TABLE 3.

Passive immunization of naive mice with PspA immune serum from pJB100-immunized mice^a

Antigen	Serum dilution	Alive/dead mouse ratio
pJB100	1:2	4:0
	1:20	4:0
	1:200	1:3
PspA	1:2	4:0
	1:20	2:2
	1:200	0:4
LR solution		0:4

^aNaive CBA/N mice received intraperitoneal injections of pooled immune serum from mice immunized with pJB100 or PspA. Mice were challenged i.v. with pneumococcal strain WU2 1 h after receiving the pooled serum. The PspA immune serum was diluted to a concentration equivalent to that of the pJB100 immune serum (8 μg of antigen-specific antibody/ml) prior to preparation of serial dilutions for passive immunization.