Western immunoblotting analysis of P65 in wild-type (WT) M. pneumoniae and noncytadhering mutants I-2, II-3, II-7, III-4, IV-22, and M6, as indicated (50 μg of protein per lane). Anti-P65 serum was used at a dilution of 1:7,500. The position of the 66-kDa protein size standard is shown on the left.