Epitope peptide analysis by dot blot. The full length 18 meric peptide is designated as Ag0, the N-half 8 meric peptide is designated as Ag1 and the C-half 10 meric peptide is designated as Ag2. Monoclonal antibodies A, C, 6B8 and 3C4 are immunoreactive to the full length peptide but not either half peptide. The immunoglobulin contents are 9.8, 40.0, 7.7 and 15.0 μg/μL for clone A, C, 6B8 and 3C4, respectively, and were diluted 1:500 with 2% non-fat milk in PBS. Clone B, D, and 4H2 are not immunoreactive to any of these 3 peptides at up to 10 μg, data not shown.