The local lymph node assay: past, present and future

Abstract

The local lymph node assay (LLNA) was developed originally as a method for the identification of chemicals that have the potential to cause skin sensitization and allergic contact dermatitis. The assay is based on an understanding that the acquisition of contact sensitization is associated with, and dependent upon, the stimulation by chemical allergens of lymphocyte proliferative responses in skin-draining lymph nodes. Those chemicals that provoke a defined level of lymph node cell (LNC) proliferation (a 3-fold or greater increase compared with concurrent vehicle controls) are classified as skin sensitizers. Following its original inception and development, the LLNA was the subject of both national and international interlaboratory collaborative trials, and of very detailed comparisons with other test methods and with human skin sensitization data. The assay has now been validated fully as a stand-alone test for the purposes of hazard identification. In recent years, there has been a growing interest also in the use of the LLNA to assess the potency of contact allergens and in risk assessment. There is reason to believe that the extent of skin sensitization achieved is associated with the vigour of LNC proliferation induced in draining nodes. Given this relationship, the relative potency of skin sensitizing chemicals is measured in the LLNA by derivation of an EC3 value, this being the concentration of chemical required to provoke a 3-fold increase in the proliferation of LNC compared with controls. Experience to date indicates that relative potency as determined using this approach correlates closely with what is known of the activity of skin sensitizing chemicals in humans. In this article, we review the development, evaluation and validation of the LLNA for the purposes of hazard identification, and the more recent application of the method for evaluation of potency in the context of risk assessment. In addition, we consider what new applications and modifications are currently being investigated.Key words: allergic contact dermatitis; hazard identification; local lymph node assay; lymphocyte proliferation, potency assessment; risk assessment; skin sensitization. C Blackwell Munksgaard, 2002. C Blackwell Munksgaard, 2002. Accepted for publication 28 October 2002Skin sensitization resulting in allergic contact dermatitis is an important occupational disease, and certainly the most common manifestation of chemical allergy in humans. There is a need therefore to identify the hazards and risks of allergic contact dermatitis that may be associated with exposure to chemicals at work, at home and in the environment. Conventionally, toxicological assessments of this kind are conducted (conceptually at least) in 2 phases, wherein potential hazards are first identified and then the likelihood of those hazards translating into human health risks is assessed. The latter risk assessments are predicated upon consideration of the nature of the hazard (of particular importance being an appreciation of potency) and the likel...

A roadmap for the development of alternative (non-animal) methods for systemic toxicity testing

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Evaluation of auricular lymph node cell lymphocyte proliferation and cytokine production as non-radioactive endpoints during murine contact allergy

“…The EC 3 value is the measurement of the relative skin sensitizing potency of a substance, usually expressed as the estimated concentration of chemical necessary to produce a 3-fold increase in proliferation in draining lymph nodes compared with concurrent vehicle-treated controls (Kimber et al, 2002). The method represents a simple linear interpolation of the points in the dose-response curve, which lie immediately above and below the classification threshold, i.e.…”

Evaluation of Allergenicity of Constituents of Myoga Using the Murine Local Lymph Node Assay

“…The effective concentration of a stimulation index of 3 (EC3) for each experimental group was calculated by linear interpolation (IS, [20][21][22][23][24]. In each case, a stimulation index (SI) relative to the concurrent vehicletreated control was derived.…”