D1.210 - Effects of Omalizumab on Human Basophils in Children with Cow’s Milk Protein Allergy

Omalizumab (OMA) is used for allergic treatment by reducing number of IgE on the cell surfaces of basophils and leading to lower expression of FcεRI on basophils. We aimed to investigate the effects of OMA treatment on human basophils.

Eighteen patients with IgE-mediated cow’s milk protein allergy (CMPA) were included. Of the 18 patients, 14 were on OMA treatment, four were not. To observe basophil activation, Basophil Activation Test (BAT) was performed in patients receiving OMA and not receiving OMA by using anti-FcεRI, fMLP and casein allergen. Immunological outcomes consisted of measuring CD63 expression on basophils using flow cytometry.

Among the 18 children, 12 were male with a median age of 9.5 years (interquartile range-IQR 4.2-12.9).  Median (IQR) total IgE, milk and casein sIgE levels were 832 (168-1615) IU/L, 80 (11.6-100) kU/L and 77 (6-100) kU/L, respectively. Total IgE showed positive correlation with anti-FcεRI activation (p=0.002), 100 ng/ml casein (p<0.001) and 1000 ng casein (p=0,004) in OMA negative group.  Anti-FcεRI activation showed positive correlation with 100 ng/ml casein (p<0.001) and 1000 ng casein (p<0.001) in OMA negative group but not in OMA positive group. Anti-FcεRI induced CD63 expression was significantly higher in OMA positive group [81.5 (72.0-89.0)] than OMA negative group [22.4 (12.8-67.8)] (p=0.026). We observed the same trend of higher activation of basophils with anti-FcεRI stimulation in the OMA receiving than OMA not receiving in 8 children who underwent Milk Oral immunotherapy.

Our results show that FcεRI mediated activation determined by CD63 expression was higher in OMA-treated group compared to OMA negative group. It shows OMA might enhance FcεRI dependent activation rather than suppress it.