IL-2-like activity in lymph fluid following in vivo antigen challenge

The majority of studies that characterize lymphokines utilize in vitro activation of lymphocytes. In an attempt to identify and characterize lymphokines released from tissue sites, we have cannulated sheep lymphatic vessels and collected lymph that drains a site of in vivo antigen challenge. Lymph draining directly from a site of intradermal antigen challenge (afferent lymph) and lymph draining an antigen-stimulated lymph node (efferent lymph) were assayed for lymphokine activity by the ability of cell-free lymph fluid to stimulate the proliferation of sheep Con A-blasts. Afferent and efferent lymph, both collected at 24 and 48 hr following in vivo antigen challenge, with either ovalbumin or PPD in primed animals, stimulates the proliferation of sheep Con A-blast cells. This in vivo-derived lymphokine activity and in vitro-generated sheep Con A supernatant has an active component with properties similar to interleukin-2 (IL-2) that has been described in several other species. The IL-2-like material is precipitated by 40-80% ammonium sulphate saturation, has a molecular weight (MW) of 20,000 MW as judged by gel filtration chromatography, and is eluted from an anion-exchange HPLC column with 125 mM NaCl. HPLC ion-exchange fractionation of the 20,000 MW material from lymph fluid shows differences between afferent and efferent lymph material. The fractionation of afferent material is similar to that of in vitro generated Con A supernatant material with a single peak of activity eluted by 125 mM NaCl. In contrast, the 20,000 MW material from efferent lymph elutes with peaks of activity at 125 and 300 mM NaCl.