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1 (2004) 58, & 2004 Nature Publishing Group All rights reserved /04 $ ORIGINAL COMMUNICATION Relationship of vitamin A deficiency, iron deficiency, and inflammation to anemia among preschool children in the Republic of the Marshall Islands MV Gamble 1, NA Palafox 2, B Dancheck 3, MO Ricks 3, K Briand 4 and RD Semba 3 * 1 Department of Environmental Health Sciences, Columbia University Mailman School of Public Health, New York, NY, USA; 2 Department of Family Practice and Community Health, John A Burns School of Medicine, University of Hawaii, Honolulu, HI, USA; 3 Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; and 4 Ministry of Health and Environment, Republic of the Marshall Islands Introduction: Although vitamin A deficiency, iron deficiency, and inflammation may contribute to anemia, their relative contribution to anemia has not been well characterized in preschool children in developing countries. Objective: To characterize the contributions of vitamin A and iron deficiencies and inflammation to anemia among preschool children in the Republic of the Marshall Islands. Subjects and methods: A community-based survey, the Republic of the Marshall Islands Vitamin A Deficiency Study, was conducted among 919 preschool children. The relationship of vitamin A and iron status and markers of inflammation, tumor necrosis factor-a, a 1 -acid glycoprotein, and interleukin-10, to anemia were studied in a subsample of 367 children. Results: Among the 367 children, the prevalence of anemia was 42.5%. The prevalence of severe vitamin A deficiency (serum vitamin A o0.35 mmol/l) and iron deficiency (serum ferritin o12 mg/dl) were 10.9 and 51.7%, respectively. The respective prevalence of iron deficiency anemia (hemoglobin o110 g/l and iron deficiency), anemia with inflammation (anemia with TNFa42 pg/ml and/or AGP mg/l), and severe vitamin A deficiency combined with anemia was 26.7, 35.6, and 7.6%. In multivariate linear regression models that adjusted for age, sex, and inflammation, both iron deficiency (odds ratio (OR) 1.74, 95% confidence interval (CI) , P ¼ 0.023) and severe vitamin A deficiency (OR 4.85, 95% CI , Po0.0001) were significantly associated with anemia. Conclusions: Both iron and vitamin A deficiencies were independent risk factors for anemia, but inflammation was not a significant risk factor for anemia among these preschool children. (2004) 58, doi: /sj.ejcn Published online 31 March 2004 Keywords: anemia; ferritin; hemoglobin; inflammation; iron deficiency; retinol; vitamin A deficiency Introduction Anemia is a major problem among preschool children in developing countries worldwide. Iron deficiency, vitamin A deficiency, and inflammation may lead to anemia among children, but the relative contribution of these various factors has not been well characterized. Iron deficiency is the main cause of anemia in preschool children worldwide *Correspondence: RD Semba, 550 North Broadway, Suite 700, Baltimore, MD 21205, USA. rdsemba@jhmi.edu Guarantors: MV Gamble, RD Semba. Received 13 January 2003; revised 28 April 2003; accepted 22 May 2003; published online 31 March 2004 (Allen & Casterline-Sabel, 2001), and iron deficiency anemia has been associated with delayed psychomotor development and growth retardation (Lozoff & Wachs, 2001). Vitamin A deficiency may contribute to anemia through effects on iron metabolism, hematopoiesis, and increased susceptibility to infection (Semba & Bloem, 2002). Infectious diseases and inflammation are thought to cause anemia through suppression of erythropoiesis by proinflammatory cytokines such as tumor necrosis factor-a (TNF-a) (Means, 2000). TNF-a is produced by macrophages and appears to inhibit erythropoiesis (Murphy et al, 1988). Interleukin-10 (IL-10), an antiinflammatory cytokine, plays a role in T-helper 2-like immune responses (Othoro et al, 1999) and downregulates TNF-a expression, and in vitro studies suggest that IL-10 may

2 stimulate erythropoiesis (Wang et al, 1996). The ratio of IL-10 to TNF-a has been associated with the severity of anemia among children with malaria (Othoro et al, 1999), but it is unclear whether the ratio of IL-10 to TNF-a is associated with anemia among children without malaria. a 1 -Acid glycoprotein (AGP), an acute-phase protein produced by hepatocytes, has been shown to stimulate the production of TNF-a by human monocytes in vitro (Su et al, 1999). According to the World Health Organization, the estimated overall prevalence of anemia among preschool children in developing countries is 42% (ACC/SCN, 2000). Iron deficiency has usually been implicated as the main cause of anemia among preschool children. Vitamin A deficiency has been reported to cause anemia, but the epidemiology and pathogenesis of the anemia associated with vitamin A deficiency have not been well characterized (Semba & Bloem, 2002). Few studies of preschool children in