Thymocytotoxic autoantibodies found in mice infected with Schistosoma japonicum

Infection-Associated Thymic Atrophy

The thymus is a vital organ of the immune system that plays an essential role in thymocyte development and maturation. Thymic atrophy occurs with age (physiological thymic atrophy) or as a result of viral, bacterial, parasitic or fungal infection (pathological thymic atrophy). Thymic atrophy directly results in loss of thymocytes and/or destruction of the thymic architecture, and indirectly leads to a decrease in naïve T cells and limited T cell receptor diversity. Thus, it is important to recognize the causes and mechanisms that induce thymic atrophy. In this review, we highlight current progress in infection-associated pathogenic thymic atrophy and discuss its possible mechanisms. In addition, we discuss whether extracellular vesicles/exosomes could be potential carriers of pathogenic substances to the thymus, and potential drugs for the treatment of thymic atrophy. Having acknowledged that most current research is limited to serological aspects, we look forward to the possibility of extending future work regarding the impact of neural modulation on thymic atrophy.

Antinuclear antibodies and interleukin responses in patients with Schistosoma japonicum infection

Schistosomiasis poses a serious threat to public health, and the infection will develop into chronic and advanced late-stage disease if not treated. Apart from the clinical signs due to immune reactions to schistosome eggs trapped in host tissues, it also increases the risk for the development of autoimmunity reflected by dysfunctional, auto-reactive antibodies. Antinuclear antibodies (ANA) have been reported in schistosomiasis due to S. mansoni and S. haematobium. We demonstrate ANA in schistosomiasis japonica and explore the relationship between this infection and autoimmune disease by measuring ANA and interleukin (IL)-10, IL-12 and IL-17 responses in the sera of 125 Chinese patients with different stages of schistosomiasis japonica. The incidence rates of ANA in the patients with acute, chronic and late stages of schistosomiasis infection were 6.7%, 23.3% and 70.0%, respectively, with statistically significant differences between each stage (P = 0.000). IL-17 concentrations were high at the acute stage of schistosomiasis compared to the other stages of the disease (P = 0.000). This pattern was also seen for IL-10 and IL-12 concentrations (P = 0.01). IL concentrations in patients in the chronic and late stages of the disease were low and showed no difference compared to the healthy adults.

Schistosoma japonicum soluble egg antigens activate naive B cells to produce antibodies: definition of parasite mechanisms of immune deviation

This study analysed the effect of Schistosoma japonicum egg antigens (SEA) on the activation of lymphocytes from naive mice. T cells were found to be unaffected by SEA. B cells, however, were activated by SEA without participation of adherent cells such as macrophages. B-cell activating factor(s) in SEA were distributed into a fraction of M(r) 120,000 and a fraction of M(r) 650,000 by gel filtration. However, a fraction of M(r) 120,000 demonstrated the presence of a limited number of components by polyacrylamide gel electrophoresis (PAGE) under non-denaturing conditions. These activating factor(s) were destroyed by peroxidase oxidation, heat treatment, chymotrypsin and trypsin digestion. These results indicate that the B-cell activating factor(s) in SEA contain both carbohydrate and protein. IgM antibodies were detected in the culture supernatant of SEA-activated B cells after 48 hr in culture, but IgG antibodies were undetected in culture. These antibodies did not react with SEA but reacted with sheep, horse, mouse red blood cells, carbonic anhydrase and autoantigens in myelinated nerve fibres of cerebrum as well as luminal surface and parietal cells of the stomach of naive mice. Thus our data demonstrated that SEA directly stimulates naive B cells to produce antibodies against heterophile and autologous antigens.

