Published Online: October 29, 2015
Several immune-mediated diseases like asthma, rheumatoid arthritis, and multiple sclerosis have birth season as a common risk factor, although the critical season varies depending on the disease. This phenomenon could link to imprinting of neonatal immune function, as it seems to be more strongly associated to birth season than to other independent birth variables such as gender, birth weight and cesarean delivery. Still it is unclear how birth season could program and influence the immune phenotype at birth.
In a study recently published in The Journal of Allergy and Clinical Immunology (JACI), Thysen and colleagues related season of birth to a detailed characterization of 26 cell types in cord blood as well as in situ production of 20 cytokines in the upper airways at one month of age. All 570 participating children were part of the Copenhagen Prospective Studies on Asthma in Childhood 2010 (COPSAC2010) birth cohort of 700 unselected mothers.
The authors found that neonatal immune function fluctuated by birth season. Specifically, winter birth was associated with higher levels of most cell types and cytokines, while this was opposite for summer births, where cell and cytokine levels were generally lowest. Fall birth was mainly represented with a type 2 immune profile represented by higher IL-13 and eosinophils, but also recent immune activation. Spring birth showed high levels of type 2 chemokine levels. The birth seasonal fluctuation of the airway immune cytokines was independent of simultaneous presence of bacteria and virus in the upper airways.
These results show that birth season fluctuations seem to affect neonatal immune development and result in differential potentiation of cord blood immune cells and early airway mucosa immune function. The observed seasonal-linked immune profiles were similar to the known immune pathology of type 2 immune-mediated diseases associated with fall and winter birth. It is speculated that the immune deviation may affect the child’s ability to handle microbial exposure in early life.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.