developing countries have examined the relationship between anemia and vitamin A deficiency, iron deficiency, and inflammation in the same population. Recently, a high prevalence of vitamin A deficiency has been described among preschool children in the southern and western areas of the Pacific (Semba & Palafox, 2002), and a high prevalence of anemia has been described among preschool children in the Republic of the Marshall Islands (Flores, 1991). The prevalence of vitamin A deficiency and of anemia appears to be consistent with figures reported for many regions with developing countries worldwide (ACC/SCN, 2000). We hypothesized that iron deficiency, vitamin A deficiency, and inflammation were independent risk factors for anemia among preschool children in the Republic of the Marshall Islands. In order to test this hypothesis, we characterized iron status, vitamin A status, markers of inflammation and anemia in a cross-sectional study of Marshallese preschool children. Subjects and methods A community-based survey, known as the Republic of the Marshall Islands Vitamin A Deficiency Study, was conducted between September and November The total survey included 919 Marshallese children, ages 1 5 y, from 10 atolls, who represented approximately 20% of the entire population of 1 5-y-old children living in the Republic of the Marshall Islands (Gamble et al, 2001). The sampling strategy for the study was based on the 1988 census of the Republic of the Marshall Islands, which provided data on the average number of children of the target age group within each household, determined by dividing the number of children in a locality by the number of households in the same location. This number was then divided into the number of children to be sampled to obtain the number of households to be visited. Households to be visited were chosen by systematic sampling of every fifth household. When available, the date of birth of children was ascertained from the children s health cards, otherwise the date of birth was obtained by asking the parent or guardian. The survey team consisted of at least one Marshallese-speaking health care worker, a phlebotomist, and a medical doctor. Oral informed consent was obtained from a parent or guardian prior to participation in the survey as considered appropriate by the institutional review board for this setting. The Ministry of Health and Environment of the Republic of the Marshall Islands supported the project and assisted with the planning and development of this evaluation. A population census was repeated again in 1999 in the Marshall Islands. Blood samples were obtained by venipuncture. Hemoglobin was measured using a HemoCue instrument (HemoCue Inc, Mission Viejo, CA, USA). Venous blood samples were immediately wrapped in aluminum foil and stored at 41C until centrifugation (200 g, 10 min, room temperature) in a local laboratory. Aliquots of serum were made in cryovials, and samples were placed immediately in liquid nitrogen. Serum samples were kept in liquid nitrogen or at 701C until the time of laboratory analyses during Serum retinol was measured using reversed-phase high-performance liquid chromatography as described elsewhere (Gamble et al, 2001). Serum retinol and hemoglobin were measured in 919 and 904 children, respectively. The present study of anemia, iron deficiency, vitamin A deficiency, and inflammation was conducted with a subsample involving the first 367 of the 919 children enrolled in the study. Enzyme-linked immunosorbent assay was used to measure ferritin (Human Ferritin Enzyme Immunoassay Test Kit, American Laboratory Products Company, Windham, NH, USA), TNF-a (Human TNF-a, Quantikine High Sensitivity, R & D Systems, Minneapolis, MN, USA), and IL-10 (Human IL- 10, BD Pharmingen, San Diego, CA, USA). Radial immunodiffusion assay was used to measure AGP (Bindarid, The Binding Site, Birmingham, UK). The within- and betweenassay coefficients of variation (CV) for retinol, ferritin, TNFa, IL-10, and AGP, were 3 and 8%, 3 and 9%, 4 and 9%, 4 and 5%, and 5 and 2%, respectively. Within- and between-assay CV were not obtained for hemoglobin measurements using the HemoCue. Pooled human standards were used to measure intra- and interassay CVs in laboratory analyses. The study protocol was approved by institutional review board of the Pacific Health Research Institute of Hawaii and the Ministry of Health and Environment of the Republic of the Marshall Islands. Groups were compared using Student s t-test or analysis of variance for continuous variables where appropriate, and categorical variables were compared using w 2 or exact tests. Variable transformations were made where necessary to achieve a normal distribution. Anemia was defined as hemoglobin o110 g/l (WHO/UNICEF/UNU, 1997). Vitamin A deficiency was defined as serum retinol o0.35 mmol/l (West & Darnton-Hill, 2001), and vitamin A deficiency anemia was defined as serum retinol o0.35 mmol/l and hemoglobin o110 g/l. Iron deficiency was defined as serum ferritin o12 mg/l, and iron deficiency anemia was defined as 1397

