TABLE 3.

Existing antilisterial immunity does not alter the development of primary CTLs to L. monocytogenes-derived determinants

Expt	Immunizationa		Effector CTL frequencyb
	Primary	Secondary	LLO 91–99	p60 217–225	p60 449–457
A
	Wild type		1/21,840	1/90,800	1/226,000
	Wild type	Wild type	1/2,350	1/5,600	1/19,000
	p60 218F	Wild type	1/3,300	1/81,310	1/23,070
B
	Wild type		1/31,500	1/99,050	NDc
	92F	Wild type	1/32,900	1/62,460	ND
C
	Wild type		1/19,375	1/68,444	ND
	92F	Wild type	1/57,930	1/25,010	ND

^aBALB/c mice were immunized with the indicated strains, and 2 months later, they were injected with wild-type L. monocytogenes. Control animals were immunized with the wild-type strain at this time. Six days later, spleen cells were stimulated in culture, and the recovered cells were assessed for peptide-specific effector CTLs. 

^b51Cr-labeled RMAS-K^d cells were pulsed with a 10⁻⁹ M concentration of the indicated peptide for 60 min, and then they were added at 5 × 10³ cells/well. Serial dilutions of effector cells were added, and 4 to 6 h later, supernatant was collected for assay of ⁵¹Cr release. CTL frequency was determined as previously described (7). The data are representative of three experiments. 

^cND, not determined.