Search PubMed⌕ Search

Biomedical subjects

T C Jones

Publications and source records attributed to T C Jones.

At least 55 records · Page 3Linked to original sources
PubMed1987

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

Murine toxoplasmosis caused by a low virulence, cyst-forming strain of Toxcoplasma gondii (Pe strain) is characterized by splenomegaly, lymphadenopathy, decreased delayed-type hypersensitivity (DTH), and the presence of toxoplasma cysts in brain tissue. Cyclophosphamide (CY) in a single dose of 100 mg/kg injected 3 days before infection, or splenectomy 3 weeks before infection, augmented DTH and decreased the number of toxoplasma brain cysts. CY-induced augmentation of resistance during the first 3 weeks of murine toxoplasmosis was associated with: (1) an increase in mononuclear phagocytes and a decrease in T lymphocytes (including Lyt2+ cells) in spleens and lymph nodes; (2) suppressed toxoplasma antigen induced proliferation of cultured spleen cells: (3) augmentation of antigen induced proliferation of cultured lymph node cells; and (4) low levels of interferon-gamma production in both spleen and lymph node cultures. The best correlate of the enhanced in-vivo effects of CY was proliferation of nylon wool-purified lymph node cells to toxoplasma antigen. The presence of Lyt2+ cells in lymph nodes of toxoplasma infected mice inhibited maximal proliferation.

Animals↗
PubMed1987

The effect of intracellular Chlamydia psittaci on lysosomal enzyme activities in mouse peritoneal macrophages.

Live or heat killed (30 min at 56 degrees C) Chlamydia psittaci elementary bodies (EB) were phagocytosed by mouse peritoneal macrophages. Inoculation with killed Chlamydia caused rises in three lysosomal enzyme activities tested, especially in acid phosphatase activity. In contrast, after infection with live Chlamydia, only a negligible increase was seen in acid phosphatase activity, and no change in the activities of beta-glucuronidase and cathepsin D was observed. It was concluded that regulation of lysosomal enzyme synthesis in macrophages may be linked to signals mediated by phago-lysosome fusions.

Acid Phosphatase↗
PubMed1986

Leishmania donovani: an opportunistic microbe associated with progressive disease in three immunocompromised patients.

Three cases are described showing that Leishmania donovani can cause progressive disease in immunocompromised hosts. The first patient was receiving corticosteroid therapy for ulcerative colitis and the second corticosteroids and cyclophosphamide for proliferative glomerulonephritis; in the third patient, leishmaniasis occurred after a long episode of hepatosplenic schistosomiasis and salmonella bacteraemia which was treated with chloramphenicol. In two cases, the patients had moved away from areas of L donovani transmission many years before the progressive disease occurred, consistent with long-term survival of the organism in normal hosts. L donovani should be added to the growing list of opportunistic microbial infections.

Adult↗
PubMed1986

Association of symptomatic human infection with Toxoplasma gondii with imbalance of monocytes and antigen-specific T cell subsets.

During recent symptomatic toxoplasmosis, alterations in quantity and function of mononuclear cells in peripheral blood were observed. Flow cytofluorometric analysis and differential leukocyte counts revealed increased absolute numbers of T8+ cells, Leu 7+ (natural killer/killer) cells, and monocytes. T4+ cells and HLA-DR+ cells were not significantly changed. T4/T8 cell ratios were reversed in symptomatic toxoplasmosis (0.7 +/- 0.3) and normal in chronic infection (1.7 +/- 0.5). Toxoplasma antigen induced higher numbers of T8+ and TQ1+ cells in four T cell lines from two individuals with symptomatic infection than in five T cell lines from three individuals with asymptomatic infection. Eight cloned T cell lines produced gamma interferon in an antigen-specific fashion and in higher amounts when they originated from an asymptomatic subject than from a symptomatic subject. These results indicate that marked alterations in properties of immunoregulatory cells are characteristic of recent symptomatic toxoplasmosis. The transient immune dysfunction may be a major part of the observed disease and/or a feature of successful parasitism.

