If the protein epitope that is recognized by the antibody correlates with the homology region of the gene, it should work, because the Ab recognize the same aminoacid sequence (and even better if it is a polyclonal Ab).

Keep us posted, Good luck

Homology of the epitope is more critial than sequence homology. If you have an idea where the target epitope is, perform a protein-protein BLAST to find other possible targets. To add another layer of complexity, epitopes with comparable homology on different proteins might / might not be recognized by an antibody depending on the local hydrophobicity and accessibility of the epitope.

I cannot suggest you at this point as I do not know your work plan. But it is possible to raise antibody in rat against C9 in the laboratory. You can use Hapten if necessary. Pierce and may other good companies will help you in that. If you use synthetic rec. source of antibody you can talk with SantaCruz. All I am referring in USA. But you will find very good companies in your home country too. Hope these will help you.

Maybe. Examine the peptides antigenic epitopes to decide. To do this run the peptide sequence in something like gene runner (freeware). If the antigenic sites look good and they have high surface probability it may work.

Hi,

I am wondering whether you did check other species than human ? For instance, an antibody against porcine complement protein C may have a higher homology.

Best regards & have a nice weekend !

Andrea

Antibodies recognize peptide epitopes, which are generally 6 amino acids long. 3 distinct antibodies can be identified when using a 9 amino acid antigen. If there are conserved, consecutive 6 amino acid sequences within the 70% sequence homology domains, then there is a strong possibility that polyclonal antibodies raised against the human peptide antigen will recognize the same peptide from rat. That said, post-translational modifications of these epitopes in the endogenous protein, and particularly differences in modification between human and rat, make a simple epitope comparison insufficient. As already mentioned, contacting the supplier may answer your question. Most of the larger companies choose conserved antigens and have tested the antibodies against other species.

I agree with Francisco, you stand a much better chance with a polyclonal vs a monoclonal antibody. Unfortunately the only way to find out is to do the experiment. Call the company and see if they will let you have a sample to test, and be willing to share the data with them.

We make antibodies for projects and would not set out with a peptide with only 70% homology. However, If you immunise a good number of rabbits you will probably get one that cross reacts, but you might not! We have raised an antibody against an isoform that differed by a single amino acid (actually a single CH3 group) so it is possible to get a number of different selectivities out of an immunogen, some of them will cross react with everything, other will be very selective.

Good luck......

This may be outside the intended use, but perhaps an anti rat C9 neoeptiope mAb could be of use? Are you perhaps trying to detect the deposition of rat C9 or MAC complex (C5b-9) in tissue? The mAb 2A1 (mouse anti rat C5b-9) works fine in histology, FACS, ELISA. Also pierce seems to sell an antibody (Rabbit pAb, PA5-29093) which cross reacts between human and mouse, which would give a good chance of cross-reacting with rat as well?

Good luck!

-Juha

Hi Ned J Lamb, do you have any useful references that indicates the % identity needed for cross reactivity?