Leptin does not enhance cell-mediated immune responses following mycobacterial antigen stimulation.

BACKGROUND: Tuberculosis (TB) is a infectious disease characterised by a profound immune-endocrine metabolic imbalance, including a diminution in leptin plasma levels. Leptin appears to be the link between nutritional status and the development of a protective immune response. OBJECTIVE: To examine the effects of leptin on the proliferation and production of interferon-gamma (IFN-γ) by peripheral blood mononuclear cells (PBMC) in TB patients and healthy controls stimulated with mycobacterial antigens with or without leptin. As macrophages are key cells in mycobacterial containment, the effect of leptin on the production of interleukin (IL) 1ß and IL-1Ra by the monocytic cell line THP-1 was also studied. RESULTS: Leptin diminished the proliferative capacity of PBMC on mycobacterial stimulation, and had no effect on IFN-γ production in terms of measurements in culture supernatants or intracytoplasmic analysis using flow cytometry. Real-time polymerase chain reaction studies of PBMC from TB patients revealed a preserved expression of leptin receptor. Furthermore, IL-1ß and IL-1Ra secretion by THP-1 cells was not modified by leptin treatment. CONCLUSION: The study results do not support the utility of treatment with leptin to correct immune imbalances due to TB.

Protected Trypanosoma cruzi infection in rats born to mothers receiving interferon-gamma during gestation is associated with a decreased intramacrophage parasite growth and preferential synthesis of specific IgG2b antibodies.

We demonstrated that administration of interferon gamma (IFN-gamma) to pregnant rats conferred partial resistance in their offspring to further challenge with Trypanosoma cruzi. Because of the effects of IFN-gamma on macrophage activation and immunoglobulin isotype selection, offspring were now studied to ascertain whether this intervention modifies the in vitro replication of T. cruzi and nitric oxide (NO) production by peritoneal macrophages (PE), together with the anti-T. cruzi IgG isotypes. To evaluate the possibility of a detrimental effect of IFN-gamma, serum levels of anti-sulphatide autoantibodies were also investigated. Offspring were born to mothers undergoing one of the following procedures during gestation: treatment with recombinant rat IFN-gamma, 50,000 IU/rat, five times/week for 3 weeks, which was started on the day of mating; infection with 10(6) trypomastigotes of T. cruzi at 7, 14, and 21 days after mating plus IFN-gamma treatment as given to the former group; the same protocol except that physiological saline was injected instead of IFN-gamma; injection of physiological saline only. Offspring were challenged at weaning with a similar dose of T. cruzi, to constitute four groups of infected young, plus an additional group of age-matched uninfected rats born to control mothers. PE were harvested at day 7 postinfection (pi), exposed to parasites and further investigated for the replication of T. cruzi and NO production, whereas ELISA studies for measuring serum anti-T. cruzi IgG subclasses and anti-sulphatide autoantibodies were performed at day 30 pi. The number of intracellular parasites in PE was markedly decreased in young born to IFN-gamma-treated mothers, this not being accompanied by higher nitrite levels in culture supernatants. Offspring delivered by IFN-gamma-treated mothers showed no higher serum concentrations of anti-sulphatide autoantibodies, but exhibited a preferential synthesis of anti-T. cruzi IgG2b antibodies. This rat isotype is known to fix complement and constitutes the rat counterpart of IgG2a mouse immunoglobulins whose synthesis is favoured by IFN-gamma.

Administration of interferon-g to pregnant rats reverses the depressed adjuvant-induced arthritis of their chronically Trypanosoma cruzi-infected offspring.

We demonstrated that administration of interferon gamma (IFN-gamma) to the inbred "I" strain of pregnant rats conferred partial resistance on their offspring to challenge with Trypanosoma cruzi. We now examine if this intervention also modifies the reportedly immunodepressed cellular responses which occur during chronic infection. Offspring were born to mothers undergoing one of the following procedures during gestation: subcutaneous injections of recombinant rat IFN-gamma, 50,000 IU/rat, five times/week for 3 weeks, which was started on the day of mating (IFN-Mo); infection with 10(6) trypomastigotes of T. cruzi at 7, 14, and 21 days after mating plus IFN-gamma treatment as given to the former group (TcIFN-Mo); the same protocol except that physiological saline was injected instead of IFN-gamma (Te-Mo); injection of physiological saline only (control-Mo). All offspring groups (N = 8-10/group) were infected at weaning and were assessed 90 days later for their adjuvant-induced arthritic response or levels of major T cell subsets in spleen and lymph nodes. TcIFN-Mo and IFN-Mo offspring showed a reestablished arthritic response, which remained within the range seen in controls. Immunolabeling studies on parallel groups of 90-day-infected offspring showed that the inverse CD4/CD8 cell ratio that is usually seen in lymphoid organs from these chronically infected rats (median 0.61) appeared to have recovered in the TcIFN-Mo and IFN-Mo groups (median 1.66 and 1.78, respectively) and was not different from uninfected controls (1.96). These studies indicate that early stimulation with IFN-gamma is able to reverse the immunosuppressive state that is usually present during the chronic period of the experimental infection.

