Characterization of 1E4 by ELISA and Western blotting. Panel A, isotyping of 1E4 by ELISA with PI antigen. A 96-well microtiter plate was coated with inactivated PI or PII antigen and incubated with the hybridoma supernatant from cloned hybridoma 1E4. The reactivity of 1E4 with anti-IgM, -IgG, -IgG1, -IgG2a -IgG2b and -IgG3 was measured by OD 490. The values represent the average absorbance at 490 nm of duplicate wells. Panel B, the reactivity of 1E4 with PI and PII antigens, and proteinase K digested PI and PII antigens in Western blotting. I: PI antigen; I/PK, proteinase K-treated PI antigen; II: PII antigen; II/PK, proteinase K-treated PII antigen.