TABLE 1.

Virus-positive macrophages in primary cultures^a

Virus strain	% Virus-positive macrophages
	10 h p.i.	24 h p.i.
DAb	6.22 ± 0.57	10.89 ± 1.18
GD VIIc	3.28 ± 0.65	1.17 ± 0.18
R2c	2.17 ± 0.28	1.14 ± 0.25
R3b	3.72 ± 0.45	5.17 ± 1.05

^aViral antigens were detected by immunofluorescence (see Fig. 2). Nuclei were stained with ethidium homodimer 1. The percentage of virus positive-cells was measured 10 and 24 h p.i. All cells containing green fluorescent dots were counted as virus positive. The table shows the results of four independent experiments. Values are means ± standard errors of the means.

^bAt 10 h p.i., positive cells had intense, uniform cytoplasmic labeling (TMEV^hi).

^cThe fluorescent signal at 10 h p.i. was mainly in a weak, punctate pattern (TMEV^lo).