3 1398 ferritin o12 mg/l and hemoglobin o110 g/l (WHO/UNICEF/ UNU, 1997). Inflammation was defined as TNF-a42 pg/ml and/or AGP mg/l. The IL-10 to TNF-a ratio was calculated as IL-10 in pg/ml divided by TNF-a in pg/ml. In the statistical analyses, for children who had undetectable TNF-a, AGP, or IL-10, the values were assigned to the lower limit of detection of these commercial assays, that is, 2 pg/ ml, 190 mg/l, or 3.9 pg/ml, respectively. Univariate and multivariate logistic regression models were used to estimate the relative risks of factors associated with anemia. Regression coefficients were converted to odds ratios (OR), and confidence intervals (CI) for the OR were derived from the standard error estimates of the regression coefficients. Results There were 367 children who had hemoglobin, retinol, ferritin, and TNF-a measured of the 919 children in the survey. Owing to limited sample volume, of the 367 children, serum AGP and IL-10 were not measured in 89 and 105 children, respectively. The mean age (7s.d.) of the 367 children was y, and there were 184 boys and 183 girls. The subsample of children involved in the present study was compared by age and sex with the children who were not selected for the study, and there were no significant differences by age, sex, retinol, or hemoglobin concentrations (data not shown). Of the 367 children, there were 156 children, or 42.5%, who were anemic. There were 40 children, or 10.9%, who had severe vitamin A deficiency (serum retinol o0.35 mmol/ l), and 28 children, or 7.6%, who had severe vitamin A deficiency combined with anemia. There were 190 children, or 51.7%, who had iron deficiency (serum ferritin o12 mg/l), and 98 children, or 26.7%, who had iron deficiency anemia. A total of 23 children, or 6.2%, had both severe vitamin A deficiency and iron deficiency, and a total of 17 children, or 4.6%, had both severe vitamin A deficiency, iron deficiency, and anemia. Among children with or without both iron deficiency and severe vitamin A deficiency, the mean hemoglobin concentrations (7s.d.) were and mg/l (Po0.0001), respectively. There were 117 children (35.6%) who had anemia and inflammation (elevated TNF-a and/or AGP), which was considered in this study to be consistent with the anemia of chronic disease. The mean age (7s.d.) of children with and without anemia with inflammation was and y (Po ), respectively. The proportion of boys and girls with anemia and inflammation was 35.7 and 35.6% (P ¼ 0.97), respectively. The relationship between serum retinol concentrations, iron deficiency, inflammation, and anemia is presented in Table 1. Serum retinol concentrations were stratified as o0.35, 0.35 o0.70, and Z0.70 mmol/l, as per convention. Children with serum retinol concentrations Z0.70 mmol/l were significantly younger than those with lower serum retinol concentrations, but there were no significant differences across vitamin A category by sex. Both mean hemoglobin and the prevalence of anemia was significantly different across vitamin A category, with a higher prevalence of anemia found among children with serum retinol concentrations o0.35 mmol/l. The proportion of children with the anemia with inflammation was significantly higher among children who had low serum retinol concentrations. Mean log 10 AGP was higher among children who had lower serum retinol concentrations. There were no significant differences in log 10 TNF-a, log 10 IL-10, or log 10 IL-10/TNF-a ratio across serum retinol categories. The relationship between iron status, as reflected by serum ferritin concentrations o12 or Z12 mg/l, and inflammation is shown in Table 2. Children with low serum ferritin (o12 mg/l) were significantly younger than children with Table 1 Relationship between serum vitamin A concentrations and hemoglobin and inflammation among preschool children Serum retinol (mmol/l) Characteristic a o to o0.70 Z0.70 P Age (y) [40] [201] [126] Sex (% girls) 42.5 [40] 50.2 [201] 51.6 [126] 0.39 Hemoglobin (mg/l) [40] [201] [126] Anemic (%) b 70.0 [40] 38.8 [201] 39.6 [126] Iron deficiency anemia (IDA) (%) c 42.5 [40] 24.4 [201] 25.4 [126] 0.13 Anemia with inflammation (%) d 66.6 [36] 32.2 [180] 31.2 [112] Log 10 tumor necrosis factor-a (TNF-a) (pg/ml) [40] [200] [126] 0.56 TNF-a 42 pg/ml (%) 52.5 [40] 56.2 [200] 51.6 [126] 0.66 Log 10 interleukin-10 (IL-10) (pg/ml) [30] [147] [85] 0.3 Log 10 IL-10/TNF-a ratio [30] [147] [85] 0.85 Log 10 a 1 -acid glycoprotein (AGP) (mg/l) [32] [157] [89] AGP mg/l (%) 68.7 [32] 57.9 [157] 49.4 [89] a For continuous variables, mean7s.d. Number shown in brackets. Comparison of continuous variables by ANOVA. b Defined as hemoglobin o110 g/l. c Defined as hemoglobin o110 g/l and ferritin o12 mg/l. d Defined as hemoglobin o110 g/l and TNF-a 42 pg/ml and/or AGP41000 mg/l.