Administration of interferon-gama to pregnant rats reverses the depressed adjuvant-induced arthritis of their chronically Trypanosoma cruzi-infected offspring

We demonstrated that administration of interferon gamma (IFN-gama) to the inbred "l" strain of pregnant rats conferred partial resistance on their offspring to challenge with Trypanosoma cruzi. We now examine if this intervention also modifies the reportedly immunodepressed cellular responses which occur during chronic infection. Offspring were born to mothers undergoing one of the following procedures during gestation: subcutaneous injections of recombinant rat IFN-gama, 50,000 IU/rat, five times/week for 3 weeks, which was started on the day of mating (IFN-Mo); infection with 106 trypomastigotes of T. cruzi at 7, 14, and 21 days after mating plus IFN-gama treatment as given to the former group (TcIFN-Mo); the same protocol except that physiological saline was injected instead of IFN-gama (Tc-Mo); injection of physiological saline only (control-Mo). All offspring groups (N = 8-10/group) were infected at weaning and were assessed 90 days later for their adjuvant-induced arthritic response or levels of major T cell subsets in spleen and lymph nodes. TcIFN-Mo and IFN-Mo offspring showed a reestablished arthritic response, which remained within the range seen in controls. Immunolabeling studies on parallel groups of 90-day-infected offspring showed that the inverse CD4/CD8 cell ratio that is usually seen in lymphoid organs from these chronically infected rats (median 0.61) appeared to have recovered in the TcIFN-Mo and IFN-Mo groups (median 1.66 and 1.78, respectively) and was not different from uninfected controls (1.96). These studies indicate that early stimulation with IFN-gama is able to reverse the immunosuppressive state that is usually present during the chronic period of the experimental infection.

Macrophage activity, IL-6 levels, antibody response and heart histology in rats undergoing an attenuated Trypanosoma cruzi acute infection upon treatment with recombinant interferon gamma.

Earlier experiments in Trypanosoma cruzi-infected rats showed that recombinant rat (Rr) interferon (IFN)-gamma given shortly after infection ameliorated acute disease without modifying the serum titers of endogenously synthesized IFN-gamma and tumor necrosis factor. To gain some insight into the processes underlying this protective effect, 21-day old 'I' rats that were infected with T. cruzi and the following day started with a 20-day cycle of RrIFN-gamma injections (20000 IU/rat/day) were investigated for the in vitro replication of T. cruzi and nitric oxide (NO) production by peritoneal macrophages (day 7 post-infection, pi), antibodies with lytic activity against T. cruzi (days 7, 20, and 28 pi), and serum levels of biologically active interleukin (IL)-6 (days 15 and 30 pi). Therapy with RrIFN-gamma rendered cultured peritoneal macrophages less permissive to infection with T. cruzi. Such an effect was not accompanied by higher amounts of NO in macrophage cultured supernatants, compared with those from T. cruzi-infected rats receiving no RrIFN-gamma, which appeared not to be protected from in vitro infection. Acutely T. cruzi-infected rats had significant amounts of IL-6 in their sera - this not being the case in infected rats given RrIFN-gamma, whose levels appeared decreased as in control rats. The presence of complement-mediated anti-T. cruzi lytic antibodies was not modified by RrIFN-gamma. Likewise, heart histology at day 7 pi revealed that treatment with RrIFN-gamma made no differences as to the amount of acute inflammation, but tended to reduce the myocardial parasite load.

Protection of young rats from acute Trypanosoma cruzi infection by interferon-gamma given to their mothers during pregnancy.

We investigated whether administration of interferon-gamma (IFN-gamma) to pregnant rats, infected or not with Trypanosoma cruzi, was likely to protect their offspring from trypanosomal infection. Upon mating with syngeneic sires, four groups of 70-day-old female 1 rats were subjected to one of the following procedures: treatment with recombinant rat (Rr)IFN-gamma 50,000 IU/rat five times/week for three weeks; infection with 1 x 10(6) trypomastigotes of T. cruzi at 7, 14, and 21 days after mating plus IFN-gamma treatment as given to the former group; the same protocol but IFN-gamma injections being replaced by injection with physiologic saline. Offspring were nursed by their mothers until weaning and then infected with a similar dose of T. cruzi. Pregnant rats showed no exacerbated infection but a self-resolving mild disease, regardless of whether or not they had received IFN-gamma. Maternal infection with T. cruzi and/or IFN-gamma treatment did not affect gestational outcome. Offspring born to both groups of IFN-gamma-treated mothers were almost fully protected from acute infection, and showed higher levels of anti-T. cruzi IgG antibodies when compared with young born to their respective IFN-gamma-untreated mothers. Measurements of IFN-gamma serum activities indicated that ameliorated acute disease in offspring whose mothers were given IFN-gamma during gestation, was not associated with increased levels of endogenously produced IFN-gamma.

