Evaluation of delayed type hypersensitivity to beta-lactam antibiotics in mice

This study was designed to determine whether delayed type hypersensitivity could be evoked by protein-unconjugated beta-lactam antibiotics emulsified with Freund's complete adjuvant (FCA) in mice. The method providing the strongest sensitization was assessed by measuring footpad swelling induced by several biweekly intervals of subcutaneous injections of 0.8 mg/mouse cephalothin with FCA, followed by intradermal challenge with 1.0 mg/site cephalothin into the footpad in four different strains of female mice. A total of three and four injections, once every two weeks, in BDF1 and DBA/2 mice, respectively, produced the greatest potential for swelling. This swelling could be reinduced by the local passive transfer of cephalothin-primed splenocytes into the footpad of naive recipient mice. Moreover, the reaction was diminished by the addition of anti-Thy-1.2 monoclonal antibody with low-toxicity rabbit complement to cephalothin-primed splenocytes. Swelling in the footpad was therefore induced via the delayed type hypersensitivity reaction, indicating T-lymphocyte dependence. When the potential for beta-lactam antibiotics to elicit delayed type hypersensitivity was investigated in BDF1 mice, eight of the nine agents employed showed a 10-90% positive incidence. This result had a significant correlation (r = 0.76) with the data for skin reaction in guinea pigs, the method generally used for estimating allergenicity. These results suggest that this procedure may be a useful tool for evaluating delayed type hypersensitivity induction during the early development of novel antibiotics, since not only can sensitization be induced with protein-unconjugated antibiotic, but also because assessment can be made using a small amount of sample.