4 Table 2 Relationship between iron status and hemoglobin and inflammation among preschool children Serum ferritin (mg/l) 1399 Characteristic a o12 Z12 P Age (y) [190] [177] Sex (% girls) 51.5 [190] 48.0 [177] 0.49 Hemoglobin (mg/l) [190] [177] Anemic (%) b 51.6 [190] 32.7 [177] Anemia with inflammation (%) 43.1 [167] 27.9 [161] Log 10 TNF-a (pg/ml) [190] [177] 0.58 TNF-a 42 pg/ml (%) 52.6 [190] 55.9 [177] 0.52 Log 10 IL-10 (pg/ml) [131] [131] 0.05 Log 10 IL-10/TNF-a ratio [131] [131] Log 10 AGP (mg/l) [138] [140] 0.55 AGP41000 mg/l (%) 55.8 [138] 57.1 [140] 0.82 a For continuous variables, mean7s.d. Number shown in brackets. b Defined as hemoglobin o110 g/l. Table 3 Severe vitamin A deficiency and iron deficiency as risk factors for anemia Risk factor Univariate OR (95% CI) P Multivariate OR. (95% CI) P Age (/y) 0.63 ( ) ( ) Male sex 1.03 ( ) ( ) 0.40 Vitamin A deficiency a 3.62 ( ) ( ) Iron deficiency b 2.18 ( ) ( ) Inflammation c 1.12 ( ) ( ) 0.86 a Defined as serum vitamin A o0.35 mmol/l. b Defined as serum ferritin o12 mg/l. c Defined as TNF-a 42 pg/ml and/or AGP mg/l. higher serum ferritin (Z12 mg/l). Lower serum ferritin was associated with lower mean hemoglobin and a higher proportion of anemia. There were no significant differences in log 10 TNF-a between the two categories of serum ferritin concentrations. Log 10 IL-10 was significantly higher among children with low serum ferritin compared with higher serum ferritin. The proportion of children with anemia and inflammation was significantly higher among children with iron deficiency than children without iron deficiency. The log 10 IL-10/TNF-a ratio appeared to be higher among children with low serum ferritin, but the results did not reach significance (P ¼ 0.089). Univariate and multivariate logistic regression models were used to examine the relationship between age, male sex, severe vitamin A deficiency, iron deficiency, and inflammation with anemia (Table 3). In univariate models, only severe vitamin A deficiency and iron deficiency were significantly associated with anemia. In a final multivariate model that adjusted for age, sex, and inflammation, both severe vitamin A deficiency and iron deficiency were independent risk factors for anemia. Discussion These data suggest that both severe vitamin A deficiency and iron deficiency are independent risk factors for anemia among preschool children in the Marshall Islands. To our knowledge, this is the first study to characterize the association of vitamin A deficiency, iron deficiency, and inflammation with anemia among preschool children. Severe vitamin A deficiency was independently associated with anemia among preschool children, both in univariate models and in multivariate models that adjusted for iron deficiency, sex, age, and inflammation. Iron deficiency is a major cause of anemia among preschool children (Allen & Casterline-Sabel, 2001), and as would be expected, iron deficiency was also independently associated with increased risk of anemia. A limitation of this study is that these data were conducted in 1994 and some of the laboratory analyses were conducted later. The situation of subclinical vitamin A deficiency, iron deficiency, and inflammation is a basic one in many developing countries, and the purpose of this study was to examine the relationships between vitamin A deficiency, iron deficiency, inflammation, and anemia. Contrary to one of our hypotheses, inflammation, as reflected by elevated serum TNF-a and/or elevated AGP, was not significantly associated with anemia in either univariate or multivariate analyses. One potential explanation is that the children in this study were drawn from a communitybased survey and were relatively healthy compared with clinic- and hospital-based studies. A stronger association between elevated TNF-a and/or elevated AGP and anemia

