G Del Prete

Purified protein derivative of Mycobacterium tuberculosis and excretory-secretory antigen(s) of Toxocara canis expand in vitro human T cells with stable and opposite (type 1 T helper or type 2 T helper) profile of cytokine production.

A large series of T cell clones (TCC) specific for purified protein derivative (PPD) of Mycobacterium tuberculosis (total 60) or Toxocara canis excretory/secretory (TES) antigen (total 69) were established from the peripheral blood of two healthy individuals and analyzed for their profile of cytokine production in response to stimulation with either the specific antigen or the polyclonal activator phorbol myristate acetate plus anti-CD3 antibody. Under both these experimental conditions, the great majority of PPD-specific TCC secreted IL-2 and IFN-gamma but not, or limited amounts of, IL-4 and IL-5. In contrast, most TES-specific TCC secreted IL-4 and IL-5 but not, or limited amounts of, IL-2 and IFN-gamma. PPD-specific TCC that failed to secrete IL-4 and IL-5, and TES-specific TCC that failed to secrete IL-2 and IFN-gamma, were found to lack transcripts for IL-4 and IL-5, or for IL-2 and IFN-gamma, respectively. During the course of the study, over a 6-mo period, the functional phenotype of both TES- and PPD-specific TCC was repeatedly assessed and remained constant. These data demonstrate that T cells with stable Th1 or Th2 functional pattern exist not only in mice but also in humans and suggest that in the course of natural immunization certain infectious agents preferentially expand T cell subsets with stable and definite profile of cytokine production.

Different cytokine profiles of intraphepatic T cells in chronic hepatitis B and hepatitis C virus infections

BACKGROUND & AIMS The cytokine pattern secreted by T cells at the site of viral replication may influence the final outcome of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections. The aim of this study was to assess whether a cytokine imbalance oriented toward T helper (Th) 1 or Th2-type responses may play a role in chronic hepatitis B or C. METHODS Production of interferon (IFN)-gamma, interleukin (IL)-4, and IL-5 by wide series of T-cell clones derived from the liver of 6 patients with chronic hepatitis B (291 clones) and 9 patients with chronic hepatitis C (260 clones) was studied. T-cell clones were generated by limiting dilution from freshly isolated mononuclear cells derived from liver tissue to give a reliable representation of the intrahepatic inflammatory infiltrates. RESULTS The majority of liver-infiltrating T cells in chronic hepatitis C were Th1 cells able to secrete IFN-gamma but unable to secrete IL-4 or IL-5, whereas in hepatitis B, most CD4+ and CD8+ liver T cells were ThO-like cells able to produce not only IFN-gamma but also IL-4 and IL-5. CONCLUSIONS The different cytokine profiles of T cells within the liver in chronic HBV and HCV infections illustrate a different behavior of the local immune response in these two infections that may have pathogenetic implications.

Long-lasting memory T cell responses following self-limited acute hepatitis B.

The molecular and cellular basis of long-term T cell memory against viral antigens is still largely undefined. To characterize anti-viral protection by memory T cells against non-cytopathic viruses able to cause acute self-limited and chronic infections, such as the hepatitis B virus (HBV), we studied HLA class II restricted responses against HBV structural antigens in 17 patients with acute hepatitis B, during the acute stage of infection and 2.2 to 13 yr after clinical resolution of disease. Results indicate that: (a) significant T cell proliferative responses to HBV nucleocapsid antigens were detectable in all patients during the acute phase of infection and in 14/17 also 2-13 yr after clinical resolution of disease; b) long-lasting T cell responses were sustained by CD45RO+T cells, predominantly expressing the phenotype of recently activated cells; c) limiting dilution analysis showed that in some patients the frequency of HBV-specific T cells was comparable to that observed in the acute stage of infection and, usually, higher than in patients with chronic HBV infection; d) the same amino acid sequences were recognized by T cells in the acute and recovery phases of infection; and e) HBV-DNA was detectable by nested-PCR in approximately half of the subjects. to conclusion, our results show that vigorous anti-viral T cell responses are detectable in vitro several years after clinical recovery from acute hepatitis B. Detection of minute amounts of virus in some recovered subjects suggests that long-term maintenance of an active anti-viral T cell response could be important not only for protection against reinfection but also for keeping the persisting virus under tight control.

