Popliteal Lymph Node Assay
The popliteal lymph node assay (PLNA) is in use to test the immunostimulatory capacity of low molecular weight compounds, in particular pharmaceuticals. Briefly, compounds are injected subcutaneously into the hind footpad of either mice or rats, and 6–8 days later the draining popliteal lymph node (PLN) is excised and compared with popliteal lymph nodes from vehicle-treated animals. Comparison is basically made between the weight and the cellularity of the nodes; the ratio of these parameters from compound-treated over vehicle-treated PLNs (designated the PLN index) indicates whether or not the compound is immunostimulatory. Immunostimulation is regarded as one of the possible prerequisites for pharmaceuticals and other compounds to activate and sensitize T cells and to induce systemic allergy or autoimmune-like derangements.
In the late 1970s and early 1890s, Gleichmann and colleagues realized that graft-versus-host (GvH) reactions...