Modulation of venom-induced leukocyte histamine release by mononuclear cells: effect of venom immunotherapy.

Leukocyte histamine release and blood mononuclear cell proliferative responses to venoms were evaluated in nine patients with sting anaphylaxis. The effect of venom-activated mononuclear cells on the autologous mononuclear cell proliferative response and venom-induced leukocyte histamine release was also studied before and on maintenance immunotherapy. The mononuclear cell proliferative response was low (specific incorporations less than 2.0) and antigen nonspecific both before and during maintenance immunotherapy. Venom-induced in vitro leukocyte histamine release did not change significantly with immunotherapy. However, when patients were on maintenance immunotherapy, venom-activated mononuclear cells cocultured with autologous leukocytes significantly (p less than 0.05) suppressed venom-induced histamine release. The suppressive effect of mononuclear cells was antigen specific and enhanced by in vitro mononuclear cell activation. Suppression of leukocyte histamine release by mononuclear cells extends the regulatory potential of these cells and may identify an additional mechanism by which immunotherapy protects Hymenoptera-sensitive individuals against systemic anaphylaxis.