Antigen-induced non-specific suppressor factor in sheep efferent lymph is prostaglandin E2

Efferent lymph from the popliteal node of sheep challenged with antigen was found to suppress the in vitro transformation of sheep peripheral blood lymphocytes to a variety of antigens. The suppressor factor appeared 6-20 hr after challenged of the node and was shown to be prostaglandin E2, probably complexed to albumin.