Deficiency of interleukin-2 production upon addition of soluble egg antigen to cultures of isolated hepatic granulomas or hepatic granuloma cells from mice infected with Schistosoma japonicum

Schistosoma japonicum-infected C57BL/6 mice show similar dynamics of hepatic granulomatous inflammation and delayed hypersensitivity elicited by soluble egg antigens (SEA) which reach peak levels at 9 weeks of infection and then spontaneously regress. In an attempt to link the level of interleukin 2 (IL-2) production to the spontaneous regression of hepatic granulomatous inflammation, the study determined the dynamics of IL-2 production by SEA-challenged isolated hepatic granulomas (HG) and cells isolated enzymatically from the HG. The production of IL-2 by SEA-stimulated HG or HG cells reached its peak when these preparations from 9-week-infected mice were stimulated and fell thereafter. Some possible mechanisms that might explain the IL-2 deficiency were examined. This deficiency is not due to the in vitro binding of IL-2 by the HG cells of infected mice and is, therefore, due rather to underproduction of IL-2. The deficiency was also not explained by reduced numbers of antigen-presenting cells (macrophages or B cells) or of L3T4+ T lymphocytes. In vitro SEA-induced IL-2 production by HG cells from acutely infected mice was suppressed consistently by Lyt-2+ T cells from the spleens and in the majority of our experiments by Lyt-2+ T cells from the HG of mice infected for 10 weeks. These findings are consistent with the main features of our working hypothesis, but it remains to be proven that in vivo deficiency of lymphokine(s) such as IL-2 is responsible for the spontaneous decrease in granulomatous inflammation and that this lymphokine deficiency is a result of suppression.

Deficiency of interleukin-2 activity upon addition of soluble egg antigen to cultures of spleen cells from mice infected with Schistosoma japonicum

Schistosoma japonicum-infected C57BL/6 mice show similar dynamics of hepatic granulomatous inflammation (HGI) and delayed hypersensitivity (DH) elicited by soluble egg antigens (SEA) which reach peak levels at 9 weeks of infection and then spontaneously regress. The in vitro SEA-induced proliferation of spleen cells (SC) from infected animals attained its high point and then declined when SC from 5-week-infected mice were used. The present study determined the dynamics of interleukin-2 (IL-2) production by SEA-challenged SC from infected mice in an attempt to link the level of IL-2 production to the spontaneous regression of the aforementioned T-cell-mediated immune responses. The production of IL-2 by SEA-stimulated SC reached its peak when cells from 7-week-infected mice were challenged at least 2 weeks after the peak of the proliferative response, but declined at about the same time as the HGI and DH responses. Therefore, the decline in IL-2 activity cannot alone explain the diminished proliferative response but could account for the reduction in HGI and DH in vivo. Some possible mechanisms that might explain the IL-2 deficiency were examined. This deficiency is not due to the in vitro binding of IL-2 by the SC of infected mice and is, therefore, likely to be due to underproduction of IL-2. Nor is the deficiency explained by reduced numbers of antigen-presenting cells (macrophages and B cells) or of L3T4+ T lymphocytes or by suppression of IL-2 production by macrophages or macrophage products such as prostaglandins. However, suppression of IL-2 production was observed consistently upon coculture of SC from acutely infected mice with SC from mice infected for 10 weeks. The cells which suppress appear to be Lyt2+ T cells. The data are consistent with the hypothesis that suppressor T cells inhibit the production of IL-2 and perhaps of other cytokines or lymphokines and that this suppression explains the spontaneous down-regulation of HGI which occurs during schistosomiasis japonica.

Studies on the immunological disturbance in murine schistosomiasis japonica from the viewpoint of the interleukin cascade reaction

We examined the mechanisms of disturbed T-lymphocyte function that occurred during Schistosoma japonicum infection of BALB/c mice from the viewpoint of the interleukin cascade reaction. Each point of the interleukin cascade reaction was examined. First, IL-1 production by adherent peritoneal or spleen cells, as a source of macrophages, was normal or rather enhanced during the infection, the values being 100-180% of the control. Secondly, proliferative response to exogenous IL-1 of thymocytes from S. japonicum-infected mice progressively decreased during 3-7 weeks of infection. Thirdly, IL-2 production of S. japonicum-infected mice was significantly inhibited, even at 2 weeks of infection, and the activity was 10-20% of the control at 5-8 weeks of infection. Diminished IL-2 production was not caused by suppressive factors, such as PGE2 or suppressor macrophages, or a decrease in the number of IL-2 producing T cells. Finally, the response to exogenous IL-2 in S. japonicum-infected mice was suppressed markedly by 4 weeks of infection, and the responsiveness was reduced to 20% of the control at 8 weeks of infection. The mechanisms of disturbances in T-cell functions in S. japonicum-infected mice are discussed.