5 1400 might be found among ill children drawn from a clinic or hospital-based study, where the anemia of chronic disease would be more common. Elevations of serum TNF-a and/or AGP can occur in the presence of infection, such as malaria (Nussenblatt et al, 2001), diarrheal disease (Azim et al, 1999), or acute lower respiratory infection (Wang et al, 1999). This study was limited in that other acute-phase response proteins, such as C-reactive protein, were not measured, and it is possible that a combination of elevated AGP and/or elevated C-reactive protein would have detected a greater proportion of children with inflammation than AGP alone. Two other limitations of the study is that blood smears for malaria and stool assays for detection of hookworm were not conducted in these children and anthropometry was not conducted on all the children in the survey. Children with ferritin o12 mg/l had significantly higher mean concentrations of IL-10 than children with ferritin Z12 mg/l. The precise role of IL-10 in the pathogenesis of anemia is unclear, but administration of IL-10 to humans has been shown to worsen anemia and increase circulating ferritin concentrations (Tilg et al, 2002). Thus, elevated IL-10 has been hypothesized to contribute to iron restriction to erythroid progenitor cells (Tilg et al, 2002). However, in contrast, IL-10 has been shown to downregulate the expression of TNF-a by human monocytes (Wang et al, 1999), an effect that might be expected to inhibit the suppression of erythropoiesis by TNF-a. Among children with acute malaria, a high ratio of IL-10 to TNF-a is associated with milder anemia (Othoro et al, 1999; Nussenblatt et al, 2001). In contrast, with the present study, which did not involve children with malaria, children with iron deficiency seemed to have a higher IL-10/TNF-a ratio than children without iron deficiency. Further studies are needed to examine the potential roles of IL-10 and TNF-a in the pathogenesis of anemia in children. Vitamin A supplementation or fortification has been shown in controlled clinical trials to increase hemoglobin concentrations among preschool children in Indonesia (Muhilal et al, 1988), Guatemala (Mejía & Chew, 1988), and Tanzania (Mwanri et al, 2000), or improve indicators of iron status among preschool children in Indonesia (Semba et al, 1992) and Thailand (Bloem et al, 1990). Among pregnant women in Indonesia, 2.4 mg retinol equivalent of vitamin A per day increased hemoglobin concentrations (Suharno et al, 1993). Vitamin A supplementation combined with iron supplementation has been shown to have a larger effect on increasing hemoglobin concentrations than vitamin A alone (Mwanri et al, 2000; Suharno et al, 1993). Such additive effects of vitamin A to iron supplementation have been attributed to increased mobilization of hepatic stores of vitamin A (Semba & Bloem, 2002). The data from the present study are consistent with the idea that both vitamin A and iron deficiencies may contribute to the pathogenesis of anemia among preschool children and are consistent with evidence from controlled clinical trials. Further investigation is needed to characterize the relationship between vitamin A deficiency, iron deficiency, inflammation, and anemia in other populations of preschool children. In populations of preschool children with a high prevalence of vitamin A deficiency, clinical trials suggest that strategies aimed at both vitamin A and iron deficiencies may be more effective in reducing anemia than strategies aimed at either single micronutrient deficiency (Semba & Bloem, 2002). Acknowledgements We thank the health care workers in the Republic of the Marshall Islands, especially Laling Riklon, Grace Heine, Kenya Amles, and Ailon Moses, for their diligent assistance, and Dana Totin for her assistance in interpretation of the data. This study was supported in part by the Pacific Health Research Institute, UNICEF, the Fergussen Foundation Hawaii, the Hawaii Community Foundation, Ministry of Health and Environment, Republic of the Marshall Islands, the National Institute of Child Health and Human Development (HD30042), the National Institutes of Health, and the United States Agency for International Development (Cooperative Agreement HRN A ). References Administrative Committee on Coordination/Sub-Committee on Nutrition (ACC/SCN) (2000): Fourth Report on the World Nutrition Situation. Geneva: ACC/SCN. Allen L & Casterline-Sabel J (2001): Prevalence and causes of nutritional anemias. In Nutritional Anemias, ed. U Ramakrishnan, pp Boca Raton, FL: CRC Press. Azim T, Ahmad SM, Sefat-E-Khuda, Sarker MS, Unicomb LE, Soma D, Hamadani JD, Salam MA, Wahed MA & Albert MJ (1999): Immune response of children who develop persistent diarrhea following rotavirus infection. Clin. Diag. Lab. Immunol. 