ADOPTIVE TRANSFER OF LYMPHOCYTES SENSITIZED TO THE MAJOR SURFACE GLYCOPROTEIN OF PNEUMOCYSTIS-CARINII CONFERS PROTECTION IN THE RAT

Pneumocystis carinii is a major opportunistic pathogen and a leading c ause of morbidity in patients with AIDS, CD4(+) cells have been shown to be important in host defenses against P. carinii, but the antigen(s ) involved with this response have not been identified, We undertook t he present study to determine whether the major surface glycoprotein ( MSG) of P. carinii contains epitopes that can elicit a protective cell ular immune response, Spleen cells and purified CD4(+) cells isolated from Lewis rats, pulsed 1-4 d with MSG, and injected into corticostero id-treated Lewis rats with pneumocystosis resulted in significant redu ction in the P. carinii burden, as judged by organism quantitation and lung histology, The protective response demonstrated by the donor cel ls was dependent on previous exposure to P. carinii, cell concentratio n, and time of incubation with MSG, In addition, reconstitution with M SG-specific CD4(+) cells resulted in an early hyperinflammatory respon se within the lungs of these animals with a high percentage of mortali ty, Thus, in this model, MSG can elicit an immune response mediated by CD4(+) cells, which has a harmful as well as helpful effect on the ho st, and these responses occur despite the presence of corticosteroids.