Allergic bronchial asthma: eosinophil chemotaxis and antihistaminic drug modulation.

This paper investigated the chemotactic capacity of blood eosinophils (EOS) in response to C5a and formyl-leucyl-phenylalanine (FMLP) in 15 Parietaria-pollen-allergic patients with mild asthma during the Parietaria pollen season. Data showed that EOS chemotaxis toward C5a was significantly reduced during the peak pollen count, compared with the values obtained in normal subjects. On the other hand, FMLP could induce EOS chemotactic activity only in Parietaria-allergic patients, the highest value being registered during the height of the Parietaria season. In vitro cimetidine modulation of chemotactic function in comparison with C5a led to a recovery of the impaired results obtained in the presence of high histamine levels. Moreover, diphenhydramine preincubation of EOS induced a reduction of the enhanced chemotactic activity obtained with low concentrations. The data suggest that different serum histamine levels give rise to an impaired immune-phlogistic response in allergic patients and that histamine-receptor antagonists may modulate this effect.