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

Abstract

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.

Antigen-Specific Memory T Cell Responses after Vaccination with an Oral Killed Cholera Vaccine in Bangladeshi Children and Comparison to Responses in Patients with Naturally Acquired Cholera

“…As with the T FH subset, the absence of guthoming T EM cells in younger children receiving vaccine may in part explain differences in protective efficacy afforded by OCV in younger versus older children. The absence of significant memory T cell responses in younger children receiving vaccine may relate to the lower frequency of these cells during early childhood and the gradual increase in this cell population during the first 5 years of life (43,44). In studies of a novel tuberculosis vaccine, a lower frequency of cytokine-secreting CD4 ϩ T cells was also observed in younger children than was seen in adolescents (38).…”

Individual variation and longitudinal pattern of genome-wide DNA methylation from birth to the first two years of life

“…Data from our IPA indicate that many of the significant CpG sites are associated with genes that are known to be involved in the development and function of various systems including the immune system, which begins in utero and matures during the first few years of life. 39,40 Our study has the following merits. We have presented the first genome-wide DNA methylation profiles at birth and within the first two years of life in a prospective US birth cohort.…”

Development of monocyte Toll-like receptor 2 and Toll-like receptor 4 in preterm newborns during the first few months of life

“…For this reason, much attention has been paid recently to the postnatal development of TLRs. Some studies have investigated the changes in cytokine responses of monocytes to TLR agonists during the first year after birth (16)(17)(18)(19), whereas others have focused on the changes that occur in the few years after birth (2,16,20,21) in neonates. However, these studies were performed mainly, if not entirely, using data from full-term newborns.…”