Immune reactions in acute viral hepatitis.

Serial studies of PHA-induced lymphocyte transformation, serum autoantibodies, immunoglobulins and complement were performed in seventeen patients with hepatitis A and nine patients with hepatitis B. In both types of hepatitis PHA-induced transformation was markedly impaired during the 1st week after the onset of jaundice and there was less marked but prolonged impairment for a further period of 6-10 weeks. A group of eleven subjects with a previous history of hepatitis had values which were similar to those of healthy persons. Serum from patients with hepatitis A and hepatitis B contains an inhibitor of lymphocyte response to PHA. The inhibitor depresses the function of both patients' and normal lymphocytes and is only detectable during the acute phase of the illness. Washing lymphocytes free from autologous serum did not restore the PHA response to normal but the markedly impaired response present during the first 2 weeks of the illness was improved. A serum factor or factors may therefore be responsible for at least part of the impaired response of lymphocytes to PHA during the acute phase of hepatitis but does not appear to account for the more prolonged impairment of the PHA response. The protracted lymphocyte defect is possibly induced by hepatitis virus. The incidence of autoantibodies and the changes in immunoglobulin levels were similar to those reported by other workers.     

Immune reactions and long-term therapy with human leukocyte interferon

Twenty patients with osteosarcoma were treated with exogenous human leukocyte interferon for periods ranging from 6 to 18 months. Eleven of them remained free from detectable tumour growth during this treatment. Blood samples from all patients were tested for antibodies against interferon and against impurities in the interferon preparations. No patient developed detectable levels of neutralizing antibodies against interferon. All patients formed antibodies against contaminants in the concentrated crude interferon and the partially purified interferon preparation which had been used for treatment.     

Immune reactions in a changing environment. USA initiatives

Environmental hazards occurring as an undesirable consequence of economic progress, urbanization and pollution have become a worldwide concern. In the US, this is evident from the campaign against smoking which has focused attention on the lung in part because the lung as a target organ is constantly exposed to many visible environmental hazards. On the other hand, environmental hazards which are not lethal, but cause their effects in an insidious fashion, may be difficult to study and identify. Among the disciplines available to assess adverse health consequences of xenobiotics ('strange' substances in our environment), application of modern immunological methods in concert with traditional toxicologic studies have to date demonstrated significant progress in drug allergy, food allergy, environmentally induced lung diseases and autoimmunity. These successes have come from the collaboration of immunologists, allergologists, pulmonologists, pharmacologists and toxicologists. In fact, a newer discipline of immunotoxicology has emerged in order to deal with these complex issues. The National Institutes of Health, through a series of workshops and research initiatives, and in collaboration with other US government agencies, including the Environmental Protection Agency, the National Institute of Environmental Health Sciences, and the National Academy of Sciences, is attempting to foster research aimed at enhancing progress in the field of immunotoxicology. The overall aim is to encourage the use of modern immunologic approaches to the study of the alleged harmful effects of xenobiotics on the immune system. Success will permit the development of improved diagnostic tools followed by initiatives concerned with prevention. Apart from their scientific implications the results are expected to have an impact on social, legal and economic issues within society.     

Excretory-secretory and somatic antigens in the diagnosis of human filariasis.

In order to compare the immunodiagnostic value of excretory-secretory (E-S) antigens derived from adult Brugia malayi worms with somatic antigens derived from adults, microfilariae (Mf) and infective larvae (L3) of these parasites, well defined serum pools from patients with filarial (brugia, bancrofti, loa and perstans) and non-filarial (ascaris, stronglyoides, toxocara, echinococcus, cysticercus and schistosoma) helminth infections were tested against antigens derived from these different life cycle stages of B. malayi in a Staphylococcus aureus radioimmunoprecipitation assay (S. aureus RIA). The adult brugia antigens proved significantly more discriminatory than those of the other parasite stages, with the homologous brugia serum pool also showing greater reactivity to adult than to L3 and Mf antigens. Similar results were obtained when individual sera from patients (rather than serum pools) were tested in the same assay. The most surprising finding was the minimal reactivity seen between the adult filarial antigens and the non-filarial serum pools despite the presence in these pools of strong antibody reactivity with their homologous antigens. The reasons underlying the unexpected specificity of this S. aureus RIA for discriminating among sera from filarial and non-filarial infections were analysed qualitatively by immunoprecipitation techniques. It was found that use of the chloramine-T method for radioiodination resulted in preferential labelling of the low molecular weight (mol. wt) proteins (10-70,000 daltons) in the B. malayi adult somatic antigen and that these antigens were bound primarily by the filarial and not the non-filarial serum pools. These findings suggest that lower mol. wt helminth antigens may show greater species specificity than those with higher mol. wt, and those with higher mol. wt, greater cross-reactivity. If substantiated by further analysis, such results would have important implications for the subsequent isolation of diagnostically important filarial parasite antigens.     

