Interferon suppresses antigen- and mitogen-induced leukocyte migration inhibition

Interferon-gamma inhibits T84 epithelial cell migration by redirecting transcytosis of beta1 integrin from the migrating leading edge

Intestinal inflammation is associated with epithelial damage and formation of mucosal wounds. Epithelial cells migration is required for wound closure. In inflammatory status, migrating epithelial cells are exposed to proinflammatory cytokines such as IFN-gamma. However, influence of such cytokines on intestinal epithelial wound closure remains unknown. The present study was designed to investigate the effect of IFN-gamma on migration of model T84 intestinal epithelial cells and recovery of epithelial wounds. IFN-gamma significantly inhibited rate of T84 cell migration and closure of epithelial wounds. This effect was accompanied by the formation of large aberrant lamellipodia at the leading edge as well as significant decrease in the number of beta(1) integrin containing focal adhesions. IFN-gamma exposure increased endocytosis of beta(1) integrin and shifted its accumulation from early/recycling endosomes at the leading edge to a yet unidentified compartment at the cell base. This redirection in beta(1) integrin transcytosis was inhibited by depolymerization of microtubules with nocodazole and was unaffected by stabilization of microtubules with docetaxel. These results suggest that IFN-gamma attenuates epithelial wound closure by microtubule-dependent redirection of beta(1) integrin transcytosis from the leading edge of migrating cells thereby inhibiting adequate turnover of focal adhesion complexes and cell migration.

Suppression of virus-specific antibody production by CD8+ class I-restricted antiviral cytotoxic T cells in vivo

The question of whether virus-induced immunosuppression includes the antibody response against the infecting virus itself was evaluated in a model situation. Transgenic mice expressing the T-cell receptor (TCR) specific for peptide 32-42 of lymphocytic choriomeningitis virus (LCMV) glycoprotein 1 presented by Db reacted with a strong transgenic cytotoxic T-lymphocyte (CTL) response starting on day 3 after infection with a high dose (10(6) PFU intravenously [i.v.]) of the WE strain of LCMV (LCMV-WE); LCMV-specific antibody production in the spleen was suppressed in these mice. Low-dose (10(2) PFU i.v.) infection resulted in an antiviral antibody response comparable to that of the transgene-negative littermates. The induction of suppression of LCMV-specific antibody responses was specifically mediated by CD8+ TCR transgenic CTLs, since the LCMV-8.7 variant virus (which is not recognized by transgenic TCR-expressing CTLs because of a point mutation) did not induce suppression. In addition, treatment with CD8 monoclonal antibody in vivo abrogated suppression. Once suppression had been established, it was found to be nonspecific. The abrogation of antibody responses depended on the relative kinetics of the antibody response involved and the kinetics of the anti-LCMV CTL response. Analysis of T- and B-cell subpopulations showed no significant changes, but immunohistochemical analysis of spleens revealed extensive destruction of follicular organization in lymphoid tissue by day 4 in transgenic mice infected with LCMV-WE but not in those infected with the CTL escape mutant LCMV-8.7. Impairment of antigen presentation rather than of T or B cells was also suggested by adoptive transfer experiments, showing that transferred infected macrophages may improve the anti-LCMV antibody response in LCMV-immunosuppressed transgenic recipients; also, T and B cells from suppressed transgenic mice did respond in irradiated and virus-infected nontransgenic mice with antibody formation to LCMV. Such virus-triggered, T-cell-mediated immunopathology causing the suppression of B cells and of protective antibody responses, including those against the infecting virus itself, may permit certain viruses to establish persistent infections.

