[Immune reactions in pseudo-lupus-syndrome. A long-term study (author's transl)]

Anti-mitochondrial antibodies in patients with dilated cardiomyopathy (anti-M7) are directed against flavoenzymes with covalently bound FAD

Anti-mitochondrial antibodies (anti-M7) in sera from patients with dilated cardiomyopathy and myocarditis recognize, besides mitochondrial antigens, bacterial sarcosine dehydrogenase. The common target antigen was identified as the covalently bound FAD of mitochondrial and bacterial flavoenzymes. Thus, anti-M7-positive serum reacted on Western blots exclusively with covalently flavinylated enzymes. The antigenic specificity of anti-M7 sera was reproduced by an antiserum raised in rabbits with 6-hydroxy-D-nicotine oxidase. The heart mitochondrial membrane antigen recognized by anti-M7 serum was identified as the flavoprotein subunit of succinate dehydrogenase, the antigens in rat liver mitochondrial matrix as the flavoenzymes dimethylglycine dehydrogenase and sarcosine dehydrogenase. Anti-M7 serum contained a specific anti-flavoenzyme antibody fraction. Nanomolar concentrations of FAD and riboflavin inhibited the immune reaction on Western blots and in ELISA, and incubation with FAD-agarose depleted the anti-M7 activity of the serum. N-terminally deleted dimethylglycine dehydrogenase proteins were only immunoprecipitated by anti-M7 sera when the FAD was covalently incorporated. An affinity constant (KD) of 10(-8) M was established for the anti-flavoenzyme antibodies by competitive ELISA. Of patients with cardiomyopathy and myocarditis, 36% and 25%, respectively, were anti-flavoenzyme-positive by Western blot and ELISA, but only two of 15 patients with other heart diseases and none of 50 healthy controls.

Mitochondrial antigen/antibody systems in primary biliary cirrhosis: revisited

Methods for the evaluation of the four antimitochondrial antibody subtypes in primary biliary cirrhosis - anti-M2, -M4, -M8, -M9 - are described. The importance of the application of different preparations for the demonstration of complement fixing antibodies and the detection of antibodies by ELISA or Western blotting is emphasized. Complement fixing antigens can be prepared by discontinuous isopynic sucrose density gradient centrifugation using mitochondrial subfractions derived with from beef heart (M2), rat liver (M4), or pig kidney (M8). Anti-M9 antibodies do not fix complement. For ELISA, the pyruvate dehydrogenase or the ATPase-associated antigen fraction (M2), the sulfite oxidase fraction (M4), and the chromatographically purified M8-fraction should be used. The same antigen fractions are suitable for Western blotting, but anti-M4 and anti-M8 by ELISA and Western blotting a purified fraction prepared from rat liver has to be applied. Correlating antimitochondrial antibody-subtypes with clinical condition and the natural course, there is convincing evidence that especially the presence of complement fixing antibodies against the subtypes M2, M4, and M8 is a reliable indicator for a more active course. Patients expressing only anti-M9 (without anti-M2) have biochemically all the typical features also found in classical anti-M2 positive primary biliary cirrhosis patients, but seem not to advance to late stages. Since these antimitochondrial antibody-subtypes are present even in very early stages stages without changing their pattern during the course, antimitochondrial antibody-profiles can also be taken as early prognostic parameters. The evaluation of the immunological activity by antimitochondrial antibody-subtype testing may further facilitate the decision whether therapy with ursodeoxycholic acid should be combined with steroids and/or immunosuppressive agents. The role of mitochondrial autoantigens in the induction of this chronic destructive bile duct process is also discussed. The concept is put forward that not bile ducts but naive(?) B-cells expose the different mitochondrial antigens, thereby stimulating autoreactive T-cells to provide a second signal for antibody production. The degree of breakage of tolerance to the different mitochondrial epitopes may be one crucial factor which determines the diversity of antimitochondrial antibody-subtypes in patients with primary biliary cirrhosis.

The specificity of the lymphocyte transformation test in a patient with hypersensitivity reactions to pyrazolone compounds. A 10-week follow-up study before and after rechallenge

To evaluate the specificity of the lymphocyte transformation test (LTT) in the diagnosis of drug allergy we studied over 71 days an atopic woman with a past history of frequent adverse reactions to pyrazolone drugs. Rechallenge with the incriminated substances aminophenazone (aminopyrine) and propyphenazone was carried out on Days 11 and 31 respectively. An immediate type of hypersensitivity reaction was seen after 100 mg aminophenazone, while 100 mg of propyphanozone led to a serum sickness-like syndrome. We found two specifically sensitized lymphocyte populations using either the pure substance or sera containing metabolite in cell cultures. Stimulatory responses with indices ranging between 3 and 6 were seen 3-4 days after exposure, and the tests remained positive in both instances for 3-4 weeks. Specific sensitization was proven by positive skin tests and by a small but distinct lymphocyte proliferative response before challenge. Several lymphocyte function tests were performed over a period of 53 days and revealed a large fall in pokeweed mitogen-induced immunoglobulin synthesis and an increase in suppressor cell activity after rechallenge with aminophenazone. We conclude that the proliferative response observed in the presence of the offending drug is due to the activation of T memory cells and therefore highly suggestive of a true allergic reaction.

Mitochondrial antigens and autoantibodies: from anti-M1 to anti-M9

The specificity and clinical relevance of nine antimitochondrial antibodies (AMA) - anti-M1 to anti-M9 - are described. All nine AMA types react with antigens which are associated either with inner (M1, M2, M7) our outer mitochondrial membranes (M3, M4, M5, M6, M8, M9) derived from rat liver or beef heart mitochondria. These antigens can be clearly distinguished by their different physical and chemical properties. Anti-M1 to anti-M9 can be related to distinct clinical entities: anti-M1, anti-M5, and anti-M7 are found in nonhepatic disorders, such as syphilis (anti-M1), undefined collagen diseases (anti-M5), and some forms of cardiac diseases (anti-M7). Anti-M3 and anti-M6 are detected in drug-induced disorders, such as phenopyrazon-induced pseudolupus syndrome (PLE; anti-M3) and iproniazid-induced hepatitis (anti-M6). Anti-M2, anti-M4, anti-M8, and anti-M9 are confined to primary biliary cirrhosis (PBC). Anti-M2 is a specific marker for the diagnosis of PBC; 96% of PBC patients (n = 752) were anti-M2 positive. Anti-M4 and anti-M8 seem to reflect disease activity. Anti-M9 antibodies occur preferentially in early PBC. The clinical course of PBC was analyzed with respect to four different AMA profiles: profile A: only anti-M9 positive in the ELISA; profile B: anti-M9 and anti-M2 positive in the ELISA; profile C: anti-M2 positive in ELISA and complement fixation test (CFT), but anti-M4 and anti-M8 positive only in the ELISA; and profile D: anti-M2, anti-M4, anti-M8 positive in ELISA and CFT. Patients with profile A and B were found to have a rather benign course while those patients with profile C and D showed a rather progressive course when followed over a period of 6-15 years. Considering the similarities between bacterial and mitochondrial membranes, it is suggested that the formation of AMA of different specificities in PBC, especially of the anti-M2 type, may be induced by cross-reacting antigens.