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Parasite Versus Host: Pathology and Disease
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
Various mechanisms have been proposed as an explanation for why self-tolerance is lost. The release of host antigens that are normally sequestered and therefore not usually available to immune surveillance explains some autoimmunity. An example is sympathetic ophthalmia. Trauma to an eye can release antigens normally not encountered by the immune system, resulting in immune system priming and a subsequent attack on the eye. Inappropriately high expression of MHC on the surface of pancreatic islet cells may be involved in the development of insulin-dependent diabetes. In some cases, however, molecular mimicry may be to blame. In this scenario, an individual is infected with a pathogen bearing antigens that are very similar to host antigens. Lymphocytes, activated in response to the pathogen, also direct their immune assault against the similar host antigen, damaging the tissue bearing those antigens. Such molecular mimicry has been difficult to demonstrate; by the time the affected individual starts displaying symptoms of autoimmunity, the offending pathogen is usually long since destroyed. Yet for some conditions, the evidence for such molecular mimicry is strong. Rheumatic fever, for instance, is initiated by a Streptococcus infection. In some individuals, antibodies generated against the bacterium cross-react with antigens on heart valves.
The Inducible System: Antigens
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Some microorganisms may produce molecules similar to those of the host but sufficiently different to be treated as foreign. Here too the antibody products of the immune response may react with the related host molecules. Rheumatic fever is probably initiated by infection with streptococci. The autoimmune reaction against heart and joint tissue which follows is a result of similarity of molecules in the parasite and the tissue.
Myocarditis
Published in Mary N. Sheppard, Practical Cardiovascular Pathology, 2022
Although strep throat is common, rheumatic fever is rare in the US, UK and other developed countries. Acute rheumatic fever and rheumatic heart disease are diseases of lower socioeconomic groups in developing countries. The disease is now virtually extinct in developed countries, but remains endemic in many parts of the developing world, in particular those which are semi-tropical. The disease thrives in crowded deprived communities with a high proportion of infants in the population, such as Africa, India South America, the Pacific and the Middle East. The disease occurs after a latent period of 2–6 weeks. Usually the patient develops fever, a flitting arthropathy and skin rashes or nodules. Concomitant with this is cardiac involvement. Guidelines have been drawn up to unify the diagnosis of acute rheumatic fever (Table 6.6) and there should be serological or culture evidence of prior streptococcal infection plus one major and two minor criteria or two major criteria. The current focus of global efforts at prevention of rheumatic heart disease is on secondary prevention (regular administration of penicillin to prevent recurrent rheumatic fever), although primary prevention (timely treatment of streptococcal pharyngitis to prevent rheumatic fever) is also important in populations in which it is feasible.
Identifying the response process validity of clinical vignette-type multiple choice questions: An eye-tracking study
Published in Medical Teacher, 2023
Francisco Carlos Specian Junior, Thiago Martins Santos, John Sandars, Eliana Martorano Amaral, Dario Cecilio-Fernandes
Boy, three-year-old, was brought to the Emergency Room with pain in the right lower limb and difficulty in walking for one day. Family history: brother with an upper respiratory tract infection for 10 days. Physical examination: T = 36.8 °C; RR = 16 breaths per minute; HR = 90 beats per minute; Limbs: limitation of internal and external rotation of the right hip; does not perform complete extension of the right lower limb. The most likely diagnosis is:Rheumatic fever.Legg-Calve-Perthes disease.Transient synovitis.Juvenile idiopathic arthritis.
Concomitant rapidly progressive glomerulonephritis and acute rheumatic fever after streptococcus infection: a case report
Published in Paediatrics and International Child Health, 2022
Suwanna Pornrattanarungsi, Sudarat Eursiriwan, Yupaporn Amornchaicharoensuk, Chutima Chavanisakun, Ornatcha Sirimongkolchaiyakul
Acute post-streptococcal glomerulonephritis (APSGN) and acute rheumatic fever (ARF) are common, non-suppurative disorders which occur after group A streptococcal (GAS) infection, especially acute pharyngitis or skin infection [1,2]. Typical clinical manifestations in acute glomerulonephritis are hypertension, oedema and glomerular haematuria. Acute rheumatic fever may be associated with cardiac lesions together with systemic signs and symptoms such as polyarthritis, chorea, erythema marginatum, fever and increased inflammatory markers. The diagnosis of APSGN or ARF requires laboratory evidence of preceding streptococcal infection. However, the main mechanism underlying both diseases varies. Immune complex formation is the crucial pathogenesis of APSGN whilst ARF can arise as a result of molecular mimicry [3]. Rarely, however, both occur simultaneously.
Group A streptococcal M-protein specific antibodies and T-cells drive the pathology observed in the rat autoimmune valvulitis model
Published in Autoimmunity, 2019
Suchandan Sikder, Georgina Price, Md Abdul Alim, Anil Gautam, Robert Scott Simpson, Catherine Margaret Rush, Brenda Lee Govan, Natkunam Ketheesan
ARF/RHD is clinically diagnosed when a patient presents with two major manifestations or one major and at least two minor manifestations according to the modified Jones Criteria for the diagnosis of ARF/RHD 2015 [53]. Prolongation of P-R interval in ECG is one of the Jones Minor Criteria for the diagnosis of rheumatic fever. Moreover, echocardiographic screening of suspected ARF patients is the latest recommendation that has been included in the 2015 revised Jones Criteria. It is helpful in diagnosing clinical and subclinical carditis even in the absence of classical auscultatory findings [53]. Prolongation of P-R interval is a minor criterion and in a typical ECG trace indicates delay in ventricular depolarization due to myocardial pathology. In the current study, rats receiving serum or splenocytes or both serum and splenocytes showed prolonged P-R intervals in ECG. In the current study, thickening of mitral valves of rats transferred with serum and splenocytes from GAS rM5 injected rats was observed as echo-dense white leaflets in echocardiography. Echo dense foci on mitral leaflets were also observed as white and round structures on the leaflets. The results were similar to the echocardiographic findings of donor rats and in patients with ARF/RHD [10].