Immunosuppression in mice by lymphocytic choriomeningitis virus infection: time dependence during primary and absence of effects on secondary antibody responses

The kinetic study of immunosuppression caused by infection of mice with lymphocytic choriomeningitis virus WE (LCMV-WE) was assessed in DBA/2 (H-2d) and C57BL/6 (H-2b) mice. Infection with LCMV caused suppression of the Day 4 IgM response (complete in DBA/2 and incomplete in C57BL/6) and completely suppressed IgG responses on Days 9 and 42 to vesicular stomatitis virus (VSV) injected 2-11 days after LCMV. Suppression was partial when VSV was injected 16-28 days after LCMV-WE infection. The observed suppression between Day 2 and Day 11 was complete and nonspecific as revealed by the fact that these mice could not mount a secondary response to VSV when reinjected with the same VSV 42 days later. Nonspecificity of suppression was further indicated by the finding that the kinetics of recovery from suppression of the anti-VSV response were comparable for the VSV serotype used during the 2- to 11-day period after LCMV infection as for the serologically noncross-reactive second VSV serotype; both anti-VSV responses had recovered by Days 56-82 after LCMV infection. Once an anti-VSV antibody response was established, a subsequent LCMV-WE infection had no suppressive effect on Day 2 or Day 42 after a primary VSV infection. Also, the capacity of VSV-primed mice that were LCMV infected to respond to VSV in a secondary challenge infection with the same VSV was not impaired.

Effects of interferons-alpha, -beta, and -gamma on human interleukin-2 production

Interleukin-2 (IL-2) production was stimulated with staphylococcus enterotoxin A, heat-killed Staphylococcus aureus, or concanavalin A (ConA) in cultures of human peripheral blood mononuclear cells (PBMC). IL-2 was characterized by its effect on IL-2-dependent cytotoxic T lymphocytes (CTLL cells) and mouse thymocytes. Pretreatment of PBMC with greater than or equal to 100 IU/ml of human-alpha (HuIFN-alpha) or interferon-beta (HuIFN-beta), or with greater than or equal to 10 IU/ml HuIFN-gamma for 4 h enhanced the IL-2 production. The effects of 20-h IFN treatments were less pronounced or they exerted an inhibitory effect. Our results indicate that IFNs modulate IL-2 production, which in turn can mediate some of the immunomodulatory effects of IFNs.

Modulation of granulocyte oxidative response by recombinant interferon alpha 2 and gamma

Interferon (IFN) has been described to influence various cellular functions. In this study we investigated whether the oxidative response of polymorphonuclear leukocytes (PMN) is also affected by IFN. In order to exclude the possible influence of impurities in IFN preparations, only recombinant human IFN alpha 2 or gamma were used. Lucigenin-dependent chemiluminescence (CL) of PMN was measured to assess the production of oxygen radicals. IFN gamma at a concentration of more than 10 ng/ml elicited a minimal CL response in PMN. When PMN were incubated with IFN gamma for 1 h and then stimulated with chemotactic peptide f-met-phe (FMP), zymosan-activated serum (ZAS), zymosan particles, or phorbol-myristate acetate (PMA), the CL response was increased as consequence of the generally enhanced oxidative metabolism. IFN alpha 2 showed no such effect at any concentration tested. A 5-min pretreatment with IFN gamma decreased the ZAS response but did not affect the reaction to the other stimuli. The possibility of a generation of IFN by PMN during the assay could be excluded as no IFN activity could be detected in an antiviral assay after stimulation of PMN for 6 h with PolyI X PolyC, LPS, ConA, C. parvum, PMA, zymosan, or FMP. The modulation of granulocyte activity by IFN gamma may be important in the regulation of the anti-inflammatory response of PMN.

Absence of interferons-alpha and -gamma in renal lesions of systemic lupus erythematosus and membranous glomerulonephritis

Frozen kidney biopsy sections from nine patients with systemic lupus erythematosus (SLE) as well as many other renal diseases, including IgA nephropathy, membranous nephritis, and minimal change nephrotic syndrome, were negative for interferons -alpha and -gamma by immunofluorescence. Lupus patients studied included several subjects with marked serum elevations of interferon activity as well as others with low or negative serum interferon levels. Isolated glomerular eluates prepared from normal and SLE kidneys showed no functional interferon activity by virus plaque inhibition assay. Components of normal as well as SLE serum showed no direct binding to interferon -alpha or -gamma by ELISA assays.

