Serum IgG antibody response to Pneumocystis carinii among immunosuppressed, malnourished and healthy rats.

Pneumocystis carinii is an important opportunistic pulmonary pathogen that causing pneumonia in premature infants, children with immunodeficiency diseases and patients of all ages receiving immunosuppressive agents. In this work, humoral immune responses to this organism were studied, using IFAT during the period of infection and recovery of immunosuppressed and malnourished rats compared to healthy group. Where sever pneumonitis similar to that seen in humans can be induced in this experimental model. Serum IgG antibody titers to the organism were absent in rats administered corticosteroids but rose after steroid tapering with disappearance of the organism from their lungs due to reactivation of the immune system. While in malnourished infected rats, clearance of the organism had occurred after regaining the protein diet with progressive increase in IgG level denoting their immunocompetent state. IgG antibody appeared in the serum of control healthy rats with the progress of age at low non diagnostic level indicating the presence of dormant parasites in their lungs.