Most of our recombinant antibodies start with the immunization of rabbits as rabbit antibodies have desirable features including higher affinity and specificity when compared to mouse antibodies. After the rabbits develop an immune response, blood samples are taken, and the antigen-specific B cells are identified. These B cells are single-cell sorted into RT-PCR reactions to obtain the antibody variable domain genes. These genes are then expressed along with the antibody constant domains in mammalian cell culture to produce recombinant antibodies. The recombinant antibodies are screened for desired characteristics and the winning antibodies are then re-formatted into multiple scaffolds in order to increase the utility to our end users.
Our NullFc™ antibodies have genetically engineered Fc domains that contain point mutations that dramatically reduce binding to Fc receptors that are present on many cell types. This reduces background binding and produces cleaner, less-ambiguous results. NullFc™ also abolishes Fc effector functions such as ADCC. Our NullFc™ antibodies still retain the desired Fc features such as stability, long half-life and compatibility with traditional secondary detection reagents.
Rabbit PBMC’s were stained with either wild-type mouse IgG2a Fc domain or the same Fc domain but with NullFc™ modification. The significant binding of the wild-type mouse Fc to the rabbit cells is dramatically reduced with the NullFc™ modifications. In this experiment 35% background binding is reduced to less than 1.5% with NullFc™.
Since our antibodies are recombinant, they can be engineered with specific modifications which are not possible with traditional hybridoma methodology. One example of this is our antibodies that have site-specific biotinylation. We can engineer in a biotin acceptor peptide which results in biotinylation at a specific residue, and this site is typically placed far from the antigen binding domain so that every antibody retains full binding. We can control the exact location and number of biotins added to an antibody. This is in stark contrast to other vendors’ biotinylated antibodies which are typically randomly biotinylated and produce a heterogenous mixture of undefined antibodies containing an unknown number of randomly situated biotins. This can render many of the antibodies in the mixture as completely non-functional as the binding sites can be obscured or blocked by the random biotins. Our site-specific biotinylated antibodies produce 100% homogenous, fully functional antibodies with precise, defined biotinylation that also doesn’t change from lot-to-lot.
The good thing about science is that it’s true whether or not you believe in it.