We report a case of a very fast and intriguing decrease in IgE concentrations after exclusion from the diet of any CM lysate in an unusual clinical presentation of cow's milk allergy in an infant. Analysis of IgE kinetics after allergen elimination suggests rapid cessation of IgE biosynthesis and a short IgE half-life.
An unusual clinical presentation of cow's milk allergy (CMA) in an infant gave us the opportunity to observe a very fast and intriguing decrease of IgE concentrations after allergen withdrawal, raising new questions about IgE production and metabolism in newborns and infants.
A 17-day-old neonate, born to atopic parents at full term, was hospitalized in the children hospital of Tours (France) for poor feeding and increasing diarrhoea for 4 days, associated with a severe metabolic acidosis, after a symptom-free interval of 2 weeks. The diarrhoea ceased soon after admission. Erythema and a pustular rash of the face as well as a “gloves and socks-” type skin rash were noted at 18 days of age, leading to the finding of very high concentrations of total IgE (1298 kIU/L) and IgE specific to cow’s milk (CM) (83 kAU/L, Phadia) (Figure
Evolution of total IgE (●) and CM-specific IgE (■). IgE levels were measured on D19, D26, and D31. Predicted IgE kinetics are indicated as a black bold line. Extrapolated IgE kinetics are shown as grey lines (median in bold, 5 and 95% CI as normal lines). With only two values available, calculations were not performed for specific IgE.
The IgE detected in the newborn had been self-produced since IgE did not cross the placenta and his mother had no CM-specific IgE (not shown). This IgE immune response thus probably reflected a rapid maturation of IgE+ B cells into plasmablasts, as recently evidenced in mice [
Pharmacokinetic modelling techniques were used to describe the elimination kinetics of total IgE in this infant. The kinetics model was
Nevertheless, our findings suggest that the IgE production stopped rapidly—if not immediately—after allergen elimination, suggesting that a very limited IgE plasmablast life span combined with the very short IgE half-life. Whether this hypothetical IgE plasmablast short life span is restricted to IgE or whether it is due a more general immaturity of lymphoid niches in the newborn, as suggested in murine models [