Table 2.
Relative human FcγR binding measured by ELISA.
| FcγRI | FcγRIIa (H131) | FcγRIIa (R131) | FcγRIIb | FcγRIIIa(F158) | FcγRIIIa(V158) | |
|---|---|---|---|---|---|---|
| x-huCD20.IgG1 | ||||||
| mid-OD | 0.87 | 1.76 | 1.79 | 1.68 | 1.59 | 1.60 |
| ng/ml at mid-OD | 120 | 980 | 1700 | 3000 | 2300 | 670 |
| Relative binding | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
| x-huCD20.IgG4 (CHO) | ||||||
| Top OD | 0.06 | 2.86 | 3.29 | 2.20 | 0.12 | 0.18 |
| Relative binding | <0.02a | 0.071 | 0.20 | 0.17 | <0.02a | <0.003a |
| x-huCD20.IgG4 (Fut8KO) | ||||||
| Top OD | 0.15 | 2.75 | 3.29 | 2.69 | 1.46 | 1.99 |
| Relative binding | <0.04a | 0.069 | 0.28 | 0.21 | 0.076 | 0.045 |
Titration curves prepared in duplicate were assayed for receptor binding by ELISA as described in Methods and x-huCD20 antibody concentrations providing mid-OD were estimated using a 4 parameter fitting procedure. The relative binding was calculated as x-huCD20-IgG1 mid-OD concentration divided by the sample mid-OD concentration.
a
The top OD of the sample titration curve was much lower than the mid-OD for the x-huCD20-IgG1 control. To estimate the relative binding, the x-huCD20-IgG1 concentration corresponding to the top OD of the sample was calculated and divided by 500 ng/ml (for FcγRI binding) or 25000 ng/ml (for FcγRIII binding).