T-Cell-dependent antibody response to the dominant epitope of streptococcal polysaccharide, N-acetyl-glucosamine, is cross-reactive with cardiac myosin.

Autoantibodies against myosin are associated with myocarditis and rheumatic heart disease. In this study, the antigenic cross-reactivity of myosin and N-acetyl-glucosamine (GlcNAc), the dominant epitope of Group A streptococcal polysaccharide, was examined. Six antimyosin monoclonal antibodies (MAbs) derived from mice with cardiac myosin-induced myocarditis were characterized. All MAbs cross-reacted with GlcNAc, mimicking a subset of MAbs derived from rheumatic carditis patients that bind both myosin and streptococcal polysaccharide. Variable (V) region gene usage was diverse, with five of six MAb heavy-chain V regions encoded by distinct members of the J558 family and the sixth encoded by a member of the VGAM3.8 family. Light-chain V-region segments were derived from the Vk1, Vk4/5, Vk10, and Vk21 families. These antimyosin, anti-GlcNac MAbs demonstrated several T-cell-dependent features: they were predominantly immunoglobulin G, were encoded by V-region genes expressed late in development, and displayed somatic mutation. A direct correlation between the extent of somatic mutation and the affinity for myosin was observed. Affinity for GlcNAc also increased with the frequency of mutation, demonstrating that affinity maturation can occur simultaneously for both self antigen and foreign antigen. Based on these observations, we immunized mice with GlcNAc coupled to bovine serum albumin and demonstrated that a T-cell-dependent response to GlcNAc leads to antimyosin reactivity. We speculate that the pathogenic antibody response in rheumatic carditis may reflect the conversion of a T-cell-independent response to GlcNAc to a T-cell-dependent cross-reactive response to GlcNAc and myosin.

Autoimmune myocarditis does not require B cells for antigen presentation.

T cells constitute the pathogenic effector cell population in autoimmune myocarditis in BALB/c mice. Using mice rendered deficient for B cells by a targeted disruption to the IgM transmembrane domain or by treatment with anti-IgM Ab from birth, we asked whether B cells are a critical APC in the induction of autoimmune myocarditis. B cell-deficient mice immunized with cardiac myosin develop myocarditis comparable in incidence and severity to that in wild-type mice, suggesting that autoreactive T cells that cause myocarditis in BALB/c mice are activated by macrophages or dendritic cells. Since it does not appear that presentation of cryptic epitopes is critical for the breakdown of self tolerance, potentially pathogenic T cells recognizing dominant myosin epitopes must have escaped tolerization. Either anatomic sequestration of cardiac myosin peptide-MHC complexes or subthreshold presentation of cardiac myosin peptides by conventional APC can explain the survival of these autoreactive T cells.

Genetic control of autoimmune myocarditis mediated by myosin-specific antibodies.

Autoimmune disease involves both the development of autoreactivity and the expression of organ damage, and susceptibility is genetically complex. We recently reported that in autoimmune myocarditis susceptibility to antibody-mediated cardiac injury is strain specific. DBA/2 mice develop myocarditis following administration of myosin-specific antibody, while BALB/c mice do not. This susceptibility appears to be controlled by expression of myosin in the myocardial extracellular matrix. CByD2F1 mice are both resistant to induction of myocarditis and do not demonstrate extracellular myosin, indicating a recessive genetic component to these traits. A backcross analysis of susceptibility using DBA/2xCByD2F1 mice revealed a locus on chromosome 12 that is strongly linked with myocarditis. In male mice there was a second region on chromosome 1 that also contributes to disease susceptibility. However, genetic susceptibility in both female and male mice was genetically complex. This study demonstrates that the genetic basis of tissue injury can be analyzed separately from the genetic basis of autoreactivity. Future studies will determine whether the genetic factors identified in this study are also involved in susceptibility to rheumatic fever.

Autoimmunity in heart disease: mechanisms and genetic susceptibility.

Recent studies of heart disease suggest that immunologically mediated processes often accompany cardiac injury and can contribute to pathogenesis. Murine models of myocarditis have provided insight into the mechanisms by which autoimmune responses to cardiac antigens arise and cause tissue pathology. It is now evident that T cells, cytokines and antibodies can all contribute to cardiac injury. Furthermore, murine models have demonstrated that both the propensity to develop autoreactivity following cardiac injury and the vulnerability of the heart to these responses are under genetic control. Continued studies will help to identify susceptibility genes and might aid in the development of strategies to protect individuals at risk from immunologically mediated damage following cardiac injury.

Interaction between allopurinol and copper: possible role in myocardial protection.

