Inactivation of heamolytic complement by house dust allergen in the serum of children with atopic diseases.

Purified house dust allergen has been employed for screening the susceptibility to inactivation of haemolytic complement in the blood serum of atopic children and control subjects. Fluid phase complement in the control group of children was more sensitive to allergen-induced inactivation than observed in a normal adult population. Though the mean complement sensitivity indices in all groups of patients were below the valve for the control group, there was considerable statistical overlap. The serum complement sensitivities were in no way related to the clinical manifestations. The results of the complement test were not correlated to the total IgE levels, the RAST scores nor the skin reactions with house dust allergen. Some evidence for the in vivo involvement of the complement system in childhood atopic allergy was provided: the mean C3 proactivator level was significantly lower in atopic children, than in the control group; the mean C4 level in children with bronchial asthma and in children with atopic dermatitis was significantly depressed. A significant positive correlation between the serum C4 levels and allergen-complement sensitivities in children with both bronchial asthma and atopic dermatitis was observed.