Rosette inhibition of antibodies depleted by absorption against NTS-DBL1α.
Immunoblotting (A) and rosette inhibition (B) by pairs of antibodies that were either non-absorbed, or absorbed on NTS-DBL1α recombinant protein coupled to sepharose. A) Recombinant NTS-DBL1α protein was spotted onto nitrocellulose membrane at doubling dilutions, starting from 2 µg/ml, and incubated with 1/1000 dilution of absorbed or non-absorbed antibody. 1) non-absorbed anti-NTS-DBL1α, 2) absorbed anti-NTS-DBL1α, 3) non-absorbed anti-NTS-DBL1α-CIDR1γ, 4) absorbed anti-NTS-DBL1α-CIDR1γ, 5) non-absorbed anti-DBL3ε, 6) absorbed anti-DBL3ε, 7) non-absorbed anti-DBL4δ and 8) absorbed anti-DBL4δ. Non-absorbed antibodies to DBLα (lanes 1 and 3) and DBL4δ (lane7) recognized NTS-DBL1α recombinant protein. After absorption, however, this activity was lost (lanes 2, 4 and 8). Antibodies to DBL3ε did not recognize NTS-DBL1α recombinant protein (lanes 4 and 5). B) Rosette inhibition assays showed that the anti-rosetting activity of NTS-DBL1α antibodies was lost after absorption. Antibodies to DBL3ε and DBL4δ retained rosette-inhibitory activity after absorption, showing that their anti-rosetting effects are likely to be independent of DBL1α. Antibodies to NTS-DBL1α-CIDR1γ also retained inhibitory effects after absorption on NTS-DBL1α protein, suggesting that antibodies to the CIDR1γ domain of ITvar9 also have anti-rosetting effects. Data shown are the mean and standard deviation of triplicate determinations of rosette frequency after overnight incubation with absorbed or non-absorbed antibody diluted 1/10 from the 1 mg/ml stock used for absorption. The control (with binding medium only added) had more than 50% of infected erythrocytes in rosettes.