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The
Mouse Local Lymph Node Assay is now accepted by the EPA, OECD,
and FDA as the preferred "stand-alone alternative" to the Guinea
Pig Sensitization Test. MB Research offers a "Standard LLNA" (OECD TG429 and EPA OPPTS 870.2600). In addition, for problem test substances and irritants, MB Research also offers an "Enhanced LLNA" using Flow Cytometry to allow
the evaluation of optional immunophenotypic markers which discriminate
"true sensitizers" from "false-positive irritants".
During the
"induction phase" of sensitization, following exposure to a
sensitizing test substance, lymphocyte proliferation occurs
in the local lymph node. The LLNA measures increased proliferation
of lymphocytes in the auricular lymph nodes (which drain the
site of exposure; ears). Proliferation is assessed by determining
the incorporation of the thymidine analog, bromodeoxyuridine
(BrdU), into the DNA of lymph node cells using flow cytometric
method. This "Enhanced LLNA" reduces background noise
and false positives, by quantitatively assessing irritation,
(via ear swelling) and by incorporating optional immunophenotype
analysis to resolve and discriminate false-positive irritants(%B220+,
CD3+, CD69+, I-Ak+ cells).
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