Specific cellular immune unresponsiveness in human filariasis

In an effort to identify factors important in the pathogenesis of filarial disease, studies of the cellular and humoral immune responses to the parasitic nematode Wuchereria bancrofti were carried out on thirty-nine individuals in a region of the Pacific where filariasis is endemic.

Blood lymphocytes from twenty-six patients with chronic filariasis (especially that associated with persistent microfilaraemia) gave only minimal responses to filarial antigens when challenged in vitro in a lymphocyte transformation assay. In contrast, brisk responses to these same antigens were elicited in cultures of cells from a control population of thirteen exposed but not infected individuals living in the same area, the greatest responses being found in uninfected children less than 10 years old. The poor cellular responsiveness of infected individuals was filaria antigen-specific, as reactivity to tuberculin (PPD) and streptococcal (SK—SD) antigens was normal and equal in all groups. Furthermore, the immunologic deficit was limited to cell-mediated immune responses and appeared unchanged 2 weeks after treatment of the patients with the anti-filarial drug diethylcarbamazine.

We interpret our findings as evidence for a state of antigen-specific cellular unresponsiveness in patients with this chronic parasitic infection and speculate that this immunologic deficit may be of fundamental importance in the pathogenesis of filarial disease.

     

Immune reactions in different mouse strains

The responses of immunocompetent cells to thymus-dependent antigen differ in mice of different strains. Immunization stimulated phagocytic activity of peritoneal macrophages in CBA/CaLac, DBA/2, and BALB/c mice and suppressed it in CC57W mice. By the formation of antibody-producing cells in the spleen in response to thymus-dependent antigen DBA/2 and CBA/CaLac mice can be classified as high responders, BALB/c mice as medium-responders, and C57Bl/6 and CC57W mice as low responders.     

Antibodies in human filariasis sera react with diethylcarbamazine

We demonstrate by an ELISA the presence of antibodies in human filarial sera that react with diethylcarbamazine (DEC); they appear to be primarily filarial antibodies cross-reacting with DEC skeleton, since affinity-purified DEC antibodies strongly react with Wuchereria bancrofti microfilariae. These observations indicate a possible antigenic mimicry between the drug and some parasite component.     

Immune reactions to Listeria monocytogenes in the brain

Listeria monocytogenes (LM) is a common pathogen of cerebral infections. Experimental studies in mice have revealed that epithelial cells of the choroid plexus, ependymal cells, macrophages/microglia, and neurons are the target cells of LM. For the intracerebral pathogenesis of LM cell-to-cell spread via phospholipase C was particularly important. However, phospholipase C-deficient LM were not completely attenuated and, therefore, other virulence factors may also contribute to the intracerebral spread of LM. In general, all mice suffering from cerebral listeriosis rapidly succumbed to the disease. Active systemic immunization prior to intracerebral infection reduced the mortality rate to 40%. The favorable prognosis of immunized mice correlated with a reduced intracerebral bacterial load, an increased recruitment of protective CD4+ and CD8+ T cells as well as an upregulated mRNA production of protective cytokines.     

Protective immunity in human lymphatic filariasis: problems and prospects

Human filariasis caused by lymphatic dwelling nematodes, affecting 120 million persons worldwide, is a major public health problem. Efforts towards development of vaccines for such large tissue-dwelling nematodes depends significantly on identification and demonstration of protective immunity in the exposed population. Immunological studies conducted in human filariasis so far are essentially attempts to establish a correlation of the immune response phenotypes with presence or absence of filarial infections/disease in the host, and the cause-effect relationship between the observed immune responses in the host and protective immunity continues to be conjectural. This short review attempts to clarify the functional definition of protective immunity, problems associated with identification of putatively immune subjects in endemic areas, role of antibodies reactive to surface of microfilariae and larvae stages of filarial parasites and importance of undertaking immunological investigations on a longitudinal basis in different cohorts of subjects presenting with one or the features of infection and/or disease for more accurate delineation of protective immunity in human filariasis.     

