FIG. 2.

(A) The time course of TfR upregulation by C. burnetii infection was determined by immunoblotting. J774A.1 cells were inoculated with viable or inactivated C. burnetii. At designated time points, TfR expression was examined by immunoblot analysis. The optical density of bands was determined by scanning densitometry. TfR expression in cultures inoculated with inactivated C. burnetii show no increase in density, while infection with viable C. burnetii causes densities to increase by 24 h to 4.5 times that seen in uninoculated cells. Results shown are the mean of four experiments, with error bars indicating standard errors. Student t tests indicate that there is a significant difference in the optical density of TfR bands from infected samples taken at 9, 12, and 24 h and that for P < 0.1 (a) for P < 0.05 (b) and for P < 0.001 (c). (B) Representative immunoblots used to generate the data shown in panel A. Lane 12d shows TfR expression at 12 h by uninoculated J774A.1 cells.