PRURITOGENIC EFFECTS OF MITOGEN-STIMULATED PERIPHERAL-BLOOD MONONUCLEAR-CELLS IN ATOPIC ECZEMA

The etiology of atopic pruritus is unclear and seems mostly histamine- independent. In order to investigate non-mast cells as possible source s of pruritogenic agents, peripheral blood mononuclear cells from 12 a topic eczema patients and 12 controls were incubated in vitro for 24 h with phytohemagglutinin or concanavalin A (both at 10 mu g/ml) or wit h medium alone, and each subject was tested with his own cell supernat ants and lysates by prick testing and by application on tape-stripped skin, Histamine (0.1%) and substance P (500 mu M) were tested in compa rison, and reactions were observed for up to 24 h, Cell supernatants w ere also analysed for their contents of several cytokines. Lymphocyte cell extracts or supernatants failed to cause symptoms in controls but induced whealing in 6 and itching in 3 patients on prick testing with in 5 min, lasting for 30 min in 2 patients and persisting for 6 h in 1 patient. Histamine caused itching in all controls and in 7 patients w ithin 5 min on prick testing, with decreasing reactivity at later time s. Substance P yielded results with lower values, With all three types of test reagents, fewer subjects reacted on tape stripped skin, High levels of interleukins 2 and 6, low levels of interferon and no detect able levels of interleukin 4 and tumour necrosis factor were measured in stimulated cell supernatants and extracts, with even lower levels i n subjects exhibiting skin reactivity, These findings thus provide evi dence that as yet unidentified mononuclear cell products may be involv ed in whealing and itching associated with atopic eczema.