National Toxicology Program

Overview

The murine local lymph node assay (LLNA) is a stand-alone test method for assessing the potential of a test substance to induce allergic contact dermatitis. In January 2007, the U.S. Consumer Product Safety Commission (CSPC) requested that NICEATM and ICCVAM assess the validation status of new versions and applications of the LLNA.

The ICCVAM Immunotoxicity Working Group (IWG), working with NICEATM, prepared draft background review documents (BRDs) and draft recommendations for application of the LLNA for evaluating pesticide formulations and other products, and for three modified versions of the LLNA not requiring the use of radioactive markers. The draft BRDs and draft ICCVAM recommendations were reviewed in a public meeting of an international independent scientific peer review panel (“Panel”) in March 2008. The Panel agreed with the ICCVAM assessment that more data were needed to evaluate these new versions and applications of the LLNA. Additional data were submitted to NICEATM; NICEATM and the IWG revised the BRDs, and updated test method recommendations were developed by ICCVAM. A second Panel meeting to consider the revised documents was held on April 28-29, 2009; the Panel's report will be available in June.

View a summary of the April 2009 Panel meeting [PDF]

The Panel concluded that the available data and test method performance support the use of two of the non-radioactive modified versions of the LLNA, the LLNA: DA and the LLNA: BrdU-ELISA, to identify substances as potential skin sensitizers and nonsensitizers, with certain limitations. They agreed with ICCVAM’s proposal that, based on the current validation database, multiple stimulation index (SI) decision criteria should be used to identify sensitizers and nonsensitizers for each of the two methods. The Panel also noted that the limitation of these test methods when using the proposed multiple decision criteria is the indeterminate classification of substances that fall in the range of SI values for which a classification is uncertain. The Panel recommended that when such results are obtained, users should carefully interpret the results in an integrated decision strategy in conjunction with all other available information (e.g., dose response and QSAR information, statistical analyses, peptide-binding activity, molecular weight, results from related chemicals, other testing data) to determine if there is adequate information for an accurate sensitization hazard classification or if additional testing is necessary. The Panel agreed with the ICCVAM proposal to defer a formal recommendation on the validity of the LLNA: BrdU-FC until an independent audit of all data supporting the analysis has been conducted and until transferability has been demonstrated in an interlaboratory validation study.

With regard to the applicability of the LLNA for testing pesticide formulations and other products (e.g., natural complex substances, dyes, aqueous solutions), the Panel concluded that any material should be suitable for testing in the LLNA unless there is a biologically-based rationale for exclusion, such as unique physicochemical properties that might affect the ability of the material to interact with immune processes. The Panel therefore concluded that the LLNA should be considered appropriate for testing pesticide formulations and other products, unless there is a biologically-based rationale for exclusion.

ICCVAM will consider the Panel’s report along with all public and SACATM comments received, and prepare final test method recommendations that will be forwarded to Federal agencies for their consideration later in 2009.

Announcement of a Second Meeting of the Independent Scientific Peer Review Panel on the Murine Local Lymph Node Assay; Availability of Draft Background Review Documents (BRD); Request for Comments

Peer Review Panel Report on the Validation Status of New Versions and Applications of the Murine Local Lymph Node Assay (LLNA): A Test Method for Assessing the Allergic Contact Dermatitis Potential of Chemicals and Products: Notice of Availability and Request for Public Comments

Announcement of an Independent Scientific Peer Review Panel Meeting on the Murine Local Lymph Node Assay; Availability of Draft Background Review Documents; Request for Comments

Murine Local Lymph Node Assay: Request for Comments, Nominations of Scientific Experts, and Submission of Data

Information about the 1998 LLNA Peer Panel meeting