Western blot analysis of A. actinomycetemcomitans serotype d LPS. LPS was isolated by hot phenol-water extraction from five clinical strains representing A. actinomycetemcomitans serotype d (lanes 1 to 5) and by hot phenol-water extraction and Sarkosyl extraction from one reference strain (lanes 6 and 7). Lane 1, strain 328; lane 2, strain 685; lane 3, strain 3033; lane 4, strain T-2222; lane 5, strain 508; lanes 6 and 7, reference strain IDH781. Isolated LPS preparations were subjected to SDS-12.5% PAGE, transferred on a nitrocellulose membrane, and treated with polyclonal antisera raised against A. actinomycetemcomitans serotypes a through e. The antigens were detected with rabbit antiserum raised against serotype d (a) or against serotype c (b).