Murine spleen and lymph node cellular composition and function during cyclophosphamide and splenectomy induced resistance to Toxoplasma gondii

Infection with Toxoplasma gondii alters lymphotoxin expression associated with changes in splenic architecture

B cell responses are required for resistance to Toxoplasma gondii; however, the events that lead to production of class-switched antibodies during T. gondii infection have not been defined. Indeed, mice challenged with the parasite exhibited an expansion of T follicular helper cells and germinal center B cells in the spleen. Unexpectedly, this was not associated with germinal center formation and was instead accompanied by profound changes in splenic organization. This phenomenon was transient and was correlated with a decrease in expression of effector proteins that contribute to splenic organization, including lymphotoxins α and β. The importance of lymphotoxin was confirmed, as the use of a lymphotoxin β receptor agonist results in partial restoration of splenic structure. Splenectomized mice were used to test the splenic contribution to the antibody response during T. gondii infection. Analysis of splenectomized mice revealed delayed kinetics in the production of parasite-specific antibody, but the mice did eventually develop normal levels of parasite-specific antibody. Together, these studies provide a better understanding of how infection with T. gondii impacts the customized structures required for the optimal humoral responses to the parasite and the role of lymphotoxin in these events.

Heat stress-induced modulation of host defense against Toxoplasma gondii infection in mice

This study examined the effects of burn injury on murine immune response against Toxoplasma gondii infection. Male C57BL/6 mice were divided into 3 groups: T. gondii infection (group T), burn injury (group B), and burn injury followed by T. gondii infection (group BT). The survival of group BT was significantly lower than those of group B and group T. Parasite abundance in the tissues was determined by quantitative competitive-polymerase chain reaction. Group BT exhibited significantly higher numbers of T. gondii than group T. Antibody production against T.g.HSP30 in group BT was significantly lower than that in group T, whereas no significant difference was observed in SAG1-specific antibody production. Delayed-type hypersensitivity (DTH) specific for 2,4-dinitrofluorobenzene (DNFB) of both group B and group BT was significantly lower than that of group T. One week after infection, serum interferon-gamma (IFN-gamma) and interleukin (IL)-10 levels in group BT were significantly lower, whereas serum IL-6 levels were significantly higher than in group T Serum TNF-alpha levels in both group T and group BT were elevated at 1 wk after infection, although there was no significant difference between them. Serum IFN-gamma, IL-10, and TNF-alpha levels in group B were not elevated during the experimental term. In conclusion, the impaired antigen-specific antibody production and DTH response, together with the modulated patterns of cytokine responses, seemed to be strongly involved in the development of burn-induced immunosuppression and the consequent increased susceptibility to T. gondii infection in mice.

Enhanced clearance of Escherichia coli and Staphylococcus aureus in mice treated with cyclophosphamide and lactoferrin

Previous studies on cyclophosphamide (CP)-immunocompromised mice showed accelerated reconstitution of immune system function following oral treatment with lactoferrin (LF). The aim of this investigation was to evaluate the ability of mice, treated with a sublethal dose of CP and given LF, to combat bacterial infections. Mice were injected with a single, intraperitoneal dose of CP (350 mg/kg body weight). One group of CP-treated mice was also given LF in drinking water (0.5% solution) for 14 days. Untreated and LF-treated mice served as controls. On day 15 following CP administration, mice were infected intravenously with 10(8) Escherichia coli or 5 x 10(7) Staphylococcus aureus. Twenty-four hours later, the number of colony-forming units (CFU) in spleens and livers were determined. Phenotypic analysis of blood leukocytes was determined, as well as the ability of splenic and peritoneal cells to produce IL-6 spontaneously and in the presence of lipopolysaccharide (LPS). Treatment with CP, or with CP and LF, led to profound reduction of E. coli CFU in the liver and the spleen; treatment with LF alone had significant inhibitory effects on organ enumerated CFU. S. aureus CFUs were also significantly reduced in spleens of mice treated with CP or CP/LF and, to a lesser degree, after LF alone. These effects were also significantly reduced in the livers. Analysis of blood cellular phenotype revealed total number of peripheral leukocytes was lower in the CP-treated group (52.6%) but not significantly different from control values in CP/LF and LF-treated groups (90.7% and 104.6%, respectively). Conversely, percentage of blood neutrophils was markedly elevated in CP and CP/LF groups--62% and 42.5% vs. 18.4% in controls. These findings were accompanied by production of IL-6 by splenic and peritoneal cells which was significantly increased in CP- and CP/LF-treated groups. It was concluded that the increased clearance of bacteria in the organs of mice treated with CP and CP/LF may result from a rise in the number of neutrophils infiltrating the organs and contributing to accelerated clearance of bacteria. The study also suggests that the ability of cells from CP- and CP/LF-treated mice to produce significantly more IL-6 may also contribute to increased resistance to infections. Lastly, together with our previous data, this study indicates that LF used to reconstitute the antigen-specific immune response in CP-treated mice does not impair their resistance to infection.

