Cytokine Production upon House Dust Mite Stimulation of Cord Blood Mononuclear Cells from Caesarean Section-Delivered Singaporean Infants

Background: Epidemiological data from cohort studies indicate associations between Caesarean section and development of allergy in infants. Besides the delayed colonization of commensal bacteria (which in turn affect the immune system development), the cytokine profile in C-section delivered infants could be different, which may be implicated in infant’s immunity.   

Methods: A clinical study was conducted at KK Women’s and Children’s Hospital, where 55 cord blood samples from Caesarean section-delivered infants were collected   to evaluate the response to allergens in the cord blood cells. Freshly isolated cord-blood mononuclear cells (CBMCs) were cultured in a 96-well plate at 100,000 cells per well (in triplicate per condition) and stimulated with the extracts from either one of major house dust mite species: Blomia tropicalis (BloT) and Dermatophagoides pteronyssinus (DerP). Phytohemagglutinin (PHA) and Lipopolysaccharide (LPS) were used as positive controls. The supernatants of these cutures were harvested after 5-day stimulation and were analyzed using the Bio-Plex Pro^TM Human Cytokine assay. The production of IL-5, IL-13, IFN-gamma and TNF-alpha by the allergen-stimulated CBMCs were analyzed.

Results: DerP stimulation induced a higher response as compared to BloT stimulation.  Following DerP stimulation, the median value of IL-5 was 2.5 pg/mL (0-172 pg/mL), IL-13 – 9.1 pg/mL (0-158 pg/mL), IFN-gamma - 321 pg/mL (69-1978 pg/mL) and TNF-alpha - 1393 pg/mL (74-5658 pg/mL). Among the 55 analysed subjects, while 3 subjects (5%) showed higher expression of IFN-gamma (above 1000 pg/mL) and lower expressions of IL-5 and IL-13 (both below 20 pg/mL), 6 subjects (11%) displayed higher expressions of IL-5 and IL-13 (both above 20 pg/mL). TNF-alpha levels were detected high in most subjects. Of note, no correlation between strong production of T_H2-like cytokines (IL-5 and IL-13) and parental allergy history was observed.

Conclusion: We observed a strong production of T_H2-like cytokines in 11% of C-section-delivered infants upon DerP stimulation. Interestingly, these infants did not have any history of parental allergy. This finding might indicate in utero sensitization of these infants. The TH2-like cytokine profile in cord blood might be useful as an early sign of atopic manifestations in future. We plan to follow-up these subjects in order to monitor the development of allergic response later in life.