TABLE 1.

Virus persistence in the lymphoid tissue of Ig^+/+ and Ig^−/− mice^a

Organ	Mouse strain	Mean no. of infectious centers/107 lymphocytesb		Log10 PFU of virus/ml of culture supernatantc
		Day 15	Day 40	Day 15	Day 40
MLN	B6	150	5	4.0 × 102	2.3 × 106
	μMT	0	0	1.7 × 104	1.9 × 106
CLN	B6	200	4	3.0 × 104	1.3 × 104
	μMT	0	0	1.4 × 101	1.5 × 103
Spleen	B6	400	10	4.0 × 102	0
	μMT	0	0	2.1 × 104	4.0 × 102

^aThe Ig^+/+ (B6) and Ig^−/− (μMT) mice were infected i.n. with 600 PFU of γHV-68, and samples of the mediastinal lymph nodes (MLN), cervical lymph nodes (CLN), and spleen were taken 15 and 40 days later for assay (7). In both the infectious-center assay and the primary-cell-culture assay, no virus was detected if cells had been killed by repeated freeze-thaw cycles prior to plating of the cells. 

^bThe infectious-center assay detects virus reactivation by culturing single-cell suspensions of lymphoid tissue with NIH 3T3 fibroblast monolayers over a 6-day period (7). 

^cLymphocyte suspensions were dispensed (1 × 10⁷ and 3 × 10⁶ cells) into six-well tissue culture plates in a final volume of 5.0 ml of medium. The primary cell cultures were incubated at 37°C and 5% CO₂ for up to 6 weeks, with 4.0 ml of supernatant being removed and replaced weekly with 4.0 ml of fresh medium (6). Culture supernatants were then assayed for the presence of lytic virus by plaque assay on NIH 3T3 cells (7).