TABLE 3.

Effect of priming with homotypic pneumococci on standard middle ear challenge with histamine and Pn 14 (infection rate and immunologic parameters)

Infection rate or parameter	PBS (sham)	Pn 14	n (both groups)
Infection rate	73.9%	25.0%	24
Serum α Pn 14 IgG (days 28 and 33)a	0.0 ± 0.0	0.0 ± 0.0	18
Serum α CPS IgG (day 28)a	−0.03 ± 0.03	0.31 ± 0.10d	18
Serum α CPS IgG (day 33)a	−0.02 ± 0.07	0.58 ± 0.17d	18
IgA plasma cells/mm2 of mucosab	5.3 ± 0.2	12.9 ± 1.4d	3

^aDays 28 and 33 represent the change in value at the time of challenge and of section, respectively. IgG serum titers are the means of differences ± standard errors of the mean between the values before (day 0) and after priming (days 28 and 33); nonresponders are included. IgG titers are presented as log₁₀ dilution at 50% maximum optical density. 

^bFor IgA immunochemistry, bullae from three randomly chosen animals from each group were prepared on day 6 after challenge. 

^cSignificantly different (P < 0.05) from values in sham-treated groups as calculated by a Fisher's exact test. 

^dSignificantly different (P < 0.05) from values in sham-treated groups as calculated by a Student's t test.