Isolated fab fragments can be used to bind antigen to antibody in solution or on the cell surface without causing the undesired complications of cross-linking and precipitation, or patching and capping, respectively. No reaction by IEP to antisera to human IgG-fc. Prepared from plasma shown to be non reactive for HbsAG, anti-HCV, anti-HBc, and negative for anti-HIV 1 & 2 by FDA approved tests. >95percent pure by SDS-PAGE.