Large number of CD19+/CD23+ B cells and small number of CD8+ T cells as early markers for cow's milk allergy (CMA).

Assessment of activation of immune mechanisms is valuable in the early diagnosis of cow's milk allergy (CMA). The purpose of this study was to evaluate peripheral blood lymphocyte subclasses in children suspected of having CMA and healthy infants in order to detect an early marker for food allergy. Altogether 47 breast-fed infants, aged from 0.4 to 10 months were followed-up prospectively from birth because of atopic heredity. Twenty-three of the infants were healthy and 24 infants had a strong suspicion of and later challenge-proven cow's milk allergy. Leucocyte subsets were determined from peripheral blood mononuclear cells by flow cytometry. In response to a clinical cow's milk challenge, seven infants developed urticaria, 11 infants had eczema, three patients had loose stools, diarrhoea or vomiting and three infants had eczema and diarrhoea, loose stools or vomiting. The total percentage of B cells and also the proportion of B cells bearing a low-affinity IgE receptor as a marker for activation were significantly higher, whereas the percentage of CD8+ T cells was significantly lower in infants with challenge-proven CMA than in healthy controls. These results imply that infants with active CMA have a defect in regulation of B-cell function. Further, they suggest that imbalance of the ratio of suppressor and helper T cells might be an important factor in the etiopathogenesis of CMA. Our results show that large numbers of activated CD19+ B cells and low numbers of CD8+ T cells could be considered as early markers for food allergy since they are already detectable in peripheral blood during the earliest symptoms of CMA.