Western blot analysis of the whole-cell proteins extracted from NTHi strains 12, 56, 72 and 91 probed with the 28D rabbit polyclonal antiserum (panel A), the 3D6 MAb (panel B) and the AD6 MAb (panel C). Whole-cell proteins were separated by SDS-PAGE and Western blot analysis was performed as described in Methods. Strain code numbers are indicated below lanes. M, Prestained SDS-PAGE standards (High Range). Arrows in panel A indicate the two HMW proteins of strains 12 and 56 recognized by the 28D polyclonal antiserum, that reacted with a single band in strain 91 and no band in strain 72.