MOLECULAR MIMICRY - HISTONE H3 AND MYCOBACTERIAL PROTEIN EPITOPES

A 15-kDa protein detected initially in amyloidotic ileum from a transg enic mouse and subsequently in control (nontransgenic) ileum by variou s polyclonal rabbit antiserums applied to electroblots of extracts der ived from these tissues was identified by partial sequence analysis as histone H3. Antiserums were made against immunogens unrelated to the histone, but they recognized calf thymus histone H3 (14.7 kDa) on West ern blots. The bacterial component of the Freund's medium used as an a djuvant for the immunogens was either Mycobacterium butyricum or Mycob acterium smegmatis. Absorption tests with histone H3 and sonicated M. butyricum substantiated the presence of anti-histone H3 activity in th e antiserums. These findings indicate that the two mycobacterium speci es make a protein with epitopes perceived as nonself by recipient rabb its but sufficiently similar to epitopes of mammalian histone H3 that the rabbits produced antibodies cross-reactive with the histone.