Purity: Based on immunoelectrophoresis at an antigen concentration of 20 mg/ml, the pattern of precipitation against goat anti-human whole serum is the same as that against goat anti-human IgM, Fc5m fragment specific. No precipitin line was detected against goat anti-human IgG, Fc fragment specific; goat anti-human IgA, a chain specific; or goat anti-humanalpha-2 macroglobulin.