European Journal of Immunology

de Souza, Valéria Ruiz; Carreno, Marie‐Paule; Kaveri, Srinivas V.; Ledur, Annick; Sadeghi, Hoss; Cavaillon, Jean‐Marc; Kazatchkine, Michel D.; Haeffner‐Cavaillon, Nicole

doi: 10.1002/eji.1830250521pmid: 7774630

We have investigated the effects of intravenous immunoglobulin (IVIg), a therapeutic preparation of normal human polyspecific IgG, on the synthesis and release of cytokines by peripheral blood monocytes. IVIg was found to selectively induce gene transcription and secretion of interleukin‐1 receptor antagonist (IL‐1ra) and IL‐8 in cultures of normal human monocytes. The addition of IVIg to cultures of purified monocytes induced a dose‐dependent secretion of IL‐1ra and IL‐8 without stimulating the production of IL‐1α, IL‐1β, tumor necrosis factor‐α or IL‐6. The effects of IVIg required both the Fc and F(ab′)2 portions of IgG. IVIg‐induced production of IL‐8 by monocytes was enhanced by lipopolysaccharide (LPS), although LPS inhibited the secretion of IL‐1ra, suggesting that IVIg and LPS stimulate distinct intracellular pathways in monocytes. Induction of IL‐1ra and IL‐8 by IVIg was enhanced in the presence of autologous T lymphocytes. Our observations document the selectivity of the effects of IVIg on the synthesis of cytokines and cytokine antagonists by human monocytes. Induction of IL‐1ra and IL‐8 by IVIg may contribute to the anti‐inflammatory effects of immunoglobulin therapy in patients with autoimmune and systemic inflammatory disorders.

De Bruijn, Marloes L. H.; Jackson, Michael R.; Peterson, Per A.

doi: 10.1002/eji.1830250522pmid: 7539754

The strict segregation of the major histocompatibility complex (MHC) class I and class II loading pathways has been challenged by recent reports indicating that MHC class I molecules can acquire antigen in the phagocytic pathway. We now show that this alternative peptide loading pathway can be used efficiently to generate macrophages able to activate unprimed antigen‐specific cytotoxic T cells in vitro. Short peptides (8–11 residues), administered in the phagocytic pathway at nanomolar concentrations, were found to be effective in specifically activating naïve cytotoxic T lymphocytes (CTL) in vitro, but longer peptides or whole protein antigen were not. Whole protein antigen coated on beads did, however, render macrophages susceptible to lysis by an antigen‐specific CTL clone. This indicates that proteolysis in the phagocytic pathway has limited capability for class I‐restricted presentation. We propose a model for class I loading in the phagocytic pathway consisting of direct trafficking of nascent MHC class I from the trans‐Golgi network to the phagosome, prior to appearance at the cell surface, and the use of the narrow cavity between bead and phagosomal membrane as a peptide exchange/loading compartment. Targeting immunogenic class I‐binding peptide to the phagocytic pathway of macrophages facilitates presentation in association with class I. This is a useful tool for CTL response induction in vitro.

Öhlén, Claes; Höglund, Petter; Sentman, Charles L.; Carbone, Ennio; Ljunggren, Hans‐Gustaf; Koller, Beverly; Kärre, Klas

doi: 10.1002/eji.1830250523pmid: 7774631

The role of major histocompatibility complex (MHC) class I and class II molecules in natural killer (NK) cell‐mediated rejection of allogeneic, semi‐syngeneic and MHC‐matched bone marrow grafts was investigated. The use of β2‐microglobulin (β2m) ‐/‐ and β2m +/‐ mice as bone marrow donors to MHC‐mismatched recipients allowed an analysis of whether the presence of semi‐syngeneic and allogeneic MHC class I gene products would be triggering, protective or neutral, in relation to NK cell‐mediated rejection. Loss of β2m did not allow H‐2b bone marrow cells to escape from NK cell‐mediated rejection in allogeneic (BALB/c) or semi‐allogeneic (H‐2Dd transgenic C57BL/6) mice. On the contrary, it led to stronger rejection, as reflected by the inability of a larger bone marrow cell inoculum to overcome rejection by the H‐2‐mismatched recipients. In H‐2‐matched recipients, loss of β2m in the graft led to a switch from engraftment to rejection. At the recipient level, loss of β2m led to loss of the capability to reject H‐2‐matched β2m‐deficient as well as allogeneic grafts. When MHC class II‐deficient mice were used as donors, the response was the same as that against donors of normal MHC phenotype: allogeneic and semi‐syngeneic grafts were rejected by NK cells, while syngeneic grafts were accepted. These data suggest a model in which allogeneic class I molecules on the target cell offer partial protection, while certain syngeneic class I molecules give full protection from NK cell‐mediated rejection of bone marrow cells. There was no evidence for a role of MHC class II molecules in this system.