HUMAN TH1 AND TH2 LYMPHOCYTES: THEIR ROLE IN THE PATHOPHYSIOLOGY OF ATOPY

In human beings, as in mice, two distinct patterns of cytokine secretion have been defined among CD4 + helper T‐cell clones. Human type 1 helper (Th1), but not type 2 helper (Th2), cells produce interleukin‐2 (IL‐2), gamma‐interferon (IFN‐γ), and tumor necrosis factor‐β, whereas Th2, but not Th1, cells secrete IL‐4 and IL‐5, but not IL‐2 or IFN‐γ. Other cytokines, such as IL‐3, IL‐6, GM‐CSF, or TNF‐α, are produced by both Th1 and Th2 cells. The cells, a third Th subset, show combined production of Th1‐and Th2‐type cytokines. The different cytokine patterns are associated with different functions. In general, Th2 cells provide an excellent helper function for B‐cell antibody production, particularly of the IgE class. On the other hand, Th1 cells are responsible for delayed type hypersensitivity reactions and are cytolytic for autologous antigen‐presenting cells, including B cells. Most allergen‐ or helminth‐antigen‐specific human CD4 + T‐cell clones exhibit a Th2 phenotype, whereas most clones specific for bacterial antigens show a Th1 profile. Allergen‐specific Th2 cells seem to play a crucial role in atopy. These cells induce IgE production via IL‐4 and favor the proliferation, differentiation, and activation of eosinophils via IL‐5. In addition, Th2‐derived IL‐3 and IL‐4 are mast‐cell growth factors that act in synergy, at least in vitro. Recent evidence indicates that allergen‐specific Th2 cells are selectively enriched in tissues affected by allergic inflammation, such as the bronchial mucosa of subjects with allergic asthma. However, the reason why allergens preferentially expand Th2 cells in atopics is unknown. A number of factors may influence Th subset differentiation into Th1 or Th2 cells. At present, the IL‐4 produced in the microenvironment in which antigen is presented to Th cells seems to be the major factor favoring Th2 development. In this connection, the aberrant production of IL‐4 (and IL‐5) exhibited by T cells from atopics, even in response to bacterial antigens, may be of great importance.

Atopy, intestinal helminth infection and total serum IgE in rural and urban adult Gambian communities

Background The rarity of atopy in traditional societies has been attributed to high parasite‐driven blocking IgE concentrations. Information is lacking on the relationship between atopy, IgE and intestinal helminth infection in African populations.

Recombinant interferon-alpha selectively inhibits the production of interleukin-5 by human CD4+ T cells.

The effects of recombinant IFN-alpha on the production of IL-5 by human CD4+ T cells were first analyzed on resting CD4+ T cells purified from normal PBMC and stimulated either with a combination of PMA and anti-CD28 mAb or anti-CD3 mAb cross-linked on B7-1/CD32-transfected mouse fibroblasts. We found that IFN-alpha profoundly inhibited in a dose-dependent manner IL-5 production by resting CD4+ T cells whereas IL-10 was upregulated in both systems. The addition of a neutralizing anti-IL-10 mAb to PMA and anti-CD28 mAb upregulated IL-5 production by resting CD4+ T cells but did not prevent IFN-alpha-induced IL-5 inhibition. We then analyzed the effect of IFN-alpha on the production of cytokines by differentiated type 2 helper (Th2) CD4+CD3- cells isolated from peripheral blood of two patients with the hypereosinophilic syndrome. In both cases, IFN-alpha markedly inhibited IL-5 production while it induced mild upregulation of IL-4 and IL-10. Finally, the inhibitory effect of IFN-alpha on IL-5 production was confirmed on a panel of Th2 and Th0 clones generated in vitro. In 2 out of 6 clones, IL-5 inhibition was associated with upregulation of IL-4 and IL-10. We conclude that IFN-alpha selectively downregulates IL-5 synthesis by human CD4+ T cells.

CD30 and type 2 T helper (Th2) responses.

