Meaning of "Antibody is 50% w/w pure of interfering proteins"

Question

From Google Patents, "Preparing antibodies from cho cell cultures for conjugation":

An isolated antibody or ADC is typically at least 50% w/w pure of interfering proteins and other contaminants arising from its production or purification but does not exclude the possibility that the monoclonal antibody is combined with an excess of pharmaceutical acceptable carrier(s) or other vehicle intended to facilitate its use. Sometimes monoclonal antibodies or ADCs are at least 60%, 70%, 80%, 90%, 95 or 99% w/w pure of interfering proteins and contaminants from production or purification.

Does it mean that even after purification the antibody solution may have an amount of impurities totaling to up to 50% of the antibody itself, in terms of weight? That the total weight of impurities may reach 50% of the antibody weight?

Maybe "an isolated antibody" is an antibody just after it has been produced? But the mention of "purification" confuses me. Why then such a high impurity content?

Answer 1

Patents are not the best source for reliable information, and obviously are not that readable. In this case they mean that of the purified product (usually that what comes of a protein A column I think), at least 50% of the weight is antibody. Or less (silly patents).

Commercial purification of antibodies (and proteins in general) is usually not that thorough. Most of the times what you'll get is just culture supernatant with cells removed, maybe some ammonium sulfate precipitation fraction or if it's thermostable just the proteins that are left after the production-solution is heated.