Antibody-dependent cell-mediated effects in bancroftian filariasis.

The nature of immunoglobulin and effector cells involved in the antibody-dependent cell-mediated adhesion and cytotoxicity to Wuchereria bancrofti larvae has been investigated. Human neutrophils and eosinophils purified from peripheral blood by metrizamide gradients readily adhered to the parasites in presence of IgG fraction of sera from majority of elephantiasis cases with amicrofilaraemia and many of the endemic normals. The cells from normal, microfilariae and elephantiasis cases were equally effective inthe adhesion reaction. While the adhered neutrophils killed the larvae, eosinophils were ineffective in this respect. DEC treatment of elephantiasis cases results in a significant reduction in the ability of their sera to promote cellular adhesion.     

Identification of circulating parasite acetylcholinesterase in human and rodent filariasis

In the present study, the enzyme acetylcholinesterase (AChE) from filarial parasites was identified in sera from humans infected withOnchocerca volvulus as well as inMastomys natalensis infected withBrugia pahangi. The enzyme was present in immune complexes precipitated with cold 4% polyethylene glycol. The infected sera showed 3–4 times more AChE activity than did normal sera, and enzyme activity could be demonstrated in 5% polyacrylamide gels by specific staining. The enzyme from infected serum showed 3 times more activity when acetylthiocholine was used as the substrate as compared with butyrylthiocholine, whereas the enzyme activity present in normal serum was low and did not show this substrate specificity. Immunoprecipitation assays confirmed the presence of anti-AChE antibodies in the infected serum. The enzyme was further analysed by enzyme-linked immunosorbent assay and immunoblotting with rabbit antibodies toB. malayi AChE. Immunoblotting of theB. pahangi-infected serum revealed two closely located bands at about 200 kDa and one 95-kDa band, whereas inO. volvulus-infected serum, only one specific band was observed at about 200 kDa. The identification of parasite AChE may be particularly useful for diagnosis of the disease or for the study of the involvement of this enzyme in the host-parasite relationship.     

Circulating immune complexes in experimental filariasis.

Circulating immune complexes have been investigated in jirds (Meriones unguiculatus) infected with the filarial nematode Brugia pahangi. Two-month-old male jirds were inoculated with seventy-five B. pahangi infective larvae into the left groin. At 8 months post-infection, sera of individual animals from a group of seventeen infecteds and seventeen age-matched controls were analysed for immune complexes by (1) a solid-phase C1q binding assay (Clq-SP) and (2) precipitation with 3.5% polyethylene glycol followed by binding of 125I-labelled rabbit anti-jird Ig antiserum (PEG). A significant increase in the level of circulating immune complexes was shown in the infected group as compared with the controls for both assays, with a P value = 0.005 for PEG and P = 0.001 for Clq-SP. Using the mean of the control group +/- 2 s.d. as the upper limit of the normal range, 24% of the infected group had elevated immune complex levels by the PEG assay, and 41% were elevated in the C1q-SP assay. A high degree of variability was noted in the levels of immune complexes among individual animals in the infected group by each test. No correlation between immune complex levels and numbers of circulating microfilariae was found in either assay.     

IgE antibodies are more species-specific than IgG antibodies in human onchocerciasis and lymphatic filariasis.

To explore the relative species specificities of the IgE and IgG antibody responses to helminth infections in man, we studied four pools of sera from patients infected with Wuchereria bancrofti, Brugia malayi, Onchocerca volvulus or Ascaris lumbricoides and ten individual sera from patients with onchocerciasis. IgE antibodies were detected by radioallergosorbent test (RAST) analysis and IgG antibodies by a Staphylococcus protein A radioimmunoassay (Staph A-RIA). Analysis of the binding curves with four different immunosorbents (prepared from antigens of B. malayi, O. volvulus, Dipetalonema viteae and A. lumbricoides) in the RAST and the binding curves with these same four antigens in the Staph A-RIA confirmed the relative species specificities for both the IgE and IgG antibody responses. Then determination of these antibody levels after specific absorption of the sera with both homologous and heterologous antigens showed that in all instances there was significantly less cross-reactivity with heterologous parasite antigens (i.e. higher species specificity) in the IgE antibody response to filarial infection than in the corresponding IgG antibody response. Such findings imply that efforts toward developing techniques for specific immunodiagnosis of filarial infections are likely to be particularly successful if focused on the IgE antibody response of exposed individuals.