CD30 is one of the members of the tumor necrosis factor receptor superfamily, originally described as a marker of Reed‐Sternberg and Hodgkins cells in Hodgkins lymphoma. CD30 appears to be preferentially expressed on, and its soluble form (sCD30) released by, CD4+ and CD8+ T cell clones capable of producing T helper 2 (Th2)‐type cytokines. In nonneoplastic conditions, CD30+ T cells are barely detectable in vivo; however, a few allergen‐specific CD4+CD30+ T cells inducible to the production of Th2‐type cytokines could be sorted out from the circulation of allergic subjects after allergen exposure. Moreover, high numbers of CD30+ T cells were found in the lymph node of a patient suffering from Omenns syndrome, a rare congenital Th2‐mediated immunodeficiency disorder. More importantly, high serum levels of sCD30 were observed in some conditions in which a pathogenetic role for Th2 cells has been suggested, such as Omenns syndrome, atopy, systemic lupus erythematosus, and after infection with measles virus or human immunodeficiency virus. Thus, detection of CD30+ T cells and/or of increased levels of sCD30 may reflect the presence of immune responses or immune alterations characterized by the prevalent activation of Th2‐like cells. J. Leukoc. Biol. 57: 726‐730; 1995.

Airway eosinophilia and expression of interleukin-5 protein in asthma and in exacerbations of chronic bronchitis

Background An increased nutnber of eosinophils in the bronchial mucosa has been demonstrated both in asthma and in exacerbations of chronic bronchitis. Oiyective To investigate whether the airway eosinophilia present in asthma and in chronic bronchitis during exacerbations is associated with interleukin (IL)‐5 protein expression in the bronchial mucosa.

Defective in vitro production of gamma-interferon and tumor necrosis factor-alpha by circulating T cells from patients with the hyper-immunoglobulin E syndrome.

Circulating T cells from four patients with the hyper-IgE syndrome were found to produce significantly lower concentrations of interferon-gamma (IFN-gamma) in response to stimulation with phytohemagglutinin (PHA) than did T cells from eight age-matched healthy controls, three patients with atopic dermatitis and one patient with chronic granulomatous disease. A clonal analysis revealed that patients with hyper-IgE syndrome had markedly lower proportions of circulating T cells able to produce IFN-gamma and tumor necrosis factor-alpha (TNF-alpha) in comparison with controls. In contrast, the proportions of peripheral blood T cells able to produce IL-4 or IL-2 were not significantly different in patients and controls. All the four patients with hyper-IgE syndrome showed high proportions of circulating CD4+ helper T cells able to induce IgE synthesis in allogeneic B cells, as well. Such an activity for IgE synthesis appeared to be positively correlated with IL-4 production by T cells and inversely related to the ability of the same T cells to produce IFN-gamma. Since IFN-gamma exerts an inhibitory effect on the synthesis of IgE and both IFN-gamma and TNF-alpha play an important role in inflammatory reactions, we suggest that the defective production of IFN-gamma may be responsible for hyperproduction of IgE and the combined defect of IFN-gamma and TNF-alpha may contribute to the undue susceptibility to infections seen in patients with hyper-IgE syndrome.

In vivo CD30 expression in human diseases with predominant activation of Th2-like T cells.

CD3O is a member of the tumor necrosis factor (TNF) receptor family, originally described as a marker for Hodgkin and Reed‐Sternberg cells in Hodgkins disease, which has been found to be preferentially expressed by T cells producing Th2‐type cytokines. The presence of CD3O expression was assessed by both immunohistochemistry and reverse transcriptase‐polymerase chain reaction in the target organs of patients with Th1‐ or Th2‐dominated disorders. CD3O expression was found in neither the gut of patients with Crohns disease nor in the gastric antrum of Helicobacter pylori‐infected patients, where there was high interferon‐γ (IFN‐γ) expression. In contrast, high CD3O expression in the apparent absence of IFN‐γ expression was observed in the skin of patients with systemic sclerosis or chronic graft versus host disease (GVHD), which can be considered Th2‐dominated disorders. Moreover, high levels of soluble CD3O were found in the serum of both systemic sclerosis and GVHD patients but not in the serum of patients suffering from multiple sclerosis, a Th1‐dominated disorder. Thus, CD3O expression appears to be preferentially associated with Th2‐type responses not only in vitro but also in vivo. J. Leukoc. Biol. 61: 539–544; 1997.