FIG. 3.
Effects of heat treatment, MDC, and oxytetracycline on TfR mRNA expression. (a) THP-1 cells (5 × 106) were treated with MDC (250 μM, 3 h preinfection; bottom row) or oxytetracycline (10 μg/ml, 6 h postinfection; middle row) and incubated with live host-cell free E. chaffeensis (derived from 107 infected cells) or were incubated with heat-killed E. chaffeensis (top row). After incubation, total RNA was extracted and cDNA was synthesized as described in Materials and Methods. An aliquot of the PCR product (9 μl) was visualized on a 1.5% ethidium bromide-agarose gel. Lanes are as in Fig. 2a. (b) Approximate TfR mRNA concentrations at 0, 3, 6, 12, 18, 24, 48, and 72 h based on a standard curve. Values are the means and standard deviations of three independent experiments for each Ehrlichia species.