Interferon amplifies complement activation by Burkitt's lymphoma cells

Interferon was originally described as an antiviral agent produced shortly after onset of infection with most viruses. However, in addition to inducing an antiviral state, interferon inhibits cell division, increases the expression of cell-surface antigens, boosts the cytotoxic activity of natural killer (NK) cells and modulates several immune functions of lymphocytes and macrophages. Moreover, a special class of interferon (immune interferon or IFN-gamma) is produced by T cells following stimulation with antigen or interaction with mitogens. The different methods by which interferon is induced and its multiple effects suggest that it may be part of a first-line defence system controlling the spread of virus infections and the proliferation of modified 'self' cells that have been affected by virus infection or neoplastic transformation. The ability of certain human lymphoma cells to activate the alternative pathway of complement is well established. Here we show that monoclonal antibody-purified interferon can amplify the ability of certain tumour cells to activate complement via the alternative pathway. This demonstration may reflect an additional, as yet unknown, role of interferon in inducing non-specific anti-tumour immunity.

In vitro migration inhibition of [3H]leucine-labeled granulocytes by supernatants of Con A-Sepharose stimulated MNC cultures

By measuring in vitro migration of [3H]leucine-labeled granulocytes from agarose containing capillary tube fragments, the migration inhibitory activity of supernatants of Con A-Sepharose stimulated MNC cultures was tested. The sensitivity of the method was increased by using higher dilutions of granulocytes in agarose (from 10(7)/1 microliter to 10(7)/3-4 microliter). Serum-free assays have been used for characterizing the migration inhibitory activity in this system. The migration inhibitory activity was abolished by absorption on granulocytes or by heating (56 degrees C, 80 degrees C). Other factors such as L-fucose, N-acetyl-D-glucosamine, DFP or BAEE showed only moderate or insignificant impairing effects on migration inhibitory activity of crude supernatants of Con A-Sepharose stimulated MNC cultures.

Differential cytostatic effect of interferon on murine BALB/c B- and T-cell tumors

The cytostatic effect of murine interferon (IFN) on several BALB/c-derived B- and T-cell tumor cells was examined. After incubation for 1 h in vitro with 1000 U of IFN, followed by intraperitoneal inoculation, tumor formation was not decreased in the case of B cell tumors or Lyt-1+2- or Lyt-1+2+3+ T cells tumors. Under the same conditions, the onset of tumor formation for Lyt-2+3+ T-cell tumors was delayed and the final incidence decreased. When the effect of IFN on cell multiplication in vitro was examined, Lyt-2+3+ T-tumor cells were found to be more sensitive to the cytostatic effect of IFN than Lyt-1+2+3+ T-tumor cells. This shows that the sensitivity of lymphocyte-derived tumor cells to the cytostatic effect of IFN is influenced by the type of differentiation of the cells.

Interferon activates macrophages to produce plasminogen activator

Macrophages and monocytes become activated, by a variety of mechanisms, to exhibit cytotoxicity. Associated with this activation for cytotoxicity is the production of certain neutral proteases, especially plasminogen activator (PA), which may be involved in the mechanism of cytolysis. Supernatants from concanavalin A (Con A) or antigen-stimulated spleen cells contain factor(s) which render macrophages and monocytes activated in vitro (MAF/MIF). We have found that in addition to such spleen cell supernatants murine interferon was able to activate peptone-induced C57BL/6 peritoneal macrophages to produce PA but had no effect on human monocytes. Similarly, human recombinant interferon activated human monocytes but not murine macrophages to produce PA. In addition to displaying this species specificity, interferon was able to function as a monocyte/macrophage activator in this system just as in cytotoxicity and may be a regulator of monocyte/macrophage function in vivo by modulation of proteolytic enzymes.