Chronic Trypanosoma cruzi infection in the rat: cyclophosphamide-induced recovery of adjuvant arthritis correlates with changes in the levels of lymph node T-lymphocytes and class II+ cells.

We have previously reported that treatment with cyclophosphamide (Cy) reversed the partial resistance of chronically Trypanosoma cruzi-infected rats to adjuvant-induced arthritis (AA) and caused a slight enhancement of arthritis in controls, when given 48 h before induction. To ascertain whether this Cy effect could be associated with regional changes of immunocompetent cells, popliteal lymph nodes were studied for their T-cell subsets and cells carrying class II major histocompatibility (MHC) antigens (1-A and 1-E molecules). Analysis at the time of arthritis induction revealed that infected rats receiving Cy 48 h earlier appeared to have recovered from the inverse balance of major T-cell subsets and showed 1-E+ cells lowered to normal, whereas values from control rats remained unchanged by Cy treatment. Establishment of AA was associated with substantial changes in the phenotype of lymph node cells that drained the affected limb. Changes were equally recorded in control and infected arthritic rats, and consisted of a significant raise of CD4+ and I-A+ cells along with lowered numbers of CD8+ and I-E+ cells. Treatment with Cy lowered even further the levels of CD8+ cells, while causing no affectation in the number of CD4+ cells that remained increased as in the arthritic counterparts receiving no Cy. Comparative analysis of class II MHC+ cells in Cy-treated rats revealed an additional decrease of I-E+ cells in draining lymph nodes from infected and control rats, which coincided with a simultaneous increase in I-A+ cells in the uninfected group. It is suggested that a deletion of a regulatory T-cell subset as well as an improved presentation of arthritogenic peptides may at least underlie the Cy-induced enhancement of the arthritic response.

[Concomitant immunity against Sarcoma E 100 comparing 2 strains of rats]. / Inmunidad concomitante contra el Sarcoma E 100 comparando dos líneas de ratas.

Concomitant immunity (IC) is usually defined as the capacity of any animal bearing a progressor tumor to inhibit a second challenge with the same tumor. In order to establish the contribution of the host to the origin of this phenomenon, IC was induced in two lines of rats with a different behavior when challenged with Sarcoma E 100 (SE 100), i.e., line IIMc: 90% take and 100% regression; line "m": 100% take and death. The rats received a second challenge on day 3 (Group II), 7 (III), and 14 (IV), as well as the control groups: II', III' and IV', respectively. The animals reinoculated on day 7 showed a decrease, both in percentage of takes (Fig. 1, III vs III') and tumor surface (Table 1, 2). Likewise, in rats IIMc, a lesser development of the first inoculum (Table 1, Ia vs I') was observed. The Winn assay (Table 3) confirmed the presence of immunocompetent spleen cells (CE) against SE 100 in IIMc rat spleens: namely, 1) immune rats (II), 2) unique tumor bearing rats (IV), 3) first progressor and second negative inoculum (V). In line "m" the percentage of takes was only smaller in the group inoculated conjointly with CE from immune rats (Table 3, VI vs VII). A mere 10% (3/30) of "m" rats were immunized against SE 100. Consequently, these results could attribute the IC, in IIMc rats, to immunological mechanisms, while in "m" it could be due to factor(s) released and/or induced by the first tumor, as proposed by Gorelik.

Inmunidad concomitante contra el Sarcoma E 100 comparando dos líneas de ratas. / [Concomitant immunity against Sarcoma E 100 comparing 2 strains of rats]

Concomitant immunity (IC) is usually defined as the capacity of any animal bearing a progressor tumor to inhibit a second challenge with the same tumor. In order to establish the contribution of the host to the origin of this phenomenon, IC was induced in two lines of rats with a different behavior when challenged with Sarcoma E 100 (SE 100), i.e., line IIMc: 90

take and 100

regression; line [quot ]m[quot ]: 100

take and death. The rats received a second challenge on day 3 (Group II), 7 (III), and 14 (IV), as well as the control groups: II, III and IV, respectively. The animals reinoculated on day 7 showed a decrease, both in percentage of takes (Fig. 1, III vs III) and tumor surface (Table 1, 2). Likewise, in rats IIMc, a lesser development of the first inoculum (Table 1, Ia vs I) was observed. The Winn assay (Table 3) confirmed the presence of immunocompetent spleen cells (CE) against SE 100 in IIMc rat spleens: namely, 1) immune rats (II), 2) unique tumor bearing rats (IV), 3) first progressor and second negative inoculum (V). In line [quot ]m[quot ] the percentage of takes was only smaller in the group inoculated conjointly with CE from immune rats (Table 3, VI vs VII). A mere 10

(3/30) of [quot ]m[quot ] rats were immunized against SE 100. Consequently, these results could attribute the IC, in IIMc rats, to immunological mechanisms, while in [quot ]m[quot ] it could be due to factor(s) released and/or induced by the first tumor, as proposed by Gorelik.