Wildner, Gerhild; Thurau, Stephan R.

doi: 10.1002/eji.1830250524pmid: 7774632

Oral administration of retinal soluble antigen (S‐Ag) suppresses the induction of S‐Ag‐mediated experimental autoimmune uveitis (EAU) in Lewis rats. EAU induced with interphotoreceptor retinoid‐binding protein (IRBP), another retinal autoantigen, can also be suppressed by oral administration of IRBP. It has been speculated that feeding with one retinal autoantigen could suppress induction of uveitis with the other retinal protein by means of bystander suppression. Both uveitogenic effector and suppressor cells should find their antigens within the retina, where the suppressor cells would be expected to act on the effector cells. However, reciprocal combinations of antigens used for induction and suppression of uveitis failed to prevent onset of disease, demonstrating that bystander suppression obviously does not occur in the eye. To investigate further the localization of suppressor mechanisms, we fed Lewis rats either with retinal S‐Ag or with ovalbumin (OVA) and then immunized the animals either with a mixture of S‐Ag and OVA or with each antigen separately, injected into contralateral hind legs. Feeding of S‐Ag prior to immunization led to suppression of uveitis, whereas feeding of OVA had no tolerizing effect when S‐Ag and OVA were injected into different legs. Nevertheless, immunizing rats with a mixture of S‐Ag and OVA after OVA feeding suppressed uveitis to a high degree. These findings suggest that orally induced bystander suppression might not occur in the target organ, but rather peripherally at the site of induction of the autoimmune T cells.

Prigione, Ignazia; Facchetti, Paola; Ghiotto, Fabio; Tasso, Paola; Pistoia, Vito

doi: 10.1002/eji.1830250525pmid: 7774633

Human Toxoplasma gondii (Tg)‐specific T cell clones were raised by infecting peripheral blood mononuclear cells (MNC) from two healthy, latently infected individuals with Tg trophozoites. All of the clones had a CD4+ immunophenotype and produced simultaneously interleukin (IL)‐2, interferon (IFN)‐γ, IL‐4 and IL‐5 upon mitogen or antigen stimulation. Tg‐specific T cell clones were classified as T helper of type 0 (ThO) since most of them released roughly comparable amounts of IFN‐γ and IL‐4. In some clones, a trend to an increased production of IFN‐γ following antigen‐specific as compared to non‐specific stimulation was observed. The ThO phenotype was also expressed by T cell clones that had been raised from bulk cultures performed in the presence of IL‐4 or IFN‐γ. All of the Tg‐specific T cell clones were cytolytic in a non‐specific assay which involves the triggering of the CD3‐T cell receptor (TcR) complex. Some clones specifically lysed an autologous lymphoblastoid cell line (LCL) that had been infected with Tg trophozoites. Finally, most of the Tg‐specific T cell clones produced IL‐10, irrespective of whether they had been raised from bulk cultures incubated in the presence or absence of IL‐4 or IFN‐γ. Taken together, these findings suggest that Tg‐specific ThO helper cell clones from healthy, latently infected individuals, beside activating toxoplasmacidal mechanisms through IFN‐γ release, might limit the magnitude of the immune response to the parasite by killing Tg‐infected antigen‐presenting cells and by releasing IL‐10.

Dianzani, Umberto; Bragardo, Manuela; Buonfiglio, Donatella; Redoglia, Valter; Funaro, Ada; Portoles, Pilar; Rojo, José; Malavasi, Fabio; Pileri, Alessandro

