A Peptide Fragment of β Cardiac Myosin Heavy Chain (β-CMHC) Can Provoke Autoimmune Myocarditis as well as the Corresponding a Cardiac Myosin Heavy Chain (α-CMHC) Fragment

The validity of the general belief that a cardiac myosin heavy chain (α-CMHC) is primarily responsible for causing experimental autoimmune myocarditis because of the more profound tolerance induction to β-CMHC due to its expression during the embryonic stage has been examined. In order to completely avoid cross-contamination among components of the two myosin heavy chains, recombinant myosin fragments were synthesized in Escherichia coli using cDNA fragments of rat a- and (J-CMHC cloned by reverse transcription polymerase chain reaction (RT-PCR). Two fragments corresponding to amino acid residues 1107-1164 derived from a-and β-heavy chains were equally capable of provoking severe myocarditis in Lewis rats when immunized in complete Freunďs adjuvant. No significant differences in the severity, as judged from histological scoring, were observed between the diseases induced by the two different peptide fragments, indicating conclusively that β-CMHC is as pathogenic as α-CMHC.