Alteration of surfactant proteins A and D in bronchoalveolar lavage fluid of pneumocystis carinii pneumonia

Objective To understand the interaction between surfactant proteins and pne umocystis carinii pneumonia (PCP), and the impact of corticosteriods on sur factant proteins. Methods We established rat models of PCP and bacterial pneumonia induced by subcutaneous injection of 25mg cortisone acetate. At 8 - 12 wk, the bronch oalveolar lavage fluid (BALF) of rats was collected. Total nucleated cells of BALF were counted and differentiated, and the concentrations of surfacta nt protein A (SP-A) and surfactant protein D (SP-D) were measured by immuno blotting assay. The rats were divided into three immunosuppressive groups a nd a normal control group. Group I, normal control (n = 6), consisted of he althy SD rats; group U, negative control (n = 6), consisted of rats with co rtisone acetate injection for over 8 wk without lung infection; group III, bacterial pneumonia (n = 11), rats were injected with cortisone acetate ove r 8 wk that resulted in bacterial pneumonia without other pathogens isolate d; and group IV, PCP (n = 14), rats with injected cortisone acetate for 8 - 12 wk and developed PCP without other pathogens isolated. Results Our results indicated that the total cell count in BALF in the nega tive control group was lower than that in the normal control group ( P < 0. 001). During PCP infection, the total cell count and the percentage of poly morphonuclearcytes (PMNs) in BALF were significantly increased ( P < 0.01), but were lower than those in the bacterial pneumonia group. The concentrat ion of SP-A of BALF in PCP (45.1 +/- 22.1 mug/ml) was significantly increas ed in comparison with that in the negative control (16.2 +/- 9.9 mug/ml, P < 0.05) and bacterial pneumonia groups (6.2 +/- 5.6 mug/ml, P < 0.001). We also found that the relative content of SP - D was significantly higher in PCP (24 249 +/- 4780 grey values) than that in the negative control (13 384 +/- 2887 grey values, P < 0. 001) and that in bacterial pneumonia (111989 +/- 2750 grey values, P < 0.001). SP-A and SP-D were also higher in the mod erate to heavy group of PCP than those seen in the mild group ( P < 0.01, P < 0.001). SP-A and SP-D were higher in the negative control group than tho se in the normal control group, but there was no significant difference bet ween the 2 groups. Conclusion These results suggest that the concentrations of SP-A and SP-D i n BALF are increased by pneumocystis carinii specific stimulation, but the alteration is not related to the corticosteriod usage.