Table 1.

Characterization of anti-mesothelin MAbs

MAbsIsotype*Affinity (nmol/L)FACSELISA§ (ng/mL)Western blot (ng)ImmunohistochemistryEpitope**
MNIgG2a1.03.51.12+1
MBIgG2a0.63.31.92+2
K1IgG1122.51,00025+1
5B2IgG1NA††1.31,00025+NA
  • * All MAbs contained a κ light chain.

  • Affinity to mesothelin-Fc in solution determined by BIACore.

  • Reactivity to H226 cells in FACS (log geometric mean of fluorescence intensity). Each MAb (1 μg/mL) was incubated with H226 (mesothelin-positive) cells and the bound MAb was detected by PE-labeled anti-mouse IgG. FACS histograms are shown in Fig 1. The values are geometric means of FACS signals. All the anti-mesothelin MAbs reacted to H226 cells.

  • § Reactivity to ELISA. ELISA plates were coated with mesothelin-Fc. After incubation with each MAbs, the bound MAb was detected by HRP-labeled anti-mouse IgG. The values are the amounts of MAbs that showed OD450 = 0.5.

  • Reactivity to SDS-denatured mesothelin-Fc in Western blot (Fig. 3). The values are the minimum amount of mesothelin-Fc from which each MAb can be detected with.

  • The results of K1 and 5B2 were cited from previous reports (2, 8, 9).

  • ** Topological group of epitopes identified based on the mutual competition of the MAbs (24).

  • †† Not applicable because 5B2 does not bind well to mesothelin-Fc.