months of age and for these high-risk children, to enlarge the protection with a subsequent PS-23 dose at 2 years of age.

Correlations between treatment outcome and both anti-MSP119 antibody response and erythrocyte-related genetic factors in Plasmodium falciparum malaria.

Treatment efficacy is related to the interaction of three parameters: drug, parasites, and human factors. The role of human factors in treatment outcome has been poorly documented to date, although human genetic factors and specific immunity have been related to protection against malaria. This study aimed to evaluate a possible cooperation between drug efficacy and host factors in treatment success. The contribution of host factors to treatment efficacy was studied in Gabonese children with a non-severe malaria attack. Children (n=232) aged under 10 years were treated with either sulfadoxine-pyrimethamine or amodiaquine. The influence of erythrocyte-related genetic factors and humoral immune responses (IgG and subclasses) against MSP1(19) on anti-malarial treatment outcome during a 28-day follow-up was studied. Sickle-cell trait carriage and anti-MSP1(19) IgG3 levels were related to lower parasite densities at enrolment (multiple linear regression analysis, P

Distribution of IgG subclass antibodies specific for Plasmodium falciparum glutamate-rich-protein molecule in sickle cell trait children with asymptomatic infections.

Polymorphism in the beta-globin gene (hemoglobin S) has been associated with protection against severe forms of malaria. In a cross-sectional study, 180 young Gabonese children with and without sickle cell trait and harboring asymptomatic Plasmodium falciparum infections, were assessed for the responses to recombinant protein containing the conserved region of glutamate-rich protein (GLURP). We reported increased age-dependence of antibody prevalence and levels of total IgG (p<0.0001), IgG1 (p=0.009), and IgG3 (p<0.03) antibodies to GLURP with a cut-off at 5 years of age. Whatever the hemoglobin type, cytophilic antibodies (IgG1 and IgG3) were prevalent, but GLURP-specific IgG4 antibodies were detected at significantly (p<0.05) lower levels in HbAS children. We showed that the distribution of non-cytophilic IgG antibodies differs according to the hemoglobin type and to the malaria antigens tested. This may have possible implication for the clearance of malaria parasites and for protection against severe malaria.

The sickle cell trait is associated with enhanced immunoglobulin G antibody responses to Plasmodium falciparum variant surface antigens.

The sickle cell trait (HbAS) protects against severe Plasmodium falciparum malaria in young African children. We investigated the extent of the association between HbAS and antibodies directed to parasite-derived variant surface antigens (VSAs) on the membrane of infected erythrocytes. We measured immunoglobulin G (IgG) responses with specificity for VSAs of 2 heterologous parasite isolates in 458 Gabonese children aged between 6 months and 11 years. Logistic regression analyses showed a highly significant independent association (P<.001) between carriage of HbAS and the presence of IgG anti-VSA responses; this association was related specifically to IgG1 and IgG4 subclasses in the anti-VSA profile. IgG2 and IgG3 anti-VSA responses were both independently associated with older age, consistent with the pattern observed in semi-immune adults. The results imply that enhanced levels of cross-reactive anti-VSA responses in children with HbAS may be intimately associated with the protection they have against malaria.

PspA family typing and PCR-based DNA fingerprinting with BOX A1R primer of pneumococci from the blood of patients in the USA with and without sickle cell disease.

Disease and mortality rates for Streptococcus pneumoniae infections are much higher in patients with sickle cell disease (SCD) than in age-matched patients without SCD. Pneumococcal surface protein A (PspA) has been proposed as a component in human vaccines against S. pneumoniae to provide greater breadth of coverage than can be obtained with the 7-valent conjugate vaccine. The cross-reactivity of PspA is associated with the 'PspA family' structure. In this study we examined strains of S. pneumoniae from patients with and without SCD to determine whether the strains infecting the hypersusceptible population of SCD patients were limited to the same two PspA families already known to comprise over 95% of strains infecting non-SCD patients. Each strain was also evaluated according to the presence or absence of specific PCR fragments based on repetitive BOX elements to screen for possible SCD-associated clonal structure. Strains from SCD and non-SCD patients were similarly dispersed among the most common BOX PCR groups and strains from both groups expressed a similar distribution of PspA variants. Thus, a PspA vaccine designed for the population at large should also be appropriate for patients with SCD.

Protection against severe clinical manifestations of Plasmodium falciparum malaria among sickle cell trait subjects is due to modification of the release of cytokines and/or cytoadherence of infected erythrocytes to the host vascular beds.

It is proposed that the surface ligands of Plasmodium falciparum infected HbAS erythrocytes, not like infected HbAA erythrocytes, are altered due to the sickling that soon takes place once a HbAS erythrocyte gets infected with P. falciparum parasite. This alteration modulates cytoadherence and/or binding of the sickled erythrocytes to the peripheral blood mononuclear cells (PBMCs). Both cytoadherence and binding to PBMCs are responsible for the pathogenesis of malaria. Therefore, subjects of the HbAS genotype experience mild symptoms of malaria. The hypothesis could be tested in vitro by comparing the binding of P. falciparum infected HbAS and HbAA erythrocytes to platelet-endothelial cell adhesion molecule-1 (CD31) and by comparing the levels of tumor necrosis factor (TNF) and interferon gamma (IFN-gamma) following in vitro stimulation of PBMCs by HbAS and HbAA infected erythrocytes.

