FIG. 4.

Competitive inhibition of the binding of rabbit anti-tD15 antiserum to tD15-coated microtiter wells by tD15 (▴), D15 peptides 4 to 8 (•) and 2 to 9 (○), or a mixture of irrelevant peptides (13 peptides derived from outer membrane protein P2 sequence) (▪). (A) Rabbit antiserum (2 μl) was adjusted to a concentration corresponding to 50% saturation of plate-bound tD15 and then preincubated for 1 h at room temperature with increasing amounts of either tD15, tD15 peptides 4 to 8, or a mixture of P2 peptides used as a negative control (total protein or total peptide concentration ranged from 10 ng ml⁻¹ to 20 μg ml⁻¹). Each point represents the mean of duplicate determinations for two rabbit immune sera tested individually. (B) Replotting of the data for tD15 peptides 4 to 8 from panel A in comparison with the result obtained with tD15 peptides 2 to 9. The concentration of each peptide in both mixtures (peptides 4 to 8 and 2 to 9) was adjusted to the same level (i.e., from 2 ng ml⁻¹ to 4 μg ml⁻¹).