Abstract
Summary Cells taken from draining lymph nodes one day after application of oxazolone and picryl chloride induced contact sensitivity in syngeneic but not in allogeneic recipients. In contrast, the immunizing activity of cells taken four days after sensitization was not genetically restricted. The findings that ‘1-day’ cells incubated with anti-hapten antibodies break down the genetic restriction, and that ‘4-day’ cells lose their ability to induce contact sensitivity after complement treatment, suggest that two different mechanisms are involved in the induction of contact sensitivity.