The reasons for the unusual duration of the anti-streptococcal hyperimmune response in R. patients are not yet clear. The role of a genetically caused defect in the elimination of streptococcus from the body, increased susceptibility to hospital-acquired streptococcal infection is discussed, and the problem develops in P patients after the first attack.
The predisposition to P. is not limited to the special reactivity of the immune system to streptococcal infection, and, apparently, is multifactorial in nature. Testing of various genetic hypotheses has shown that P. type of inheritance corresponds to multifactorial models. Examination of families of patients with P. revealed the presence of disease in 9.6% of their parents and 8.2% of children, which is 4 times higher than the frequency of P. in the population. The role of genetic predisposition in R. is also confirmed by a significantly higher prevalence of the disease among mono-zygote twins than di-zygote twins (37.7% and 6.6%, respectively).
Studies of genetic markers have shown that among patients with R. more often observed are persons with blood groups A and B. P patients with blood group B had higher titers of antistreptoly-zina-O, which may indicate a higher sensitivity to streptococcus of people g with this blood group.
In recent years, intensive studies have been conducted on the relationship between certain rheumatic diseases and immunogenetic factors, in particular, the Histocompatibility antigen system – HLA (see Transplantation Immunity, Histocompatibility antigens). Zabriskie (J. V. Zabriskie, 1976) noticed the decrease of HLA AZ frequency in R. children, and Joshinoya, et al. (1980) found an increased HLA B5 frequency in them. Baum (J. Baum, 1979) reports two series of studies: in one of P patients was found to have a significantly increased frequency of HLA B35, and in the presence of rheumocarditis was more frequently registered HLA B18 antigen; in the other series – no difference was found in patients of P. compared to the population.
Streptococcus affects the human body with various intracellular antigens (see) and extracellular exoenzymes. Among the first, M-protein of the cell wall (virulence factor), hyaluronic acid of the capsule and numerous antigens of the cytoplasmic membrane are of paramount importance. The second includes various products of life activity of streptococcus – exoenzymes such as streptolysin-0 and S, hyaluronidase, streptokinase, deoxyribonuclease B and others. Both those and others cause the development of an immune reaction with increased formation and prolonged circulation of various anti-streptococcal antibodies (see), disrupt the phagocytic activity of neutrophils, which contributes to long-term persistence of streptococcus.
Among the mechanisms for the development of clinical manifestations of R., such as carditis, polyarthritis, chorea, erythema rings, the immune type of inflammation, immunopathological reactions, in the development of which streptococcal antigens and antibodies are most actively involved (see Immunopathology). It is believed that cross-reacting antibodies may be of great importance in the development of tissue damage in P., i.e. such antibodies, which respond to the antigens of streptococcus, react with tissue antigens of the body. A cross-reaction between the group A streptococcus polysaccharide and the epithelial cells (epithelioreticulocytes) of the v-fiber gland was found, which, according to I.M. Lyampert et al. (1975), associated with disorders of immunosuppressor function of the thymus gland and T-lymphocytes functioning, development of cell-mediated autoimmune reaction.
Other cross-reacting antibodies, in particular, streptococcal antibodies cross-reacting with myocardial sarcomal antigens, have also been detected.
The pathogenetic value of circulating anticardial antibodies is unequivocally confirmed by the discovery of immunoglobulin deposits (see) and complement deposits (see) in myocardium tissue, which was first noticed by Kaplan (M. N. Kaplan), et al. (1964) in the study of the heart of a child who died from the effects of pancreditis. Fixed immunoglobulins are found in the myocardium of the deceased from R. or in the tissue of the atrial ears removed by a comissurotomy. Other antibodies are also detected in P patients, which may have pathogenetic value. In this regard, circulating antibodies to the components of connective tissue – fibroblasts, structural glycoprotein, proteoglycans (see Autoantibodies) – are of most interest.