Local lymph node assay (LLNA)
The Local Lymph Node Assay (LLNA) is the gold standard nonclinical toxicology test for skin sensitization, namely to identify the immunogenic and allergenic properties of the active pharmaceutical ingredient (API).
In the test, rodent species are exposed to the API and examined after several days for T cell proliferation. LLNA measures the response of the lymph nodes to the API.
Sensitization is mediated by lymphocytes that recognize the API as a foreign substance and start to divide and increase in number. The LLNA provides a quantitative measurement.