T lymphocyte lines isolated from atheromatous plaque contain cells capable of responding to Chlamydia antigens.

Chlamydia pneumoniae infection is associated with atherosclerosis and the organism has been identified in arterial lesions. To determine whether T lymphocyte-mediated immune responses to Chlamydia antigens within plaque could contribute to pathogenesis, we have derived T cell lines from atherosclerotic plaques of 32 patients. Culture with IL-2 alone proved insufficient for cellular activation and expansion, but additional stimulation with phytohaemagglutinin (PHA) or recall antigens allowed consistent establishment of T cell lines. Furthermore, in cultures of approx. 500 tissue fragments, Chlamydia organisms proved as effective as other recall antigens in producing outgrowth of arterial T cells (20-25% wells produced T cell lines). Testing the antigen responsiveness of T cell lines showed that those derived using Chlamydia organisms were more likely to respond to Chlamydia (5/29+) than those isolated using other stimuli (6/69+ for PHA; 5/57+ for PPD and tetanus toxoid (TT)). However, lines responsive to each of the recall antigens were observed. Using recombinant Chlamydia antigens, some Chlamydia-specific T cell lines were shown to respond to OMP2 and/or hsp60. Those recognizing Chlamydia hsp60 did not cross-react with human hsp60, but human hsp60-responsive lines were also observed. Thus, atherosclerotic plaque tissue contains a variety of memory T lymphocytes, and amongst these are cells capable of recognizing Chlamydia antigens. In a C. pneumoniae-infected plaque, such T cells may be activated by local antigen and could contribute to the inflammatory process in the arterial wall through CD40 ligand expression and cytokine secretion.

Immune responses to Chlamydia antigens in atherosclerosis.

Aim of this study was to isolate T lymphocytes from atheromatous plaques and to determine they respond to Chlamydia antigens. Atheromatous plaques from carotid endarterectomy patients, were cultured in vitro with the T cell growth factor, IL-2. This rarely allowed outgrowth of T cell lines. However, when combined with a mitogenic or antigenic stimulus to T cells, T cell lines were obtained from most patients, and from approximately 30% of replicate plaque tissue fragments. Chlamydia organisms were as effective in allowing the establishment of T cell lines as other recall antigens. T cell lines were tested for their ability to recognize antigens presented by autologous macrophages. Some lines responded to Chlamydia organisms, and also to the recombinant Chlamydia proteins hsp60 and OMP2. However, other lines recognized recall antigens. These results indicate that the atheromatous plaque contains memory T lymphocytes, and amongst the antigens they recognize are Chlamydia proteins. Stimulation of T cells was required to allow outgrowth in vitro, suggesting that the T cells were not in an activated state in vivo. However, since Chlamydia pneumoniae is present in the atheromatous plaque, activation of Chlamydia-reactive T cells by local antigen is a potential pro-inflammatory mechanism which could contribute to the pathogenesis of atherosclerosis.

Evidence that cytokine-mediated immune interactions induced by Schistosoma mansoni alter disease outcome in mice concurrently infected with Trichuris muris.

In murine models of Schistosoma mansoni infection, egg production is associated with a switch from T helper cell (Th)1- to Th2-type responses to both schistosome-specific and unrelated antigens. Polyparasitism is common in human populations within S. mansoni endemic areas. We have, therefore, examined whether coinfection with S. mansoni could affect the outcome of a second parasitic infection, through Th2 cytokine-dependent modifications to the host immune response. We find that when mice susceptible to infection with the gut nematode Trichuris muris are coinfected with S. mansoni, they acquire the capacity to resolve T. muris infection, thus demonstrating a resistant phenotype. This ability to expel T. muris is associated with the production of Th2-associated cytokines, and corresponding antibody isotypes, in response to S. mansoni egg antigens. The Th2 response shows that there is no compartmentalization between spleen and mesenteric lymph nodes, and that the expulsion of T. muris is not caused by any changes in the host intestine associated with excretion of schistosome eggs. This influence of schistosome infections may be important, not only for the outcome of infections with unrelated pathogens in endemic areas, but also for the efficacy of vaccines in such areas.

Deficient expression of co-stimulatory molecules on Leishmania-infected macrophages.

Co-stimulatory signals are necessary for the full activation of T cells for growth and effector function. As co-stimulatory molecules are normally regulated in their expression, it has been suggested that microorganisms enhance their expression on host antigen-presenting cells (APC), thus allowing efficient generation of anti-microbial immunity. We here describe experiments which demonstrate that infection of macrophages, both in vitro and in vivo, by the protozoan parasite Leishmania donovani fails to trigger expression of co-stimulatory molecules B7-1 and heat-stable antigen on these APC. Furthermore, infection with this parasite inhibits the macrophage response to normal regulatory signals, such as bacterial lipopolysaccharide. These changes in the cell surface are mirrored in functional studies of co-stimulation in vitro. Together, these data suggest a further facet of parasite interference in host immunity, but also indicate a potential new target for immunotherapy.

Cell-mediated responses of immunized vervet monkeys to defined Leishmania T-cell epitopes.

