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antibody production-how to differentiate epitope as foreign


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#1 bruceli

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Posted 31 January 2011 - 07:56 AM

Hey guys,

I'm using a polyclonal antibody targeting an intracellular sequence of one cell surface protein, and the rabbit producing this polyclonal antibody expresses this membrane protein with exactly the same sequence as the epitope injected. How could that happen? How did the host animals recognize the injected peptide as "foreign" if they have the same sequence? Second, isn't the antibody gonna make the rabbit sick or have some autoimmune phenotype once made? (p.s. synthetic epitope: 18 amino acids) Thanks a lot!

BL

#2 Chelo

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Posted 31 January 2011 - 08:58 AM

Hi,

some time ago, I had exactly the same question for mouse antibody production. The answer seems to be that although in principle there should be no response against self-antigens, the tolerance depends on the way the antigen is presented (subcutaneously, intraperitoneally, etc.). In addition, the adjuvant plays an important role in immune system activation. And finally, yes, the antibodies you are producing can be detrimental for the rabbit.

#3 bruceli

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Posted 31 January 2011 - 12:17 PM

Thanks Chelo. It really helps!

Hi,

some time ago, I had exactly the same question for mouse antibody production. The answer seems to be that although in principle there should be no response against self-antigens, the tolerance depends on the way the antigen is presented (subcutaneously, intraperitoneally, etc.). In addition, the adjuvant plays an important role in immune system activation. And finally, yes, the antibodies you are producing can be detrimental for the rabbit.



#4 BioMiha

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Posted 31 January 2011 - 12:20 PM

Hi,
Self vs. foreign is a gross oversimplification of the immune system. The fact is that the immune system only rejects certain autoreactive antibodies, that react to antigens expressed in the bone marrow. For the majority of other self antigens that are found in the periphery the immune system deletes autoreactive clones because there is an absence of additional activational signals associated with pathogens (which are for the purpose of immunisation usually provided by ajuvants). So in essence the immune system differentiates between self and non-self because self is not associated with danger signals. If however, a self antigen is associated with danger signals = immunisation in the presence of adjuvants (most often killed mycobacteria), it mounts an immune response. Therefore the rabbit makes antibodies to the antigen.
But even more importantly in your case I imagine that the rabbit was immunized with some sort of peptide. Even though this peptide might correspond to an amino acid sequence encountered in the rabbit itself, the conformation of the peptide is very different when it is bound to the carrier molecule as compared to when it is part of the protein. I myself think immunization using peptides is more often than not a waste of time, because the immune response is more often than not directed to the free ends of the peptides and the antibodies that are generated usually do not cross react with the intact antigen.

#5 bruceli

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Posted 01 February 2011 - 08:21 AM

Awesome. Thanks a lot, friend!

Hi,
Self vs. foreign is a gross oversimplification of the immune system. The fact is that the immune system only rejects certain autoreactive antibodies, that react to antigens expressed in the bone marrow. For the majority of other self antigens that are found in the periphery the immune system deletes autoreactive clones because there is an absence of additional activational signals associated with pathogens (which are for the purpose of immunisation usually provided by ajuvants). So in essence the immune system differentiates between self and non-self because self is not associated with danger signals. If however, a self antigen is associated with danger signals = immunisation in the presence of adjuvants (most often killed mycobacteria), it mounts an immune response. Therefore the rabbit makes antibodies to the antigen.
But even more importantly in your case I imagine that the rabbit was immunized with some sort of peptide. Even though this peptide might correspond to an amino acid sequence encountered in the rabbit itself, the conformation of the peptide is very different when it is bound to the carrier molecule as compared to when it is part of the protein. I myself think immunization using peptides is more often than not a waste of time, because the immune response is more often than not directed to the free ends of the peptides and the antibodies that are generated usually do not cross react with the intact antigen.






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