Your Outsourcing Partner for Protein Research and Production Services

To meet the needs of our clients, Exon BioSystems provides protein characterization of our expressed protein to insure the quality of recombinant protein.

Recombinant Protein Expression

Exon BioSystems is a protein contract research and production services company specializing in recombinant protein expression, protein purification, and protein characterization.

Antibody Engineering

Additional areas of expertise include assay development of G-protein coupled receptor, recombinant vaccine development and recombinant antibody production.


Exon BioSystems is a protein contract research and production services company specializing in recombinant protein expression, protein purification, and protein characterization.


Rabbit Monoclonal Antibodies

exonbio offers custom Rabbit Monoclonal Antibody development services using SPIN® (Single Plasma Cell Interrogation) Technology. This proprietary technology screens the immune repertoire of rabbits, creating the power to select desired rare antibodies directly from affinity matured plasma cells.

The Advantage of SPIN® Technology

SPIN® Technology RabMab® /Hybridoma B Cell
Display Technology Single B
Cell Cloning
Start Material Plasma Cells B Cells B Cells B Cells B Cells
Chain Pairing Native Native Native Mixed Native
Timeline 1 Month 4-5 Months 3 Months 2 months 2 months
Diversity High Medium Medium Low Medium

* Timeline from sacrificing immunized animal to identifying clones, phase II-Phase IV:

  • High affinity: Only high affinity antibodies will be selected owing to the isolation of the terminal differentiated plasma cells.
  • Broad spectrum of epitope coverage: We take advantage of the unique properties of the rabbit immune system to obtain antibodies against a broad spectrum of epitopes for a single antigen.
  • Recombinant antibodies ensure the preservation of genetic information.
  • The customer will receive both monoclonal and polyclonal end products.


The Benefit of Rabbit Monoclonal Antibody

Rabbits are well-known for mounting a strong immune response against foreign antigens and rabbit polyclonal antibodies are among the first established and most widely used research tools in immunology, Rabbits produce better antibodies to many antigens than rodents in terms of affinity and specificity.

  • Higher affinity and specificity
  • Antibody affinity is typically represented by the equilibrium dissociation constant (KD), a ratio of koff/kon between the antibody and its antigen. While most mouse monoclonal monoclonal antibodies have a KD value in the nanomolar range (KD = 10-9 M), rabbit monoclonals consistently demonstrate Kd values that can reach the picomolar level (KD = 10-12 M).

    In an immunoassay, a high affinity means that you can use less antibody under more stringent conditions without a corresponding loss of signal strength, therefore ensuring the highest sensitivity with the highest possible specificity.

  • More diverse epitope recognition
  • The lower immune dominance, extensive somatic gene conversion, and hypermutation that characterizes the rabbit immune response results in a more diverse epitope recognition. Thus, the rabbit immune system will yield a wider range of antibodies, recognizing more unique epitopes.

  • Improved immune response to small-size epitopes
  • Rabbits have a unique immune system that allows them to develop antibodies against small moieties in small molecules, lipids, and polymers, or subtle changes in epitopes such as post-translational modifications or single amino acid substitutions. The ability of rabbit antibodies to recognize and mount an immune response to tiny differences is revealed by the large numbers of antibodies that target post-translational modifications (e.g. phosphorylation, methylation, acetylation).

Comparison of Rabbit and Mouse Monoclonal Antibodies

mouse Rabbit
Antigen recognition Limited response to small molecules and peptides
Narrow spectrum of epitope recognition
No response to rodent antigens
High response to small molecules and peptides Recognize more epitopes per protein
Affinity Nanomolar (10-9M) Picomolar (10-12M)
Quality Often not good for IHC, ICC Excellent for IHC and ICC

Why the Rabbit is a Superior Animal for Antibody Development

B cell development and repertoire diversification vary significantly among species. Diversification of the Immunoglobulin (Ig) repertoire occurs through the combinatorial joining of multiple V (for "variable"), D (divergent), and J (joining) gene segments for the Ig heavy and light chains through VDJ Rearrangement, followed by somatic mutagenesis upon subsequent B-cells exposure to a foreign antigen (Somatic Hypermutation). Compared to humans and mice, which use a diverse assortment of germline VH gene segments during VDJ rearrangement of the heavy chain, the rabbit IgH repertoire displays highly restricted VH gene segment usage.

The rabbit and chicken immune system generates antibody diversity and optimizes affinity by mechanisms that are more efficient than those of mice and other rodents. Besides the common Somatic Hypermutation, Rabbit and chicken B cells also employ a mechanism called Gene Conversion, which involves the non-reciprocal homologous recombination of upstream pseudo V gene loci into the recombined VDJ (and VJ) locus. The gene conversion using approximately 300 pseudo V-genes dramatically enhances the diversity of rabbit antibody repertoire and increases the probability of generating functional antibody clones.


Christoph Rader, The Scripps Research Institute. From rabbit antibody repertoires to rabbit monoclonal antibodies Experimental & Molecular Medicine 2017 49:e305

Masatoshi Nei, Penn State University Fifty-million-year-old polymorphism at an immunoglobulin variable region gene locus in the rabbit evolutionary lineage Proc. Natl. Acad. Sci. USA 1999 96:9710-9715

Patented SPIN® Technology

The success of single memory cell based monoclonal antibody technology used in generating HIV neutralization antibodies, inspired us to develop a single plasma cell based approach to develop monoclonal antibodies. Plasma cells and memory cells are the two types of terminally differentiated cells harboring fully matured antibody clones. For both humans and mouse, there are already known cell surface markers available for memory cells and plasma cells. However, in order to isolate plasma cells from other common (and superior) antibody generating animals, such as rabbit, chicken, and llama, we developed a patented new approach that is capable of isolating plasma cells from these species with high accuracy.

The Benefits of the Rabbit Immune System and SPIN® Technology

The nature of the rabbit immune system generates broader antibodies with higher affinities. Current hybridoma technology and phage display technology can't effectively screen for the best antibodies from the large amount of low affinity or non-specific clones. Our new Single Plasma Cell Interrogation (SPINĀ®) technology can retrieve the rare and superior clones from among millions of B cell clones.