Concentrations of Immunoglobulin A, Interleukin-6, and Tumor Necrosis Factor in Breastmilk of Adolescent and Adult Mothers in Quito, Ecuador: A Cohort Study Nancy Flores, 1 Esteffania Villegas, 2 Daniela Villacı ´s, 2 Marco Fornasini, 1 Sara G. Cifuentes, 1 Luis Narva ´ ez, 1 and Manuel E. Baldeo ´n 1 Dear Editor: B reastmilk composition can be affected by maternal health, nutritional status, stress, and infant gestational age. 1 Another variable that may modify the immune compo- sition of breastmilk is the age of the mother, particularly as it relates to the relative developmental immaturity of the mam- mary gland in young mothers. Human mammary gland de- velopment is a complex process that has been divided into embryonic, adolescent, and adult phases, which are strictly regulated. 2 As the mammary alveolar epithelium is an important producer of the cytokines interleukin-6 (IL-6) and tumor necrosis factor (TNF) and is instrumental in immuno- globulin A (IgA) transport and secretion, its developmental differentiation state may affect the levels of these immune components in milk. 3 There is limited information on the im- mune components of breastmilk and how their abundance is regulated, and this is particularly true for the composition of breastmilk from adolescent mothers. The present study com- pares IgA2, IL-6, and TNF levels in breastmilk in colostrum, transition milk, and mature milk of adolescent and adult mothers attending the main obstetric center in Quito, Ecuador. Thirty-nine adolescent (16 – 1 years old) and 26 adult (20 – 4 years old) healthy primiparous volunteers were invited to par- ticipate during a period of 4 months. All mothers were recruited within the first 5 days postpartum. Inclusion criteria for volun- teers were as follows: nonsmokers, residence in the Quito met- ropolitan area, normal singleton pregnancy and vaginal delivery of the child, at-term parturition, and maternal willingness to exclusively breastfeed the child for the duration of the study. Colostrum, transition milk, and mature milk were obtained in the morning after an overnight fasting period of 8–10 hours. Concentrations of IL-6 and TNF were measured by chemilu- minescence, and IgA2 levels were assessed by immuno- turbidimetry. To establish differences within and between groups, paired Wilcoxon signed ranks test and the Mann– Whitney U test were used. Three important immune components were chosen to compare breastmilk from adolescent and adult mothers: IgA, the most important mucosal antibody protecting against in- fection, and two immune-modulatory cytokines, IL-6 and TNF. IgA levels were found to be highest in colostrum in both adolescent and adult mothers, with similar levels recorded in both groups (Table 1). Levels of the cytokines IL-6 and TNF were also highest in colostrum and decreased sequentially in transition and mature milk (Table 1). Although the overall trend of production of these immune components was similar between the two groups of mothers, adolescent mothers showed a significantly higher TNF levels in transition milk and mature milk compared with adult mothers (Table 1). Taken together, these data indicate that breastmilk undergoes notable changes in immune component levels as lactation progresses and that adolescent mothers secrete more TNF in their milk during the majority of the lactation period. To our knowledge, this is the first study to specifically ad- dress levels of IgA2, IL-6, and TNF in the milk of adolescent mothers and to compare them with adult mothers in the same population. In order to maximize the power to discern differ- ences in our small study population, we applied strict inclusion and exclusion criteria to carefully control for possible demo- graphic and health factors that could influence results and ap- plied a consistent milk collection protocol for all mothers. By comparing a homogeneous population of women differing only in their age, this study suggests that healthy mothers who un- dergo a normal pregnancy and vaginal birth for their first child show an important difference in the TNF levels in their breast- milk when they are under 19 years of age. Potential limitations of the present work include the limited number of subjects in- cluded in the study as well as the use of one sample from co- lostrum, transition, and mature milk. The difficulty in obtaining milk samples and the cost of the analysis precluded us from carrying out a more ample analysis. However, the reproduc- ibility of the data and similar trends in the studied groups show representative differences within and between groups. In conclusion, there are important differences in breastmilk composition between adolescent and adult breastfeeding mothers. Our work supports the idea that the young age of teen mothers affects the immune composition of breastmilk. We 1 Center of Translational Research, Faculty of Medicine, University of the Americas, Quito, Ecuador. 2 College of Health Sciences, San Francisco de Quito University, Quito, Ecuador. BREASTFEEDING MEDICINE Volume 9, Number 2, 2014 ª Mary Ann Liebert, Inc. DOI: 10.1089/bfm.2013.0085 107