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 identificatio n, of chemicals that have the potential to cause allergic sensitizatio n of the respiratory tract. Activity is measured as a function of incr eases in, the concentration, of total serum IgE induced by topical exp osure 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 mo use IgE test. For this purpose the assay was conducted in each of five independent laboratories using trimellitic anhydride (TMA) a known ca use of respiratory sensitization and occupational asthma, and 2,4-dini trochlorobenzene (DNCB), a potent contact allergen that is considered not to cause sensitization of the respiratory tract. For these investi gations BALB/c mice were used, which are currently the strain of choic e for the mouse IgE test. In four of five laboratories, exposure of mi ce to TMA caused a statistically significant increase in the serum con centration of IgE. Under the same conditions of exposure, DNCB failed in all laboratories to induce a significant change in IgE levels compa red with vehicle-treated controls, in three of five laboratories, the concentration of total serum IgE was greater in. TMA- than. in DNCB-tr eated mice. The concentration of IgE in the sera of mice exposed to ve hicle alone was not significantly different from that found in untreat ed (naive) animals. Although the differential ability, in some instanc es, of TMA and DNCB to provoke increases in serum IgE is consistent wi th the results of previous investigations, it was found in all five la boratories 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. Fo r this reason mice of another strain (C57BL/6) were evaluated in the m ouse IgE test by the same laboratory. The data presented here reveal t hat C57BL/6 mice display more stable serum IgE levels and a lower cons titutive level of serum IgE but nevertheless exhibit differential resp onses to TMA and DNCB, with only the former causing a substantial incr ease in IgE concentrations. Collectively these results suggest that al though the mouse IgE test continues to show some promise as an approac h to the identification of chemical respiratory allergens there is a n eed for careful consideration of the strain, of mouse used before the assay can be considered fully optimized.