Evaluation of contact sensitivity of rubber chemicals using the murine local lymph node assay

The sensitizing abilities of 4 rubber additives, tetramethylthiuram disulfide (TMTD). 2-mercaptobenzothiazole (MBT), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD) and zinc diethyldithiocarbamate (ZDEC), were evaluated using the murine local lymph node assay. Exposure to IPPD induced a significant increase of lymph node cell proliferation in the draining lymph nodes even at a low concentration. Exposure to TMTD and MBT induced moderate proliferative responses, while ZDEC induced a weak proliferation even at the higher concentrations. The sensitizing potency of each chemical was described in terms of the concentration that increased lymph node cell proliferation by a factor of 2 over that in the vehicle-treated control group. The concentrations of IPPD, TMTD, MBT and ZDEC were 0.14%, 0.35%, 4.2% and > 10%, respectively.