The presence of anti-sheep red blood cell heterophile antibodies and their characteristics in murine schistosomiasis japonica

Sensitive methods of an enzyme-linked immunosorbent assay (ELISA) using red blood cells (RBC) have been developed and were applied to the detection of anti-sheep red blood cell (SRBC) heterophile antibodies (Ab) present in sera of Schistosoma japonicum (SJ)-infected mice. The indirect hemagglutination test (IHA) was used for the purpose as well. By these methods a significant increase in the heterophile Ab levels was demonstrated in the mice particularly after 6-10 weeks of infection. The heterophile Ab in SJ-infected mice were predominantly immunoglobulins resistant to 2-mercaptoethanol treatment and had temperature-independent reactivity. In an attempt to investigate the immunological specificity of the heterophile Ab, various absorption tests were performed; Davidsohn's differential absorption test revealed that the heterophile Ab were distinct from Forssman antibody, Paul-Bunnell antibody and heterophile agglutinins known to appear in serum sickness. The heterophile Ab were absorbed only with SRBC and goat red blood cells, not with other species of RBC such as human O Rh-, O Rh+, A Rh+, B Rh+, mouse, ox, chicken, horse, rabbit, guinea pig, and rat RBC, or syngeneic tissue homogenates including brain, lung, liver, spleen, kidney, muscle, and thymus. This heterophile antibody response is not a consequence of a specific immune response directed to the antigens of SJ parasites, since absorption of the heterophile Ab with SJ adult worms or an egg preparation did not reduce the heterophile Ab level.

Induction of autoantibodies and circulating immune complexes in mice after injection of Brucella fraction "PI" or inoculation with live Brucella suis

"PI", a vaccinating fraction with B mitogenic and polyclonal activator (PCA) activity extracted from Brucella melitensis, was i. p. injected into B6 and DB mice. In B6 mice, this led to an important but transient increase in the level of anti-ssDNA antibodies, the induction of rheumatoid factor (RF) and the appearance of circulating immune complexes (CIC). In DB mice, on the other hand, the only significant effect consisted of a slight and ephemeral peak of CIC in sera from day 7. Similarly, while i. v. inoculation of live B. suis did not influence the levels of anti-ssDNA, RF or CIC in DB mice, in the B6 mice it exerted effects which were comparable to those of PI but considerably weaker, more transient and somewhat delayed. These results are discussed in terms of the importance and significance of strain-dependence for the induction of autoimmune phenomena by PCA and microbial infections.

Atrophy of the thymic cortex in mice with granulomatous schistosomiasis mansoni

Thymic histopathology and granulomatous hypersensitivity were examined in CBA/J mice infected with varying numbers of Schistosoma mansoni worms. At the acute phase (8 weeks) of infection, the thymi of infected mice showed depletion of cortical lymphocytes that resulted in loss of distinction in the corticomedullary region. The degree of cortical depletion correlated directly with the intensity of infection, as assessed by total egg burden of the liver. Adrenalectomy of heavily infected mice 5 to 6 weeks after infection did not alter the course of cortical lymphocyte depletion. Thymus mass was diminished by as much as 80% in heavily infected mice. However, the thymi of lightly infected mice which survived 20 weeks of infection did not differ in histology or total tissue mass from age-matched uninfected controls. Adult thymectomy at 3 weeks of infection did not abrogate the spontaneous modulation (diminution) of granuloma formation in 20-week infected mice, although spleen cells from these mice failed to adoptively transfer suppression. Heavily infected mice which did not survive beyond the acute phase (8 to 9 weeks) of infection displayed a diminished granulomatous response that was partially restored by thymectomy carried out at 5 to 6 weeks of infection. Spleen cells from heavily infected mice (8 weeks) adoptively suppressed the granulomatous response in lightly infected recipients. It is concluded that histological changes observed in the thymus concurrent with egg dissemination and granulomatous hypersensitivity correlated with T cell-mediated regulatory events.