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Subclasses of rat immunoglobulines


Rat is often considered as a pest but yet few people really know him. Rat is one of the predominant animal hosts for monoclonal antibody production, second to its rodent brother, mouse, and followed by rabbit.


The term 'rat' encompasses multiple species, including the famous species Norway rat (Rattus norvegicus), and black rat (Rattus rattus). In the 80’s, Pr. Bazin developed a unique species called Rat-LOU in Louvain-La-Neuve laboratories in Belgium. In fact, this particular rat species has been called after the city name. Each time a clone name starts with “LO”, you can be 100% sure it’s a rat monoclonal antibody coming from SYnAbs company.


Same as human and mouse, rat has five antibody isotypes (IgA, IgD, IgE, IgG, and IgM). But in mice the IgG class is divided into five sub-classes (IgG1, IgG2A, IgG2B, IgG2C and IgG3) whereas in rat there are only four (IgG1, IgG2A, IgG2B, IgG2C).




































Why using rat monoclonal antibodies?


Each time, you work with mouse species for preclinical experiment or R&D tests, a secondary antibody of a different species will get you a better recognition of your primary antibody. In fact, mouse antibodies are seldom used to produce antibodies against mouse antigens due to their tolerance of syngeneic antigens. Rats can so provide a large number of spleen B cells that are available for fusion with myeloma cells, which are extremely suitable for generating mAbs against mouse antigens. 


This is why SYnAbs developed a panel of rat secondary monoclonal antibodies targeting the entire repertoire of mouse isotypes.


Rat antibodies against any animal species


SYnAbs has developed rat monoclonal antibodies against isotypes of llama (anti-VHH), rabbit, dog, cow, pig, and human to cover a large spectrum of species.


What are the advantages of rat monoclonals?



  • In addition, the rat antibodies are found do not have the cross reaction in immune-detection of antigens out of a mouse background, which shown as a strong point in sandwich immunoassays.
  • Rat require reduced antigen amount for immunization, potentially saving costly raw material.
  • No special growth media is required: you can keep everything intact compared to mouse hybridoma cells without additional costs.
  • As a larger animal, rat will permit you to get access to lymph nodes organs, with a different immune response. In order to do so, you need to perform footpad immunization.


Can I generate a hybridoma of rat with mouse myeloma?


In general, hybridoma is a difficult method to develop monoclonal rat antibody due to the lack of stable fusion partner. To our knowledge, all ratXmouse hybridoma clones grow slowly and will be gradually lost during the clonal selection step due to their genetic instability.



At SYnAbs, our scientists has developed IR983 the rat myeloma cell line coming from rat-LOU species. For each fusion, we’re ensuring a ratXrat homo-hybridoma clone with high productivity and stability features.


Can I purify rat monoclonal antibody with classical protein A?


It’s not possible to purify rat monoclonal antibody with classical protein A capture step. The flip side of the coin is that SYnabs has been able to develop a rat antibody that specifically recognize protein A. This tool is used by our CDMO partners who want to discriminate free protein A and protein A linked to the purified antibody.



As an alternative, you can use protein G or protein L but if you perform your culture in serum conditions there’s a notable risk you bind bovine antibodies present into the serum. The best solution is to perform immunoaffinity capture step, using MARK reference for instance, a secondary antibody of mouse targeting all rat isotypes.