Long-term IgG4 determinations in hymenoptera-sensitive treated patients.

Honey bee and vespid venom immunotherapy have been practiced for the past 10 years. Several studies have evaluated the short-term effects of this therapy. The current study evaluated the long-term effects using venom-specific IgG4 determinations. Forty-six patients ranging in age from 3 to 67 years were followed for periods up to 6 1/2 years. All patients included in the study demonstrated Hymenoptera sensitivity on intradermal testing using 0.2 mL of venom extract at concentrations of 0.01 microgram/mL, 0.1 microgram/mL, or 1 microgram/mL. IgE-specific venom antibody levels were tested and found to be elevated. During the first year following institution of venom immunotherapy, 46/46 patients demonstrated an increase in venom-specific IgG4. After the first year of treatment, values reached a plateau. The IgG4 venom-specific antibodies remained relatively constant over the second and third years of the study. Thirty of the 46 patients were followed for more than 3 years. All of the 30, treated greater than 3 years with continuous immunotherapy, demonstrated a gradual decline in IgG4 levels. Despite very low or negligible levels of venom-specific IgG4 antibodies, six patients accidentally stung were still clinically protected. This study suggests that long-term immunity is not mediated in the same manner as that of short-term protection.