Oral Tolerance in Active Fatal Anaphylaxis

Lee, Hern Ku

Abstract

We have investigated whether oral administration of ovalbumin (OVA) could prevent active systemic anaphylaxis to the antigen. Oral tolerance was induced by a single feecfing with 40 mg OVA before, but not after, sensitization characterized by diminished OVA-specific IgE and IgG responses. Feeding 15 mg OVA suppressed anaphylaxis and antibody responses to a lesser extent. Spleen cells from tolerant donors were incapable of transferring the tolerance to naive recipients. Pretreatment of cyclophosphamide (100 mg/kg) 2 days before OVA feeding did not restore the tolerance. Furthermore, in vitro cell mixing studies showed that the proliferation of spleen cells from OVA- sensitized donors was not inhibited by the addition of spleen cells from tolerant donors, arguing against the role of suppressor cells. Anergy was demonstrated by the ability to reverse the tolerant state after culturing tolerant cells in the presence of IL-2. These findings indicate that only a high-dose (40 mg) feeding OVA was found to be effective in inducing tolerance in this experimental system, and demonstrate anergy as the mechanism underlying oral tolerance to systemic anaphylaxis.