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Antibodies that give you both high affinity and high specificity thanks to our RabMAb® technology.
Most monoclonal antibodies are typically produced in mice, yet their antibody-producing B cells are unable to generate every kind of antibody required. To overcome the limitations of mouse B cells, we developed a unique method of monoclonal antibody development using rabbits: the RabMAb® platform.
Compared with other species, such as mouse, rat, and chicken, the rabbit has a unique immune system. Rabbits have a large B-cell repertoire, which means they generate a very diverse range of antibodies. The rabbit immune system optimizes affinity by mechanisms that are more efficient than those of mice and other rodents. We can use rabbits to produce these high-affinity antibodies, even against antigens that are not immunogenic in mice. On average, rabbit monoclonal antibodies have 10–100 times higher affinity for a target antigen than mouse monoclonal antibodies.
Rabbit antibodies are also better at distinguishing subtle differences. such as epitope variations like modifications, mutations, and conformational changes, due to the larger and more diverse B-cell repertoire. RabMAb® primary antibodies combine the best properties of monoclonal antibodies with the most desirable attributes of rabbit polyclonal antibodies:
Some of the most popular RabMAb® primary antibodies include
As monoclonals, RabMAb® primary antibodies detect a single epitope so are less likely to cross-react with other proteins. At the same time, we have observed that RabMAb® primary antibodies bind to their target with greater affinity enabling higher signal-to-noise ratio than mouse mAbs at a given concentration of antibody.1 The benefit of this is that RabMAb® primary antibodies typically provide more specific and sensitive detection of their target protein with low background.
Figure 1. A) C-myc – IHC on FFPE human colonic adenocarcinoma using anti-c-Myc RabMAb® primary antibody (ab32072). B) AMPK alpha 1 (phospho S496) – IF on HeLa cells using anti-Phospho-AMPK alpha 1 (pS496) RabMAb® primary antibody (ab92701).
While mouse monoclonal antibodies can also be highly specific, subtle changes in epitopes are often not recognizable by the mouse immune system while the rabbit immune system can. This enables the generation of highly specific antibodies, even to specific cleaved versions of a protein.
Figure 2. A comparison of multiple PARP RabMAb® primary antibodies. Each Poly (ADP-ribose) polymerase (PARP-1) specific antibody specifically recognizes specific cleavage sites with no cross-reactivity to non-specific cleavage sites.
In terms of your experiment, a high affinity means that you can use more stringent conditions without worrying about the loss of signal strength, therefore ensuring the cleanest results with the highest possible specificity.
Antibody affinity is typically represented by the equilibrium dissociation constant (KD), a ratio of koff/kon between the antibody and its antigen, where lower KD value suggests higher affinity relationship.2 While most therapeutic monoclonal antibodies have a KD value in the nanomolar range (KD = 10-9 M), rabbit monoclonals consistently demonstrate higher affinity, with the KD values which can often reach the picomolar level (KD = 10-12 M), effectively eliminating the need for further affinity maturation.3
Table 1. Affinity comparison by KD value for antibodies generated with RabMAb® primary antibodies vs popular therapeutic antibodies.
1.28 x 10-12
5.0 x 10-9
2.82 x 10-12
8.0 x 10-9
9.57 x 10-11
1.0 x 10-9
1.25 x 10-11
2.0 x 10-10
1.99 x 10-10
5.0 x 10-10
RabMAb® primary antibodies offer increased sensitivity with no loss of specificity, making them ideal for demanding applications like immunohistochemistry (IHC) on formalin-fixed paraffin-embedded FFPE tissues.
RabMAb® rabbit monoclonal antibodies permit higher working dilutions (5–10X on average) and are compatible with various tissue fixation processes. We always test RabMAb® antibodies on human lymphoid/lymphoma tissue microarray (TMA) constructed with FFPE tissues for immunohistochemical staining.
Figure 3. A comparison of leading NeuN antibodies on acetone-fixed adult mouse dentate gyrus frozen sections. A) Leading mouse monoclonal, 1/200 dilution, shows background that cannot be reduced by antibody dilution. B) Anti-Neun-antibody [ERP12763] (ab177487), 1/4000 dilution, shows specific staining with minimal background.
Rabbits have a unique immune system which allows them to develop antibodies against small epitopes present in small molecules, lipids, and polymers or subtle changes in epitopes such as post-translational modifications or single amino acid substitutions. RabMAb® primary antibodies offer high affinity and specificity to the modified target with minimal cross-reactivity to the non-modified site.
The ability of rabbit antibodies to recognize small epitopes translates to success with recognition of post-translational modifications (eg phosphorylation, methylation, acetylation, sumoylation). In addition, many small compounds and peptides do not elicit a good immune response in mice but do so in rabbits.
Figure 4. RabMAb® primary antibodies detecting specific phospho sites. A) phosphotyrosine (pY): ab68470. B) Phosphoserine (pS) (ab81292) C) Phosphothreonine (pT) (ab81551). D. Dual Phospho (pT/pS) (ab32525).
Every RabMAb® primary antibody is validated in an average of three recommended applications prior to release. For IHC, all RabMAb® primary antibodies are tested on formalin-fixed and paraffin-embedded (FFPE) human tissue array for more accurate verification of antibody sensitivity and localization.
Figure 5. Validation results for Caspase-3 (Pro) RabMAb® primary antibody (ab32150) on A) western blot on HeLa cell lysate, B) IHC on FFPE human cervical carcinoma tissue, C) flow cytometry on Jurkat cells, and D) ICC on HeLa cells.
1. Rossi S et al. Am J Clin Pathol. 2005 Aug;124(2):295-302 (2005)
2. King DJ. Applications And Engineering Of Monoclonal Antibodies (2007)
3. Pop ME. J Immunol Methods 28;341(1-2):86-96 (2009)