6, Bloem MW, Wedel M, van Agtmaal EJ, Speek AJ, Saowakontha S & Schreurs WHP (1990): Vitamin A intervention: short-term effects of a single, oral, massive dose on iron metabolism. Am. J. Clin. Nutr. 51, Flores EG (1991): Report of the National Nutrition Survey of the Republic of the Marshall Islands. New York: UNICEF. Gamble MV, Ramakrishnan R, Palafox NA, Briand K, Berglund L & Blaner WS (2001): Retinol binding protein as a surrogate measure for serum retinol: studies in vitamin A-deficient children from the Republic of the Marshall Islands. Am. J. Clin. Nutr. 73, Lozoff B & Wachs TD (2001): Functional correlates of nutritional anemias in infancy and early childhood child development and behavior. In Nutritional Anemias, ed. U Ramakrishnan, pp Boca Raton, FL: CRC Press. Means Jr RT (2000): The anaemia of infection. Ballière s Clin. Hematol. 13, Mejía LA & Chew F (1988): Hematological effect of supplementing anemic children with vitamin A alone and in combination with iron. Am. J. Clin. Nutr. 48, Muhilal, Permeisih D, Idjradinata YR, Muherdiyantiningsih & Karyadi D (1988): Vitamin A-fortified monosodium glutamate and health, growth, and survival of children: a controlled field trial. Am. J. Clin. Nutr. 48, Murphy M, Perussia B & Trinchieri G (1988): Effects of recombinant tumor necrosis factor, lymphotoxin, and immune interferon on

6 proliferation and differentiation of enriched hematopoietic precursor cells. Exp. Hematol. 16, Mwanri L, Worsley A, Ryan P & Masika J (2000): Supplemental vitamin A improves anemia and growth in anemic school children in Tanzania. J. Nutr. 130, Nussenblatt V, Mukasa G, Metzger A, Ndeezi G, Garrett E & Semba RD (2001): Anemia and interleukin-10, tumor necrosis factor alpha, and erythropoietin levels among children with acute, uncomplicated Plasmodium falciparum malaria. Clin. Diag. Lab. Immunol. 8, Othoro C, Lal AA, Nahlen B, Koech D, Orago ASS & Udhayakumar V (1999): A low interleukin-10 tumor necrosis factor-a ratio is associated with malaria anemia in children residing in a holoendemic malaria region in western Kenya. J. Infect. Dis. 179, Semba RD & Bloem MW (2002): The anemia of vitamin A deficiency: epidemiology and pathogenesis. Eur. J. Clin. Nutr. 56, Semba RD & Palafox NA (2002): Prevention of nutritional blindness in the South Pacific. Asia-Pacific J. Ophthalmol. 14, Semba RD, Muhilal, West Jr KP, Winget M, Natadisastra G, Scott A & Sommer A (1992): Impact of vitamin A supplementation on hematological indicators of iron metabolism and protein status in children. Nutr. Res. 12, Su SJ, Yang BC, Wang YW & Yeh TM (1999): Alpha 1-acid glycoprotein-induced tumor necrosis factor secretion of human monocytes is enhanced by serum binding proteins and depends upon protein tyrosine kinase activation. Immunopharmacology 41, Suharno D, West CE, Muhilal, Karyadi D & Hautvast GAJ (1993): Supplementation with vitamin A and iron for nutritional anaemia in pregnant women in West Java, Indonesia. Lancet 342, Tilg H, Ulmer H, Kaser A & Weiss G (2002): Role of IL-10 for induction of anemia during inflammation. J. Immunol. 169, Wang CQ, Udupa KB & Lipschitz DA (1996): Evidence suggesting a stimulatory role for interleukin-10 in erythropoiesis in vitro. J. Cell. Physiol. 166, Wang CM, Tang RB, Chung RL & Hwang BT (1999): Tumor necrosis factor-alpha and interleukin-6 profiles in children with pneumonia. J. Microbiol. Immunol. Infect. 32, West Jr KP & Darnton-Hill I (2001): Vitamin A deficiency. In Nutrition and health in developing countries, eds. RD Semba & MW Bloem, pp Totowa, NJ: Humana Press. WHO/UNICEF/UNU (1997): Iron Deficiency: Indicators for Assessment and Strategies for Prevention. Geneva, World Health Organization. 1401