Table 2.

Geometric mean serum IgG anti-LPS levels (ELISA units) after the third injection of S. dysenteriae type 1 conjugates into mice^*

Number of experiments	Immunogen	Carbohydrates/protein, mol/mol	IgG anti-LPS
3	Octamer–HSA	11	3.77
2	Octamer–HSA	20	11.1
4	Dodecamer–HSA	8	8.14
2	Dodecamer–HSA	10	9.52
2	Dodecamer–HSA	23	2.18
2	Hexadecamer–HSA	4	2.60
4	Hexadecamer–HSA	9	15.5
2	Hexadecamer–HSA	19	4.13
2	O-SP-HSA	N.A.	0.91

In 4 separate experiments, groups of 20 female 6-week-old general purpose mice from the NIH colony were injected s.c. with 2.5 μg of saccharide three times 2 weeks apart, and 10 from each group were exsanguinated 7 days after the second or third injections. Only the geometric mean IgG anti-LPS levels after the third injection of the conjugates are shown. Mice injected with saline or O-SP alone had no detectable antibody (data not shown). 11.1 vs. 3.77; P = 0.0003, 9.52, 8.14 vs. 2.18; P < 0.001; 15.5 vs. 2.60, 4.13; P = 0.0001; 15.5 vs. 8.14; P = 0.02, 15.5 vs. 9.52; NS. N.A., not applicable. 

^*Excluding the tetramer.