Immune system development during early childhood in tropical Latin America: Evidence for the age-dependent down regulation of the innate immune response

Laboratorio de Investigaciones FEPIS, Quininde, Esmeraldas Province, Ecuador.
Clinical Immunology (Impact Factor: 3.67). 03/2011; 138(3):299-310. DOI: 10.1016/j.clim.2010.12.011
Source: PubMed


The immune response that develops in early childhood underlies the development of inflammatory diseases such as asthma and there are few data from tropical Latin America (LA). This study investigated the effects of age on the development of immunity during the first 5 years of life by comparing innate and adaptive immune responses in Ecuadorian children aged 6-9 months, 22-26 months, and 48-60 months. Percentages of naïve CD4+ T cells declined with age while those of memory CD4(+) and CD8(+) T cells increased indicating active development of the immune system throughout the first five years. Young infants had greater innate immune responses to TLR agonists compared to older children while regulatory responses including SEB-induced IL-10 and percentages of FoxP3(+) T-regulatory cells decreased with age. Enhanced innate immunity in early life may be important for host defense against pathogens but may increase the risk of immunopathology.

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Available from: Laura C Rodrigues
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    • "Evaluation of the effect of urban vs. rural environment on TLR-induced innate immune responses in infants in South America was the first to reveal striking influence of postnatal environment on innate immunity, with IFNγ and IL-10 production both significantly elevated in urban compared to rural infants (Teran et al., 2011). In European infants, TLR responses differ already at the age of 1 month according to environmental exposure during the first month of life, with concentrations of monocytes negatively associating with breastfeeding and siblings in the home, and positively associating with exposure to pets (Belderbos et al., 2011). "
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    • "However, the study by Burl et al. was cross-sectional in nature, and progressive changes in innate immunity over the first year of life could thus have been influenced by inter-individual variability [24]. A similar decline consistent with our findings and those of Burl et al. in TLR induced cytokine production in whole blood was also detected in children born and raised in Ecuador; this decline was observed between 1 and 2 years of age, with no information provided about the earlier time points [23]. However, such decline was not observed in a recent study of infants in Papa New Guinea [22]. "
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    • "Gridebacke et al. (33) and Fichizawa et al. (32) found increased expression of CD4+CD25+Foxp3+ Treg cells in the peripheral blood during the first few days of life, followed by stabilization in the level of Treg cells during the first years of life. Furthermore, Teran et al. (34) evaluated a group of children from Latin America and found a significant decrease in the relative amount of Treg cells as age increased. Furthermore, similar to our study, Teran et al. also found variability in the Treg levels in individuals of the same age, indicating that factors such as environment may affect the development of the regulatory arm of the immune system. "
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