Sickle cell trait carriage: imbalanced distribution of IgG subclass antibodies reactive to Plasmodium falciparum family-specific MSP2 peptides in serum samples from Gabonese children.

Several mechanisms have been proposed for explaining the protection of young children with hemoglobin AS from severe Plasmodium falciparum malaria. In a previous study carried out in Gabon, we have shown an association between hemoglobin AS carriage and a greater P. falciparum infection complexity. In the present study, we have investigated the presence and fine specificity of merozoite surface protein 2 (MSP2) reactive antibodies using different peptides covering conserved and polymorphic regions (Blocks 1-3) of P. falciparum MSP2 molecules. A cross-sectional study was conducted in the city of Bakoumba (Gabon), where malaria is hyperendemic with perennial P. falciparum transmission. Among the 641 children included, 135 were heterozygous for the sickle cell trait (HbAS). There was no significant difference in age distribution (mean age: 5 years, 0.5-11 years) and sex ratio in both hemoglobin groups (HbAA vs. HbAS). Blood group O was, however, associated with the sickle cell trait (P=0.02). P. falciparum isolates obtained from children with HbAS had a trend to higher infection complexity before the age of 5 years. Plasma samples were tested for the presence of antibodies to the different MSP2 peptides. Total IgG antibodies with a predominant reactivity against the FC27 type (the predominant P. falciparum MSP2 genotype) were found in serum samples from both groups. The profile of the IgG subclasses varied according to the hemoglobin phenotype. IgG3 and IgG2 were predominantly detected in plasma samples from HbAS children, whereas mainly IgG3 was found in children with HbAA. The role of the high multiclonal carriage associated with high family-specific antibodies reactive to MSP2 in HbAS children with asymptomatic P. falciparum parasitism is discussed.

Platelet and leucocyte activation in childhood sickle cell disease: association with nocturnal hypoxaemia.

We hypothesized that vaso-occlusive events in childhood sickle cell disease (SCD) may relate to inflammatory cell activation as well as interactions between sickle erythrocytes and vascular endothelium. Peripheral blood was examined from 24 children with SCD, of whom 12 had neurological sequelae and seven had frequent painful crises, and 10 control subjects. Platelet (CD62P and CD40L expression) and granulocyte (CD11b expression) activation and levels of platelet-erythrocyte and platelet-granulocyte complexes were determined by flow cytometry. Platelets (P = 0.019), neutrophils (P = 0.02) and monocytes (P = 0.001) were more activated and there were increased platelet-erythrocyte complexes (P = 0.026) in SCD patients compared with controls. Platelet-granulocyte complexes were not raised. There were no differences between the different groups of SCD. As hypoxia activates monocytes, platelets and endothelial cells and causes sickling of SCD erythrocytes, we also investigated 20 SCD patients with overnight pulse oximetry. Minimum overnight saturation correlated with the level of platelet-erythrocyte complexes (Spearman's rho -0.668, P < 0.02), neutrophil CD11b (Spearman's rho -0.466, P = 0.038) and monocyte CD11b (Spearman's rho -0.652, P = 0. 002). These findings provide important clues about the mechanism by which SCD patients may become predisposed to vaso-occlusive events.

Elevated serum and bronchoalveolar lavage fluid levels of interleukin 8 and granulocyte colony-stimulating factor associated with the acute chest syndrome in patients with sickle cell disease.

The role of cytokines in the development of acute chest syndrome (ACS) in patients with sickle cell disease (SCD) was studied. Serum interleukin 8 (IL-8) levels were elevated in 14 episodes and undetectable in six out of 20 episodes of ACS in 19 patients with SCD. In contrast, IL-8 levels were undetectable in the sera of 29 control patients with SCD studied during routine clinic visits or hospitalization for vaso-occlusive crises. The differences in mean IL-8 levels and the proportion of patients with detectable levels between the two groups were highly significant (P < 0.0001 and 0.04 respectively). The mean IL-8 level in bronchial fluid samples from children with ACS was also significantly higher than that in sickle cell patients undergoing elective surgery (5500 +/- 1400 pg/ml vs. 1900 +/- 470 pg/ml, P = 0.03). Granulocyte colony-stimulating factor (G-CSF) (2000 +/- 1700 pg/ml) was present in five out of six samples of bronchial fluid, but not serum, from children with ACS. All but one of the patients with ACS studied were negative for the Duffy red cell antigen, which is a receptor that binds and inactivates IL-8 and other chemokines. These findings suggest that IL-8 and G-CSF may play a role in the development of the ACS and the complications associated with it.