A quantitative lymphocyte localization assay.

Multiple lesions (up to 100 sites) were induced in the skin of sheep using either allogeneic lymphocytes or, in BCG-sensitized animals, tuberculin. Cells recovered from an indwelling lymph catheter draining a prescapular lymph node were labeled with 111-indium, returned to venous blood, and allowed to circulate for 3 hours. Sheep were killed, and the skin lesions and lymph nodes were removed and counted in a gamma spectrometer. High levels of radioactivity (up to 38,000 cpm/lesion) were recovered from lesions, and only a few hundred cpm were recovered from comparable normal skin sites. Dose-response relationships and time kinetics were demonstrated for these lesions, and the radioactivity on blood and lymph cells was measured. The contribution of cell-free radioactivity was negligible. Using replicate injection sites, analytical, internally controlled studies can now be initiated to study the induction, promotion, and suppression of lymphocyte traffic.