Acute Disease↗
PubMed1986

A prospective study of visceral leishmaniasis in an endemic area of Brazil.

The epidemiology, clinical patterns, and risk factors for visceral leishmaniasis were prospectively studied in an endemic area of Brazil. The prevalence of disease was 3.1% for children less than 15 years of age, and the annual incidence was 4.3 cases per 1,000 children. The number of children with disease fluctuated yearly and seasonally, and distribution of the disease varied within the endemic area. Risk factors included young age (median, three years) and malnutrition before the onset of disease. Intestinal parasitism, recent migration into the area, and house location within the area did not influence the progression of infection to disease. Serological testing indicated that 7.5% of children were infected with Leishmania each year and that the ratio of disease to infection was 1:18.5 for the whole area and 1:6.5 for the section with the highest prevalence of disease. Early diagnosis and therapy altered clinical patterns of the disease.

Adolescent↗
PubMed1986

New perspectives on a subclinical form of visceral leishmaniasis.

During an epidemiological study of visceral leishmaniasis in an endemic region of Brazil, new perspectives emerged on a subclinical form of the disease. A group of 86 children with antibody to Leishmania were identified. None of these children had a history of leishmaniasis. The children were segregated into four groups: One group remained asymptomatic (n = 20), whereas another developed classic kala-azar within weeks of the index serology (n = 15). The remaining 51 patients initially had subclinical disease; 13 (25%) of these patients progressed to classic kala-azar (mean, five months). The others (75%) resolved their illness after a prolonged period (mean, 35 months). The initial illness in the subclinical group was characterized by hepatomegaly, frequent splenomegaly, intermittent cough, diarrhea, and low-grade fever. Malaise and poor weight gain were common. Giemsa-stained smears and cultures of bone marrow aspirates were usually negative for Leishmania in the absence of symptoms of classic kala-azar.

Antibodies↗
PubMed1986

Spleen and lymph node cell populations, in vitro cell proliferation and interferon-gamma production during the primary immune response to Toxoplasma gondii.

An animal model for the study of transient lymphadenopathy-splenomegaly during toxoplasmosis is presented. Injection of CBA/J mice with the low virulent, cyst-forming strain of Toxoplasma gondii (Pe strain) induces a three to four fold increase in weight and cellularity of spleen and lymph nodes with peak changes at 30-50 days after infection. The spleen displays marked haemopoiesis, a 30 fold increase in mononuclear phagocytes, and a two fold increase in Lyt2+ lymphocytes. Lymph nodes show a five fold increase in mononuclear phagocytes and a four and a half fold increase in Lyt2+ T cells. The increase in mononuclear phagocytes significantly alters T cell/macrophage ratios and this is associated with decreases in in vitro cell proliferation to mitogen and toxoplasma antigen. The relationship between alterations in cell balance of mononuclear phagocytes and T cell subsets and the expression of transient immune dysfunction can now be examined by modulating changes in these cell types.

Animals↗
PubMed1986

In vitro cultivation of Toxoplasma gondii cysts in astrocytes in the presence of gamma interferon.

Long-term culturing of Toxoplasma gondii cysts was accomplished in vitro in association with murine astrocytes and intermittent additions of gamma interferon to the media. Phase-contrast microscopy was used to follow the stages of cyst development, and electron microscopy confirmed the presence of morphologic characteristics of T. gondii cysts. T. gondii cysts formed in vitro had a single trilaminar membrane during both intracellular and extracellular existence and contained amorphous electron-dense material either throughout the cyst or in a uniform layer under the trilaminar membrane. The bradyzoites were similar to previous descriptions of tachyzoites in vitro except that they were smaller and contained numerous electron-lucent vacuoles. Gamma interferon is not necessary for cyst formation, but it controls the division of tachyzoites and may allow cysts to remain for prolonged periods without rupturing. In vitro-cultivated T. gondii cysts will be useful for producing bradyzoite and cyst antigens and for measuring the effects of antimicrobial agents and immune modulators on the viability of intracystic T. gondii.

