LACK OF INCREASED NUMBERS OF LOW-DENSITY EOSINOPHILS IN THE CIRCULATION OF ASTHMATIC INDIVIDUALS

The density distribution pattern of eosinophils over discontinuous iso tonic Percoll gradients from the blood of normal, asymptomatic allergi c and non-allergic asthmatic individuals was investigated. There was a completely identical distribution pattern between the investigated gr oups. Analysis of the expression of surface markers for complement rec eptors CR1 and CR3 and immunoglobulin G receptor on eosinophils derive d from the density bands 1.080, 1-085 and 1.090 g/ml supported this fi nding since they did not reveal differences in expression between the bands within one group but also not between the three groups. Eosinoph ils of the various density bands were further purified and stimulated in vitro to produce leukotriene C4 (LTC4) by the calcium ionophore A23 187 or serum treated zymosan. Equal amounts of LTC4 were synthesized b y the eosinophils of the various density bands within one group. Howev er, it appeared that the eosinophils of all density bands of allergic and non-allergic asthmatics synthesized significantly more LTC4 than t he eosinophils from normal individuals (five-to tenfold). Probably thi s indicates in vivo priming of the eosinophils in asthmatic individual s which is not reflected by a change in density. Control experiments, dealing with possible artifacts due to the isolation procedure or the patient selection, to find differences in distribution patterns over d iscontinuous Percoll density gradients of the eosinophils of asthmatic compared to normal individuals failed to show such a difference. Ther efore, the density distribution pattern of eosinophils over these grad ients does not reflect cell activation, whereas LTC4 formation clearly does. This could mean that LTC4 formation is a more sensitive paramet er for cell activation than density distribution or cell surface marke r expression.