Preparation of latex sensitized with rabbit IgG antibody for slide reversed passive agglutination

A method is described for preparing latex particles sensitized with IgG antibody (IgG-sensitized latex) applicable to the slide reversed passive agglutination (RPLA) test. Soap-free latex (latex) was sensitized with IgG which had been isolated from rabbit anti-bovine lactoferrin serum using protein A Sepharose CL 4B. Unadsorbed protein-binding sites on the surface of latex were blocked with bovine serum albumin (BSA). IgG-sensitized latex that gave better agglutination in RPLA could be selectively obtained by centrifugation at 19 900g for 15 min in 0.01 mol/L glycine buffer (pH 7.3; specific gravity 1.042) containing 3% NaCl, 5% saccharose and 2% choline chloride. By dispersing this IgG-sensitized latex in 0.01 mol/L glycine buffer (pH 7.3) containing 1-2% BSA, a uniformly suspended, highly reactive, readily agglutinable preparation was obtained.