Animals↗
PubMed1986

Evaluation of the micro enzyme-linked immunosorbent assay (ELISA) for antibodies in American visceral leishmaniasis: antigen selection for detection of infection-specific responses.

This study was designed to evaluate the ELISA for diagnosis of American visceral leishmaniasis (AVL) using antigen prepared from different Leishmania isolates and from a strain of Trypanosoma cruzi. Two Leishmania donovani chagasi isolates from Bahia and Maranhão (both states of northern Brazil), one L. donovani from Sudan, one L. mexicana amazonensis isolate, and one T. cruzi isolate were used. A total of 375 sera were tested, including 119 from AVL patients, 96 from nonleishmaniasis hospitalized patients, 20 from healthy persons, 30 from patients with mucocutaneous leishmaniasis, 28 from patients with Chagas' disease, 20 from patients with tuberculosis, 21 from leprosy patients, 27 from schistosomiasis patients and 14 from patients with systemic mycoses. The antigens prepared from L. d. chagasi (Bahia) and L. m. amazonensis showed the highest sensitivity (98% and 99%, respectively) for detecting antibodies in sera from AVL patients. However, the specificity of L. d. chagasi (Bahia) antigen was better than that of L. m. amazonensis (96% vs. 86%). Comparison among the three L. donovani isolates demonstrated that the antigen prepared with the isolate from the same area where the sera originated yielded higher mean absorbance than the others. By using spectrophotometric absorbance values it was possible to use a single dilution of serum (between 1/100-1/400) since a clear separation was seen between AVL patients and controls. No patients with the other diseases who were tested gave positive results. We suggest that ELISA can be a very convenient, sensitive, and specific test for diagnosis of AVL when soluble antigen, preferably from an isolate from the test area, is used.

Antibodies↗
PubMed1986

Selection of a skin test antigen for American visceral leishmaniasis.

Studies were designed to examine skin test responses to leishmanial antigens in American visceral leishmaniasis (AVL) in Brazil. We found that after recovery from AVL, patients had positive delayed hypersensitivity reactions to Leishmania. Different amounts of a soluble extract obtained from Leishmania donovani chagasi promastigotes were compared with whole L. d. chagasi promastigotes in persons with past AVL. The most effective soluble preparations tested contained 25 and 50 micrograms leishmanial protein. These produced positive responses in 95%-100% of the individuals with past AVL. The 25 micrograms protein dose was used in further studies. This preparation produced no positive responses in either normal controls, tuberculosis patients, or schistosomiasis patients, and less than 5% positive responses in persons with Chagas' disease. The same amount of soluble extract prepared from L. mexicana amazonensis produced 82% positive skin test responses in persons with past AVL. When persons living in an area endemic for AVL were skin tested with the 25 micrograms preparation of L. d. chagasi extract, 34.1% yielded positive tests with a low number of positive responses in young children and 48% positive in adults. Only 3.1% of the population studied had a history of AVL. We have found that positive delayed hypersensitivity response to a soluble Leishmania extract is a sensitive and specific indicator of previous infection with AVL.

Adolescent↗
PubMed1985

Immune responses to T-dependent and T-independent antigens during visceral leishmaniasis in mice: evidence for altered T-cell regulation of immune responses to non-parasite antigens.

