The local lymph node assay in practice: a current regulatory perspective

Abstract

<jats:p> Following the formal acceptance of the local lymph node assay (LLNA) as an Organization for Economic Cooperation and Development (OECD) guideline in April 2002, the UK Health and Safety Executive (HSE) informed notifiers that this was now the method of choice for the assessment of skin sensitization potential under the EU notification scheme for new industrial chemicals (NONS). This paper summarizes the experience of the HSE for the 2-year period immediately following the issuing of this statement, during which 48 LLNA study reports were assessed for notification purposes. The issues discussed here include adherence to the OECD guideline, interpretation of results, and classification outcomes. Generally, notifying laboratories followed the OECD guideline successfully, with regard to the sex/ strain/numbers of mice used, the precise process used for measurement of cell proliferation, and the use of recommended vehicles and positive controls. Initially, use of the individual animal approach (measuring the cell proliferation in each animal rather than for a pooled dose group) highlighted problems caused by technical inexperience, but these were overcome by practice. Toxicity or irritation were found to be minor factors in dose selection; more important was the choice of vehicle to correctly maximize the test substance concentration, while maintaining appropriate application properties. Contrary to concerns that the LLNA would prove to be less sensitive or more sensitive than the traditionally used Guinea Pig Maximization Test (GPMT), the proportion of new substances classified as skin sensitizers was within the range observed in previous years. Although the sample size is relatively small, the experience of the HSE indicates that the LLNA is satisfactory for routine regulatory use. </jats:p>

Comparative Studies of Lymph Node Cell Subpopulations and Cytokine Expression in Murine Model for Testing the Potentials of Chemicals to Induce Respiratory Sensitization

“…The development of models for assessment of the potentials of LMW chemicals to induce allergic reactions is an important task for occupational health care professionals and the decisions they undertake establishing safe exposure limits. The local lymph node assay (LLNA) is now a validated method for assessing the potentials of chemicals to induce skin contact allergy [3][4][5][6]. However, until now, there is no validated method to assess the potentials of chemicals to induce respiratory sensitization.…”

An improvement of LLNA:DA to assess the skin sensitization potential of chemicals

“…Woolhiser MR assessed the response of chemical sensitizers in the LLNA across 6 strains of female mice, and concluded that "DBA/2, B6C3F1 and BALB/c mice are good choices for continued evaluation as additional mouse strains for use in the LLNA" (Woolhiser et al, 2000). Other studies also showed that BALB/c mice may have small differences compared with CBA mice (Cockshott et al, 2006;Guo et al, 2013). Since the OECD guidelines state that "other strains and males may 2.74 a Values are expressed as the mean ± S.D.…”

Skin Irritation and Sensitization: Mechanisms and New Approaches for Risk Assessment

“…After the formal validation of the assay, some groups thought that it may be too sensitive and/or prone to false positives [53,54] . This topic has been extensively discussed in the literature [41,[54][55][56][57] . It is a fact that any toxicology assay has both false positives and false negatives, and the LLNA is no exception.…”