(184) Feasibility and Immunological Impact of Reusing Wild-Type C57BL/6 Mice in Systemic and Cutaneous Anaphylaxis Models

Introduction/Rationale: The reuse of laboratory animals across compatible immunological procedures offers a strategy to reduce animal numbers in line with the 3Rs principles. However, data on the physiological and immune effects of consecutive allergic or anaphylactic challenges remain limited. This study evaluated the feasibility and immunological impact of reusing C57BL/6 mice previously exposed to systemic anaphylaxis for a second moderate-severity challenge, either systemic or cutaneous.

Methods: Twenty-four 7-week-old male mice received an intravenous injection of compound 48/80 to induce systemic anaphylaxis (Run 1). Body temperature, hematological and cytokines were monitored at baseline, after Run 1, and on Day 5 before reuse. Seven days later (Run 2) mice underwent either a second systemic challenge or a cutaneous anaphylaxis via intradermal ear injection with mast cells agonists, combined with Evans Blue to monitor vascular permeability.

Results: During Run 1, transient hypothermia peaked 20–30 min post-induction, with full recovery within 80 min. In Run 2, the temperature drop was milder, and no mouse fell below 34 °C. Neutrophils transiently increased after Run 1 and returned to baseline, while lymphocytes showed the opposite trend. Cytokine concentrations increased after the first systemic challenge, returned to baseline and remained stable after the second exposure.
Cutaneous responses and Evans Blue extravasation were comparable to single-use animals, confirming preserved immune and vascular responsiveness. No major modulation of other hematological parameters , and no behavioral distress were observed.

Conclusion: These findings demonstrate that mice can be safely reused for a second systemic or cutaneous anaphylaxis procedure after 5–7-days,with no exacerbation of immune or physiological responses, supporting ethical and scientific validity of controlled animal reuse in preclinical allergy research.