Table 1.

Histopathologic lesion and cyst scores and Western immunoblot and PCR results in rats during methylprednisolone inductiona

Animal no.Weeks of inductionPulmonary histopathologyWestern immunoblotting (no. positive/no. tested)PCR (no. positive/no. tested)
Overall inflammationPneumocystosis lesionsbGMS cyst scoreb (no. positive/no. tested)PreinductionTerminal
40–4210.660.330.00 (0/3)3/33/32/3
43–4521.001.001.33 (3/3)3/33/33/3
46–4831.000.331.33 (3/3)1/32/33/3
49–5141.000.662.00 (3/3)0/32/32/3
13–1541.001.001.33 (3/3)2/32/32/3
16–1851.331.662.00 (3/3)3/32/32/3
19–2160.661.001.33 (3/3)3/33/31/3
22Died NDc NDNDNDNDND
23–2481.501.503.00 (2/2)1/22/22/2
  Total or avg1.020.941.54 (20/23)16/2319/2318/23
  • a Histopathologic grading scales are as follows. Overall pulmonary inflammations (hematoxylin and eosin sections): 0, no discernible inflammation; 1, inflammation affecting less than 25% of examined tissue; 2, inflammation affecting 25 to 50% of examined tissue; 3, inflammation affecting 50 to 75% of examined tissue; 4, inflammation affecting over 75% of examined tissue.Pneumocystis lesions (hematoxylin and eosin sections): 0, no microscopic evidence of Pneumocystis infection; 1, multifocal poorly defined areas of inflammation consistent withPneumocystis infection; 2, one or two well-defined areas of alveolar filling highly suggestive of Pneumocystisinfection; 3, more than two well-defined areas of alveolar filling highly suggestive of Pneumocystis infection.Pneumocystis forms (Gomorri’s methenamine silver sections): 0, no cysts seen; 1, rare single cysts seen at a rate of less than 1 per 10 40× fields; 2, 1 to 10 cysts per 10 40× fields; 3, 10 to 100 cysts per 10 40× fields; 4, >100 cysts per 10 40× fields.

  • b Means of groups of three rats.

  • c ND, not done.