THE MOUSE IgE TEST: INTERLABORATORY EVALUATION AND COMPARISON OF BALB/c AND C57BL/6 STRAIN MICE

The mouse IgE test is a novel method for the prospective identification of chemicals that have the potential to cause allergic sensitization of the respiratory tract. Activity is measured as a function of increases in the concentration of total serum IgE induced by topical exposure of mice to chemicals; those chemicals that elicit a substantial elevation in IgE are classified as respiratory allergens. The present investigations were designed to evaluate further the utility of the mouse IgE test. For this purpose theassay was conducted in each of fiveindependent laboratories using trimellitic anhydride (TMA), a known cause of respiratory sensitization and occupational asthma, and 2,4-dinitrochlorobenzene (DNCB), a potent contact allergen that is considered not to cause sensitization of the respiratory tract. For these investigations BALB/c mice were used, which are currently the strain of choice for the mouse IgE test. In four of five laboratories, exposure of mice to TMA caused a statistically significant increase in the serum concentration of IgE. Under the same conditions of exposure, DNCB failed in all laboratories to induce a significant change in IgE levels compared with vehicle-treated controls. In three of five laboratories, the concentration of total serum IgE was greater in TMA- than in DNCB-treated mice. The concentration of IgE in the sera of mice exposed to vehicle alone was not significantly different from that found in untreated (naive)animals. Although thedifferential ability, in some instances, of TMA and DNCB to provoke increases in serum IgE is consistent with the results of previous investigations, it was found in all five laboratories that there existed considerable variation among individual mice within experimental groups with respect to IgE levels. These data mirrored an increasing variability in serum IgE concentrations among BALB/c strain mice found in one of the participating laboratories. For this reason mice of another strain (C57BL/6) were evaluated in the mouse IgE test by the same laboratory. The data presented here reveal that C57BL/6 mice display more stable serum IgE levels and a lower constitutive level of serum IgE but nevertheless exhibit differential responses to TMA and DNCB, with only the former causing a substantial increase in IgE concentrations. Collectively these results suggest that although the mouse IgE test continues to show some promise as an approach to the identification of chemical respiratory allergens,