doi: 10.1002/eji.1830250526pmid: 7539755

CD4, a lymphocyte surface glycoprotein, serves as co‐receptor for antigen with the T cell receptor (TCR). It is also the lymphocyte receptor for HIV by binding the gp120 viral envelope protein. Interaction of gp120 with CD4 is crucial for viral infection, but is not sufficient to allow viral entry into cells. Recombinant gp120 alters CD4+ T cell responsiveness to activation stimuli. To express its co‐receptor function fully, CD4 must be laterally associated with the TCR and CD45 to form multi‐receptor complexes competent to transduce potent activation signals. Here, we examine the possibility that gp120/CD4 binding alters lateral associations of CD4 with other lymphocyte surface molecules, and that assembly of abnormal multi‐molecular complexes is involved in the gp120‐induced CD4+ T cell dysfunction and in viral entry. In the absence of gp120, CD4 displayed high association with CD3, CD5, CD45RC, CD25, CD28, CD44, and CD53; weak association with CD2, CD38, CD45RB, CD62L, and CD26; and no association with CD45RA, CD45RO, CD11b, CD11a, CD54, CD7, CD48, CD98, CD59, CD55, HLA class I and class II molecules. Treatment with gp120 significantly increased CD4 association with CD3, CD45RA, CD45RB, CD59, CD38, CD26, and HLA class I, and decreased that with CD45RC. Specificity of these results were assessed at various levels. First, gp120 did not influence lateral associations displayed by other molecules, such as HLA class II. Second, the Leu3 mAb, which binds CD4 on a site overlapping the gp120 binding site, did not elicit the same CD4 lateral associations as gp120, and finally, a direct gp120/CD4 interaction was needed to induce the lateral associations, as shown by the observation that blocking the gp120/CD4 binding by the Leu3 mAb inhibited the gp120‐induced associations. These results can be interpreted in several ways. gp120/CD4 interaction could trigger an inside‐out signal responsible for the associations, or gp120 could induce steric modifications of CD4 that increase its affinity for the associating molecules. Alternatively, these molecules may interact directly with gp120, bridging them with CD4. It is also possible that the associations may be mediated by additional components, interacting with both gp120 and the associating surface molecule. The last hypothesis is likely for CD59, whose gp120‐induced association with CD4 required the presence of serum in the co‐capping assay. Since both CD59 and gp120 bind complement, the observed association could be mediated by complement components.

Wallace, Valerie A.; Kawai, Kazuhiro; Levelt, Christiaan N.; Kishihara, Kenji; Molina, Thierry; Timms, Emma; Pircher, Hanspeter; Penninger, Josef; Ohashi, Pamela S.; Eichmann, Klaus; Mak, Tak W.

doi:

Haruna, Hiroki; Inaba, Muneo; Inaba, Kayo; Taketani, Shigeru; Sugiura, Kikuya; Fukuba, Yoh; Doi, Hiroshi; Toki, Junko; Tokunaga, Rikio; Ikehara, Susumu

doi: 10.1002/eji.1830250528pmid: 7539756

The age‐related changes in the function of antigen‐presenting cells (APC) were examined using a substrain of senescence‐accelerated mouse (SAMP1). In the primary mixed lymphocyte reaction (MLR), dendritic cells (DC) from aged SAMP1 mice showed less stimulatory activity than those of age‐matched BALB/c or young SAMP1 mice. In the secondary MLR, the stimulatory activity of B cells was found to be lower in aged SAMP1 mice but not in age‐matched BALB/c or young SAMP1 mice. In addition, these age‐related decreases in the stimulatory activity of APC were found to be related to changes in the surface density of major histocompatibility complex class II and intercellular adhesion molecule‐1 (ICAM‐1) (but not B7‐1 or B7‐2 molecule) on APC (DC and B cells).

Vidović, Damir; Falcioni, Fiorenza; Bolin, David R.; Nagy, Zoltan A.

doi: 10.1002/eji.1830250529pmid: 7774635

The recognition of antigenic peptides by CD4+ helper T cells is demonstrated here to result in a dramatic (up to 90%) decrease in expression of major histocompatibility complex (MHC) class II molecules on the surface of antigen‐presenting cells (APC). The reduction is selective to the class II isotype presenting the antigen, but if affects both allelic forms of the same isotype in heterozygous APC. The observed MHC down‐regulation requires a specific T cell receptor‐peptide‐class II interaction, a direct contact between T cell and APC, and the involvement of CD2 molecules. These findings have important implications for the regulation of immune response, self tolerance, and autoimmunity.

Oka, Yoshihiro; Rolink, Antonius G.; Suematsu, Sachiko; Kishimoto, Tadamitsu; Melchers, Fritz

doi: 10.1002/eji.1830250530pmid: 7774636

Long‐term proliferating, stromal cell/interleukin (IL)‐7‐reactive precursor B cell lines established from fetal liver and bone marrow of human IL‐6‐transgenic B6Ld46 mice produce and secrete human IL‐6. When transplanted into severecombined immunodeficient (SCID) or Rag2 knockout (Rag2‐T) mice, these pre‐B cell lines establish a part of the B cell compartment but yield no T cells, as do pre‐B cell lines from genetically matched non‐transgenic mice. Within 2 to 3 months after transplantation, the serum of mice transplanted with pre‐B cells from normal mice contains normal levels of IgM (200–600 μg/ml) but 10–100‐fold lower levels of the IgG subclasses and of IgA. In contrast, the sera of mice transplanted with IL‐6 transgenic pre‐B cells contain not only IgM, but also IgG and IgA at nearly normal levels. The results indicate that at least a part of the plasmacytosis and elevated IgG production observed previously in the IL‐6‐transgenic mice appears to be due to a T cell‐independent activation of IgG and IgA production by the IL‐6‐secreting pre‐B cells and their differentiated progeny in the immunodeficient hosts.