Strategy overview. A: Enrichments of a naïve yeast-display scFv library by (1) 2 magnetic sortings and (2) 3 flow sortings for the scFv that bound to 100 μg/ml of biotinylated case-pool serum. B: Depletions of the enriched sub-library by two magnetic depletions for the scFv that bound to 50 μg/ml of biotinylated control-pool serum. C: Enrichments for yeast that displayed scFv binding to 100 μg/ml of biotinylated case-pool serum, or that expressed c-myc tagged scFv. D: PCR amplification of case-pool serum-specific recognition sequences and cloning by gap repair in pTOR2 vector. E: High-throughput mating of yeast secreting scFv with yeast transformed with pTOR BIR to produce diploids that secrete biotinylated scFv, biobodies (Bbs). F: Immunoprecipitation of serum proteins with case-pool serum-specific biobodies and magnetic elution of immunoprecipitated case-pool specific serum proteins. G: Tryptic digestions in-solution or after in-gel separations of immunoprecipitated proteins. H: Mass spectrometry data acquisition and analysis.