A METHOD FOR TRACKING THE MIGRATION OF BLOOD LYMPHOCYTES

A method has been devised for labeling whole blood with the fluorescent dye fluorescein isothiocyanate (FITC) so the migration of blood lymphocytes can be studied in the sheep. Although lymphocytes can be purified from blood using density gradient media or elutriation it is difficult to obtain a large number of cells, because many cells are usually lost during the purification steps. It is desirable to label at least 108–109 lymphocytes for lymphocyte tracking studies, because a smaller number is difficult to subsequently detect and quantitate in blood and lymph even using flow cytometry. Also, it is desirable to minimize the in vitro manipulation of lymphocytes, because dead or damaged lymphocytes will not recirculate. By labeling all the cellular components of a sample of whole blood rather than first purifying the lymphocytes we have been able to satisfy both of these criteria. Although labeled blood cells of all types are reinjected into the animal, the lymphocytes are easily distinguishable from othe...