Cyclic AMP-phosphodiesterase activity and histamine release in cord blood leukocyte preparations

Atopic dermatitis, allergic rhinitis and asthma are a common group of diseases with a familial predisposition. At present there is no suitable predictive or diagnostic marker. Adults with atopic dermatitis or allergic respiratory disease have elevated mononuclear leukocyte cAMP-phosphodiesterase activity. This activity correlates closely with histamine release from basophils. We investigated newborn leukocyte phosphodiesterase activity and histamine release in umbilical cord blood. Phosphodiesterase activity was significantly elevated in cord blood leukocytes of 81 children with a positive history of atopy in first degree relatives, compared to 33 children with a negative history (p less than 0.025). In contrast to adults there was no correlation between phosphodiesterase activity and histamine release. Our studies suggest that elevated phosphodiesterase activity is a primary, genetically linked defect. Fetal basophils would appear to possess cytophilic IgE since they are capable of immunologically stimulated histamine release even without passive, in vitro IgE sensitization. In addition, there are functional differences between adult and cord blood basophils. Longitudinal studies may determine if elevated phosphodiesterase is predictive of atopic states.

Basophil histamine release in atopic dermatitis and its relationship to disordered cyclic nucleotide metabolism

Maximal histamine release (HR) from leucocytes, in response to Concanavalin A (Con A) was significantly higher in a group of 16 adults with moderate to severe atopic dermatitis (AD) when compared to 13 non-atopic adults. In a further 4 adults with AD, HR was similar to that in the normals, suggesting the existence of 'high releaser' and 'low releaser' subsets within the AD group. Leucocyte cyclic AMP phosphodiesterase (PDE) activity was significantly higher in the 'high releaser' group compared to the 'low releaser' and normal groups. High and low HR responses showed strong correlations with high and low PDE. Pre-treatment of leucocytes from 'high releasers' with the experimental PDE PDE inhibitor RO-20-1724 reduced the HR to normal levels. These findings suggest that increased histamine 'releasability' in AD is related to abnormalities in cyclic nucleotide regulation. No significant HR could be demonstrated in response to a range of concentrations of methacholine in 'high releaser' atopics and normals. Methacholine also did not affect HR in response to maximal Con A stimulation in 'high releaser' atopics. Basophil percentages within the leucocyte preparation and the histamine content per basophil, were not significantly different between the atopics and normals. Con A-stimulated histamine release did not correlate significantly with serum IgE levels.