Absence of specific antibodies to commensal coliphage by ELISA. (A) Fecal washes from 22 ICR mice found to be colonized with lactose fermenting commensal bacteria were assayed in duplicate for IgA antibodies against M13mp18, Lambda, P1, øX174, T4 and T7 coliphages in parallel ELISA plates. Mice 2B, 2R, 2G, 2N, 3G, 3R, 4N, and 6G were eventually shown to carry E. coli. Each symbol represents the mean absorbance reading for one phage type. (B) Sera from 9 mice verified as E. coli carriers were assayed in duplicate for IgG and IgM antibodies against the same six coliphage by ELISA. Each symbol represents the mean absorbance reading for one phage type.