Allopurinol, a potent inhibitor of xanthine oxidase, is known to effectively protect the heart against damage in patients undergoing cardiac bypass surgery. There is still an ambiguity concerning the presence of xanthine oxidase in the human heart. Thus, the mechanism underlying the protective effect of allopurinol is unclear. Transition metal ions, such as iron and copper, can participate in single-electron reactions and mediate the formation of oxygen-derived free radicals. In this study the interaction between allopurinol and Cu(II) was investigated. Spectrophotometric investigation shows that allopurinol (0-0.8 mM) form a 1:1 complex with Cu(II) ions (0-0.8 mM) with a specific absorbance peak at 364 nm. Also, the rate constant (k) for the copper-catalyzed aerobic oxidation of ascorbate was markedly decreased in the presence of allopurinol (from 0.068 min-1 to 0.014 min-1). Allopurinol substantially reduced the copper-mediated and ascorbate-driven DNA breakage. Spectrophotometric measurements did not indicate a specific interaction between iron ions and allopurinol. It is suggested that the beneficial effects of allopurinol during reperfusion of the heart could stem from its chelation of copper, yielding a complex with low redox activity.

Allergy to human seminal fluid: characterization of the allergen and experience with immunotherapy.

A 20-year-old woman was observed with a history of a severe generalized systemic reaction after topical contact with seminal fluid. A prick test with undiluted seminal fluid produced a 5.0 mm wheal-and-flare response with pseudopods. Prick tests with saliva and serum from the same source as the seminal fluid were negative. Measurement of IgE antibody to seminal-fluid allergen with a Biotin-Avidin ELISA technique yielded strong activity. No IgG antibody could be detected. Significant prick test reactivity could be found in Sephadex G-100 fractions that had a molecular weight range of 12,000 to 75,000 daltons and that contained approximately 5% of the total protein in the starting material. Isoelectric focusing fractions with strong skin test reactivity had a pI range of 5.4 to 6.6. These fractions contained one major protein band. Immunotherapy was conducted with a Sephadex fraction of seminal fluid during a 24-month period. A cumulative dose of 32 mg of protein was administered. No side effects other than local swelling occurred. Ten months after the start of immunotherapy, IgE antibody became unmeasureable, an effect that was demonstrated not due to the inhibitory effect of IgG antibody. IgG antibody rose progressively in this period. Clinically, the patient became less sensitive to topical contact. Although the natural history of seminal-fluid allergy is not known, immunotherapy may be effective.

Sarcomas induced by injection of simian virus 40 into neonatal CFW mice.

Sarcomas were induced in CFW mice by the iv inoculation of simian virus 40 (SV40) in neonatal animals. Infection with murine malaria parasites, Plasmodium berghei yoelli, decreased the latency and increased the incidence and invasiveness of the tumors. All mice given both SV40 and P. berghei yoelli had sarcomas of the liver and spleen at 9 months of age. At 11 months of age, 70% of the SV40-inoculated mice had sarcomas of the liver indistinguishable from those in the group given both pathogens. Only 1 lung metastasis was seen in the SV40-treated group. The sarcomas contained SV40 T-antigen as revealed by the indirect immunofluorescence technique. Among adult CFW mice given iv injections of SV40, only 2 tumors were found at 11 or 12 months after virus inoculation. Both tumors were in the lungs; 1 was an adenoma and 1 was a papillary adenocarcinoma. Neither gave a positive reaction with the immunofluorescence test.

Immunoregulatory function of specific IgG. II. Clinical evaluation of combined active and passive immunotherapy.

Based upon previous clinical data suggesting that the potential therapeutic benefits of hyperimmune specific IgG could involve neutralization and regulatory effects, this cooperative study evaluated the efficacy and safety of combined active and passive immunotherapy in previously untreated ragweed-sensitive patients. Symptom scores and indices of patients receiving ragweed-specific globulin plus rush desensitization with ragweed extract were significantly reduced (p less than 0.05), as compared to control patients treated with albumin and active rush immunotherapy. Postseasonal RAST levels were either unchanged or decreased in 28 of 33 patients receiving hyperimmune gamma-globulin. These data were significantly different from those in albumin-treated patients (p less than 0.002). The usual anamnestic rise of ragweed-specific IgE was modified without affecting the ongoing synthesis of ragweed specific IgG. Mild constitutional symptoms were observed in patients undergoing rush immunization, but the overall procedure was relatively well tolerated and no serious or treatment-refractory constitutional problems were encountered. This clinical trial suggests that ragweed immune gamma-globulin might be a useful therapeutic adjunct when administered in close association with optimal amounts of allergen.