Asplenic-hyposplenic overwhelming sepsis: postsplenectomy sepsis revisited

Absence of the spleen or splenic function predisposes individuals to risk of overwhelming infection. These infections are most often due to encapsulated organisms, especially pneumococcus, Haemophilus influenzae type b, and meningococcus, but any bacterial agent may cause the rapid onset of septicemia, meningitis, pneumonia, and shock characteristic of the asplenic-hyposplenic condition. The risk is greatest in infants and young children, but asplenic-hyposplenic adults also have an increased risk of infection. Prophylactic antibiotics and immunization with polyvalent pneumococcal, H. influenzae type b, and meningococcal vaccines have reduced the incidence of infections in asplenic-hyposplenic individuals, but even these measures have not eliminated the risk. Surgeons have adopted techniques to save as much splenic tissue as possible and some splenic functions, such as pitting red cells, have been preserved, but conservative surgery has not provided total protection against overwhelming infection. Therapies designed to interrupt the cascade of overwhelming sepsis have not yet been successful. In those cases in which the spleen is surgically removed, the underlying disease or condition leading to splenectomy influences the risk of sepsis. Splenectomy incidental to other operations, such as gastrectomy, results in the lowest risk for overwhelming infection, but this is still some 35-fold greater than the risk for overwhelming infections in the general population. In increasing order of risk, the other main indications for surgical removal of the spleen are idiopathic thrombocytopenia purpura, trauma, transplantation procedures, hereditary spherocytosis, staging Hodgkin's disease, portal hypertension with hypersplenism, and thalassemia. Pathologists should comment on the risk of overwhelming sepsis when spleens are processed as surgical specimens, and should carefully weigh all splenic tissue, including accessory spleens and splenic implants (splenosis), in autopsy cases with and without overwhelming sepsis.

Immunoregulatory potential of exogenous Schistosoma mansoni soluble egg antigen in a model of experimental schistosomiasis--I. Regulation of granuloma formation in vivo

This study was undertaken to assess the optimum conditions required to reduce the vigorous host granulomatous reaction around Schistosoma mansoni eggs. Soluble schistosomal egg antigen (SEA) at a concentration of 10 or 100 micrograms protein was administered i.p. or i.v. into unprimed C57BL/6 mice. SEA was injected either alone or in combination with cyclophosphamide (CY) 100 or 50 mg/kg via i.p. route. Seven or 14 days later viable eggs of S. mansoni were injected via the tail vein into treated groups and untreated normal controls. Mice were sacrificed 8, 16 and 24 days after the injection of eggs. The lungs were removed for histopathological study, measurement of granuloma diameter and phenotypic analysis of granuloma intralesional T-cell subsets. Compared to untreated controls, the lower concentration of SEA (10 micrograms) administered by the i.v. route 7 days before egg injection, induced a significant reduction in granuloma diameter 16 days after egg injection than that by the i.p. route or at a higher SEA concentration (100 micrograms). Compared to untreated controls, the higher dose of CY (100 mg/kg), given i.p. alone or in combination with 10 micrograms SEA by the i.v. or i.p. route, induced a significant reduction in granuloma diameter, while 50 mg/kg CY did not cause any reduction. The reduction in granuloma diameter by i.v. administration of low SEA concentration alone or in combination with CY IP, was associated with a decrease in the granuloma intralesional L3T4+/Lyt2+ ratio. The decrease in the ratio was due to an increase in Lyt2+ cells. The results suggest that the use of low dose SEA by the i.v. route alone or combined with an immunosuppressive drug ameliorates pathological changes concurrent with S. mansoni infection.

[Effects of interferon-gamma in T cell subsets of mice infected with Toxoplasma gondii]

This study was performed to evaluate differences of T cell subsets according to the injection period of recombinant mouse interferon-gamma (IFN-gamma) in acute Toxoplasma gondii infection. Each mouse was infected intraperitoneally with 100 cysts of Beverley strain T. gondii, and injected with 5 x 10(4) units of IFN-gamma every other day two tmres. The percentage of Thy-1,2 cells and L3T4/Ly-2 cell ratio were significantly increased in the mice that received two doses of IFN-gamma on days 2 and 0 before infection, or days 0 and 2 after infection. The percentage of Ly-2 cells decreased in the IFN-gamma injected groups at the 3rd and 4th week after infection. The results suggest that administration of IFN-gamma to T. gondii-infected mice improves the changed population of T cell subsets to a normal state, especially when IFN-gamma was injected just after the infection.

Effects of cyclophosphamide and dexamethasone on mast cell populations in Hymenolepis microstoma-infected mice

Antineoplastic cyclophosphamide (CY) significantly reduced the survival and the weight of Hymenolepis microstoma in mice. Corticosteroid dexamethasone (DEX), on the other hand, did not influence the worm survival and the worms in DEX-treated mice became significantly heavier. Both immunosuppressants abolished H. microstoma-induced bile duct hypertrophy and submucous enteritis and lowered the number of mast cells (MC) in these regions. CY appeared to be more effective in depleting the bile duct MC whereas DEX seemed to affect more the duodenal MC population.