I'm reading this paper https://www.ncbi.nlm.nih.gov/pmc/articles/PMC392475/ and I can't work out why a certain immune serum didn't work on the same viral protein but from different strains.
The serum was extracted from tumour-carrying animals infected with the 'SR' strain of Rous sarcoma virus and was later used to immunoprecipitate out the viral protein p60-src from virusinfected cells. The cells in question had been infected either with SR or other closely-related strains, all strains express the same protein. But the antiserum only extracted the SR strain's p60-src and not the same protein from other strains. I thought it could be because the serum had by chance targeted an epitope specific to the SR strain, so you get a lot of proliferation of B cells complimentary to this epitope, therefore overshadowing the detection of other epitopes. But 1. I think the serum was taken from multiple rabbits and surely they wouldn't all have happened to do this. and 2. a later paper I read said that p60-src is 98% the same across SR, Pr, Br strain etc so it seems unlikely to have latched onto an SR-specific bit. And yet, the authors state that due to similarities between SRC genes, "... similar gene products are probably present in cells transformed by other strains of ASV, but they are not detected because of a lack of crossreaction with the currently available antisera."
So my question is, what is causing this lack of crossreaction? Apologies if the answer is very obvious, I am new to the subject and have very little knowledge of experimental methods currently. Thank you in advance for any insights, or corrections on the conclusions I've drawn so far as they might be inaccurate too.
Note: thanks mods for letting me edit the question to improve privacy.