Antibody responses to T-dependent and T-"independent" antigens were studied in disease-susceptible (BALB/c and C57BL/10) and disease-resistant (A/J) mice infected with Leishmania donovani chagasi. Disease-susceptible mice but not disease-resistant mice showed a transient decrease in PFC responses to TNP on a T-dependent carrier (BGG) during the period of 4-8 weeks after infection. Infected disease-susceptible animals also showed increased responses to TNP on a type II T-independent carrier (Ficoll), which persisted until at least 14 weeks after infection. The increased responses were associated with a significant increase in anti-TNP antibody of the IgG2b subclass. When T-enriched spleen cells from infected mice and B-enriched spleen cells from uninfected mice were transferred to irradiated recipients immunized with TNP-Ficoll, increased anti-TNP PFC were observed over numbers seen in irradiated recipients which received both B and T cells from uninfected mice. Increased responses to TNP-Ficoll were also induced by prior administration of soluble leishmania extract in CFA. Infected mice immunized with TNP-LPS, a T-independent type I antigen, also had increased anti-TNP antibody responses, but had normal anti-LPS antibody responses. The elevated antibody production which occurred in response to the T-"independent" antigens could not be attributed to the relatively low polyclonal response which occurred in both disease-resistant and disease-susceptible mice infected with L. donovani chagasi. The observations are consistent with leishmania induced, transient alterations in some T-cell functions including response to haptens on T-dependent carriers, and a lack of down regulation of T-"independent" responses. Subtle lesions in immunoregulation may be important correlates of successful protozoal infection and may be responsible for some of the immunologic manifestations of the disease.

Animals↗
PubMed1985

Absence of gamma interferon and interleukin 2 production during active visceral leishmaniasis.

The lymphocytes from eight patients with active visceral leishmaniasis (VL), a disease associated with marked immunologic dysfunction, were examined for ability to produce interleukin 2 (IL-2) and gamma interferon during in vitro cultivation. It was found that both IL-2 and gamma interferon production, in response to leishmania antigen, was absent during the active disease, but was restored after successful chemotherapy. Untreated VL patients produced IL-2 and gamma interferon when stimulated with phytohemagglutinin (PHA). Six patients with either active cutaneous or mucosal leishmaniasis, a disease not associated with immunosuppression, showed high levels of gamma interferon in response to leishmania antigen and PHA. Since IL-2 and gamma interferon have been shown to have important roles in the immune response and in the killing of leishmania, their absence may represent a key defect in the immune response in VL.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1983

A comparative study of different Leishmania tropica isolates from Iran: correlation between infectivity and cytochemical properties.

Five isolates of Leishmania tropica from southwest Iran were studied to identify correlates among human disease, animal infectivity, and surface biochemistry. Clinical patterns of the disease in humans differed. One striking strain, LT-249, produced a small dry lesion which did not heal during four years of observation. Infectivity of these L. tropica for mice was correlated with lectin agglutination patterns and interaction with macrophages. There was also a significant difference among the five isolates regarding infectivity for BALB/c mice; isolate LT-249 was not infective whereas all the others were. All isolates agglutinated with Concanavalin A (Con A), Ricinus communis and soybean agglutinin but not with four other lectins listed. However, Leishmania isolate LT-249 showed much poorer agglutination with all lectins than did the other four isolates. Two isolates were selected for detailed study of attachment to macrophages, one, LT-249, which was not infective and one, LT-252, which was infective for BALB/c mice. The number of promastigotes which attached to macrophages in vitro was the same, but the mechanism of attachment differed since only the LT-252 bound predominantly by Con A-mannose receptor interaction. These results indicate a correlation among animal infectivity, lectin agglutination, and promastigote-macrophage attachment. In particular one isolate of L. tropica which caused prolonged infection in humans was not infective in BALB/c mice, showed poor agglutination with lectins, and bound to macrophages by a different mechanism than did other isolates from the same region.

Agglutination↗
PubMed1982

Effect of hydrocortisone on macrophage response to lymphokine.

To define the suppressive effects of corticosteroids on mononuclear phagocyte antiprotozoal activity, normal resident peritoneal macrophages were exposed to hydrocortisone (HC) before, during, and after in vitro activation with cell-free supernatants (lymphokines). The presence of pharmacological concentrations of HC before or during lymphokine activation prevented normal macrophages from acquiring the capacity to either respond oxidatively to Toxoplasma gondii ingestion or to inhibit intracellular toxoplasma replication. HC had no effect, however, on the cells fully stimulated by lymphokine or on macrophages previously activated in vivo. These findings indicate that although HC does not impair the ability of activated macrophages to control intracellular protozoan infection, it does compromise the antimicrobial activity of the cell-mediated immune system by rendering normal macrophages unresponsive to lymphokine.

Animals↗