“…This is in contrast to our knowledge about the properties of cytotoxic T lymphocytes (Tc) generated dtiring viral infection in man [4,26] and the mouse [9,II,12,39]. Furthermore, adoptive transfer experiments suggest that cell preparations enriched for Tc activity redtice lung virus titres in mice given a lethal dose of virus and prevent the mice from dying [41,42], It has been suggested that DTH reactions, on Ihe other hand, contribute to the pathology of the infectious process. Definitive experitnents to establish this have yet to be carried out, however, and this cannot be done until more is known about the effector cells that take part in DTH reactions (Td) and the conditions for their generation.…”