Utility of historical vehicle‐control data in the interpretation of the local lymph node assay

Abstract

The accepted approach to the interpretation of local lymph node assay (LLNA) data requires comparison of responses in the test groups with background activity found in concurrent vehicle-treated controls. However, of established value in the interpretation of toxicity test data is the use of historical control values that provide one criterion against which to judge the integrity of individual experiments. Specifically, the availability of robust and relevant historical control data permits examination of whether, in any individual experiment, control values fall within the expected range. With the most commonly used vehicle employed in the LLNA, acetone/olive oil (4 : 1) (v/v), the mean values, standard deviations and normal ranges are increasingly well established for a given laboratory, although there is some variation between laboratories, particularly with regard to expected ranges. Against this background, it is possible to identify (and, if appropriate, eliminate) a concurrent vehicle-control value that falls well outside the expected range. To explore critically the potential merits of this approach, one specific example is examined in detail.

Proliferative responses in the local lymph node assay associated with concomitant exposure to 1,4‐phenylenediamine and methyldibromo glutaronitrile: evidence for synergy?

“…Tables 1 and 2 show the data obtained in each of two independent experiments. The values obtained in each experiment for AOO [374 and 345 disintegrations per minute per lymph node (d.p.m./node)] compare well with historical values for this vehicle (9). Both PPD and MDBGN stimulated a dose‐dependent increase in lymph node cell proliferation.…”

The use of ethanol:diethylphthalate as a vehicle for the local lymph node assay

“…Third, there may be some variation within background levels of activity in the LLNA, even in the same laboratory, but in this particular case such changes appear not to affect the performance of the assay and the vigour of responses elicited by contact allergens. It should be noted that there are circumstances in which unusual control values (abnormally high or abnormally low values) may affect interpretation of LLNA data (21). It is therefore prudent for each laboratory that conducts the assay to monitor changes in levels of thymidine incorporation in vehicle‐treated control animals, and to consider on an individual assay basis whether control values fall outside the normal range for that laboratory and that are therefore potentially suspect.…”

Potency and risk assessment of a skin‐sensitizing disperse dye using the local lymph node assay

“…Exposure of control mice to the vehicle DMSO provoked somewhat higher levels of thymidine incorporation than those induced by application of DMF vehicle (values of 816 dpm, 885 dpm and 924 dpm per node recorded in the 3 experiments with DMSO compared with 582 dpm per node observed for control lymph nodes for DMF formulations) (Table 1). These background levels of thymidine incorporation are also higher than those generally observed for another common vehicle utilized in the LLNA, acetone : olive oil (AOO; 4 : 1), where a range of values of 97–662 dpm per node (mean dpm per node 321) were recorded for 1 laboratory over 44 experiments (19). Higher levels of background proliferation have been observed previously for DMSO vehicle, with values of 587–1173 dpm per node recorded (20, 21).…”