IgG induced by DBL4e immunizations reacted with the DBL4e peptides and no reactivity was detected with IgG from control IgG (data not shown). The overall level of reactivity was lower in rabbit serum (n = 4) compared to rat serum (n = 10) and a lower proportion of the rabbits reacted with a given peptide (data not shown). In general, the same areas of the linear sequence were targeted by IgG from the rats and rabbits, with the most distinct reactivity in both species of animals observed against peptide 2 to 5 ( Figure 5A ). However, it appeared that the rat antibody reactivity was skewed one to three peptides N-terminally compared to rabbit antibodies. Hence, the major peaks of reactivity recognized by rabbit-antibodies were peptides: 1-5, 14-19, 21-28, 31-33, 35-36 & 58-61, whereas rats recognized peptides 2-6, 14-20, 22-26, 31-38 & 60-63. Other peptides in the array were recognized by one species only, albeit some of them with quite low OD values. The major peak of reactivity (peptides 3-6) recognized by both rabbit-antibodies and rat-antibodies and one minor peak with distinct skewed reactivity (peptides [33] [34] [35] [36] [37] [38] were mapped on the structure model ( Figure 5B ). Both these areas of the model were predicted to contain unstructured loops. In addition, peptide 3-6 contained a b-sheet hairpin motif and peptide 33-38 contained several a-helixes. The other minor peak primarily targeted by rat antibodies (peptides 61-62) was also characterized by unstructured amino acid sequences (data not shown). In summary, the average reactivity to linear peptides covering the amino acid sequence of DBL4e was, apparently slightly skewed, but otherwise remarkably similar between rabbits and rats.