EXPERIMENTAL HYPERSENSITIVITY PNEUMONITIS - EFFECT OF CD4 CELL DEPLETION

We previously demonstrated that Thy1.2(+), CD4(+), Ia(-) T cells are r esponsible for transfer of adoptive murine experimental hypersensitivi ty pneumonitis (adoptive EHP). To characterize the cells responsible f or development of pulmonary inflammation in the recipient animals, we depleted recipients of CD4(+) cells using monoclonal antibody GK1.5 be fore administration of Micropolyspora faeni-sensitized cultured C3H/He J spleen cells (SC) and intratracheal (i.t.) challenge with M. faeni. We also used the same depletion technique to determine the contributio n of these cells to the pulmonary response to i.t. M. faeni in animals that did not receive cultured cells (direct EHP). The nature and exte nt of pulmonary inflammatory changes in these animals were assayed eit her 4 days after i.t. challenge with M. faeni in adoptive EHP or 2 day s after i.t. challenge with M. faeni in direct EHP. Cultured M. faeni- sensitized SC could transfer EHP to naive animals or those treated wit h an irrelevant antibody. Depletion of CD4(+) cells ablated the abilit y of recipient animals to express adoptive EHP. Two days after i.t. M. faeni (direct EHP), there was extensive neutrophilic infiltration of the lung that was not affected by depletion of CD4(+) cells. We conclu de that the ability to express adoptive EHP is dependent on the presen ce of CD4(+) cells. In contrast, the acute inflammatory response to M. faeni is not CD4(+) cell dependent.