A population of vervet monkeys was immunized with killed parasites and infected with Leishmania major promastigotes either by needle or by infected-fly bite. The responses of recovered monkeys to mitogens, killed parasites, and molecularly defined T-cell epitopes were then compared with those of control animals. Peripheral blood mononuclear cells (PBMC) from both naive and recovered animals proliferated strongly in response to both B- and T-cell mitogens, although the responses of the recovered animals were less strong than those of the naive animals. Cells from recovered vervets, but not those from naive vervets, also proliferated in response to parasite antigens and synthetic T-cell epitopes. Likewise, cells from recovered animals released gamma interferon and either interleukin 2 (IL-2) or IL-4 into culture media in response to both of the above-mentioned antigens, whereas cells from control animals did not. The fact that no IL-5 could be measured following parasite antigen or synthetic T-cell epitope stimulation of PBMC suggested that cells proliferating in response to these molecules belonged to the Th1 subset. Phenotypic analysis of the PBMC showed a marked increase in T-cell but not B-cell populations in recovered animals. Among this population was an increased number of CD45R0+ memory cells. The data from this study are in keeping with the earlier finding that vervet monkeys provide an excellent model system for leishmaniasis. Further, these data support the contention that synthetic T-cell epitopes are prime candidates for molecularly defined Leishmania vaccines.

Immunity and morbidity in human schistosomiasis mansoni.

This paper reviews the results of a longitudinal, multidisciplinary study on schistosomiasis mansoni that has been in progress in Machakos District, Kenya, since 1980. Different methods of delivering chemotherapy have been compared in a medium scale operational control programme. It is concluded that treatment only of infected children is an effective and feasible means of control, the frequency of treatment depending on the severity of disease. Within the framework of this programme, detailed studies have been undertaken of immunity to reinfection after treatment and of the reasons for differences in observed morbidity between different areas. An apparent resistance to reinfection, especially in older individuals, may be attributable to the protective effect of IgE antibodies against adult worm antigens. Various factors other than intensity of infection may contribute to severe morbidity, including parasite strain differences, interactions with other infections, nutritional status, and abnormalities in the regulation of pathogenic immune responses to egg antigens.

Recombinant interleukin-1 alpha augments granuloma formation and cytokine production but not parasite clearance in mice infected with Leishmania donovani.

In vivo administration of various doses of recombinant interleukin-1 alpha to B10.D2/n mice chronically infected with Leishmania donovani resulted in enhanced formation of granulomas and in vitro production of gamma interferon. By direct microscopical enumeration, reduction in gross parasite burden in the viscera was not observed, however. These data highlight an important discordance between granuloma formation per se and parasite elimination and suggest that interleukin-1 deficiency alone cannot account for the chronicity of this disease.

Differential production of Th1- and Th2-derived cytokines does not determine the genetically controlled or vaccine-induced rate of cure in murine visceral leishmaniasis.

Recent studies with models of cutaneous leishmaniasis have provoked much interest in the role of CD4+ T cell subsets in determining the outcome of infectious disease. In Leishmania major infections, cure vs progressive disease correlates with the expansion of Th1-like or Th2-like CD4+ populations, respectively. We have investigated whether similar responses are associated with the differential patterns of infection seen in models of visceral leishmaniasis, caused by L. donovani. Splenic lymphocytes from infected Lsh congenic C57BL/10 (Lshs;H-2b) and B10.L-Lshr (Lshr;H-2b) mice and MHC congenic non-curing B10.D2/n (Lshs;H-2d) mice were examined for the production of cytokines representative of these CD4+ populations (IL-2, IL-3, IL-4, IL-5, and IFN-gamma). In all three strains examined, there was no evidence for the production of Th2-restricted cytokines. In addition, levels of serum IgE were depressed during the early phase of infection, indicative of in vivo IFN-gamma production. In the non-curing B10.D2/n strain, late phase of infection was associated with the decreased ability to produce cytokines in response to Ag and not with the production of IL-4 or IL-5 in response to Ag or mitogen. Serum IgE levels were also not raised above levels seen in uninfected controls. C57BL/10 mice were vaccinated with SDS-PAGE fractionated amastigote Ag bound to nitrocellulose and cytokine levels determined at various times after infection. The protocol used for vaccination was able to induce significant modulation of the course of infection in this strain and it was clear that IFN-gamma production in vitro provided an excellent correlate of rate of cure. Occasional individuals produced low levels of IL-5 in culture in response to parasite Ag, but this did not correlate with disease progression. Together, these data suggest that over-expansion of Th2-type cells and production of their specific cytokines (IL-4 and IL-5) is not a contributing factor to the variable long term course of L. donovani infection in these strains of mice.

Antigen processing and presentation: modelling with Leishmania.

Most foreign antigens are "processed" by APC into a form in which they can bind MHC molecules and be recognised by the TCR. Functional and immuno-gold labelling studies have been used to determine the putative sites of MHC-Ag interaction following uptake of Leishmania donovani into a phagolysosome. During infection with this parasite in vivo, upregulation of class II occurs. Based on studies using scid mice, NK cells appear to contribute little to this process. During chronic infection, however, APC function is diminished in spite of high class II levels. We propose that a lack of coordinate costimulator expression may lead to subsequent loss of T cell function late in infection, by a mechanism involving the induction of T cell unresponsiveness.

Incidence of renal artery stenosis in a population having cardiac catheterization.

Patients with renovascular hypertension comprise only a small percentage of those with hypertension. In our study 102 consecutive patients who had cardiac catheterization were screened at the time of the procedure for renal artery stenosis. Only 65 (64%) of the 102 patients were hypertensive, and 14 of the total population (13.7%) had renal artery stenosis. Of these 14 patients, only five had more than 50% narrowing of the arterial lumen. By renal vein renin determination, only four of the five patients with significant renal artery stenosis had lateralizing renins. The frequency of significant renovascular hypertension does not justify the routine search for this problem during catheterization procedures, though it may be worthwhile if the patients are hypertensive. This area deserves further evaluation.