Qualitative differences in effects of recombinant alpha-, beta- and gamma-interferons on human peripheral blood leukocytes in vitro

2',5'-Oligoadenylate synthetase levels in patients with multiple myeloma receiving maintenance therapy with interferon alpha 2b do not correlate with clinical response

In clinical trials with interferon alpha 2b (IFN-alpha 2b) as maintenance therapy for multiple myeloma, the therapeutic benefit is inconclusive. Although the mechanism(s) by which IFN-alpha 2b prolongs remission in some patients is unknown, 2',5'-oligoadenylate synthetase (2,5-A synthetase) has been used as an objective indicator that IFN-alpha 2b is active in vivo. The enzyme was assayed in cytosol preparations of peripheral blood mononuclear cells (MNCs) from 111 patients who were receiving IFN-alpha 2b and 54 patients who were not, using an assay which measures the conversion of [alpha-32P]ATP to triphospho(adenylyl 2',5')adenosine. 2,5-A synthetase activity was compared with response to intensive therapy and with duration of maintenance therapy. Seventy-three per cent of patients had measurable amounts of 2,5-A synthetase during the first 6 months of maintenance therapy. This percentage decreased with longer follow-up but not significantly. There was no difference between the magnitude of enzyme induction amongst patients who were in complete remission, partial response or who had no change in disease status following intensive therapy. Peripheral blood T cells were a major source of 2,5-A synthetase activity in patients receiving the cytokine. However, both T and B cells produced the enzyme following exposure to IFN-alpha in vitro. The data show that the level of 2,5-A synthetase in patients with multiple myeloma is not indicative of clinical response to IFN-alpha 2b.

Coexpression of intercellular adhesion molecule-1 and class I major histocompatibility complex antigens on hepatocyte membrane in chronic viral hepatitis

AIMS

To evaluate the role of hepatocyte expression of leucocyte adhesion molecules and major histocompatibility complex (MHC) antigens in the pathogenesis of chronic viral hepatitis.

METHODS

The expression of intercellular adhesion molecule 1 (ICAM-1), lymphocyte function associated antigen 3 (LFA-3), and MHC class I and II antigens on hepatocyte membrane in relation to the histological and biochemical activities was studied in patients with chronic B hepatitis, chronic persistent hepatitis (CPH) n = 23; chronic active hepatitis (CAH) n = 20; chronic D hepatitis (CAH) n = 6; and chronic non-A, non-B hepatitis (CPH n = 4, CAM n = 6). Six of the latter were hepatitis C virus antibody positive.

RESULTS

In chronic B hepatitis ICAM-1 and MHC-I were expressed significantly more in patients with CAH than in those with CPH (p < 0.001), while the expression of LFA-3 and MHC-II showed no significant difference, irrespective of serum HBeAg or hepatitis B virus DNA. Similar findings were noted in non-A, non-B hepatitis. Regardless of the viral aetiology, patients with CAH had a significantly higher degree of ICAM-1 and MHC-I expression than LFA-3 (p < 0.001 v ICAM-1 and MHC-I, respectively) and MHC-II (p < 0.001 v ICAM-1 and MHC-I, respectively) expression. Those with CPH showed little or no difference in the expression of these four molecules. Furthermore, serum ALT values positively correlated with the hepatocyte expression of ICAM-1 (p < 0.001) and MHC-I (p < 0.001), but not LFA-3 (p > 0.05) and MHC-II (p > 0.05).

CONCLUSIONS

In chronic viral hepatitis hepatocyte expression of ICAM-1 and MHC-I might be important for immunosurveillance against virally infected hepatocytes, while the expression of LFA-3 and MHC-II does not seem to have a role in the pathogenesis of chronic viral hepatitis.

Interferon stimulates the expression of 2',5'-oligoadenylate synthetase and MHC class I antigens in insulin-producing cells

The pathogenesis of type 1 diabetes involves autoimmune processes directed against the pancreatic beta-cells. The etiology is not known, but circumstantial evidence suggests a connection between virus infection and development of the disease. Therefore, because the interferon-(IFN) dependent 2',5'-oligoadenylate (2-5A) synthetase system constitutes an important part of the nonspecific immune defense against viral infections, the activity of the enzyme was examined in islets of Langerhans, RIN cells, and GH3 cells. First, the 2-5A synthetase was expressed constitutively in all cell types and, second, all cells were sensitive to stimulation with IFN-alpha. The 2-5A synthetase activity induced by 1,000 U/ml of IFN-alpha increased by 400% in pancreatic islets and by more than 1000% in GH3 and RIN cells. However, the IFN-alpha concentration needed to induce half-maximal 2-5A synthetase activity was nearly the same in the three cell types (i.e., ranging from 59 to 66 U/ml IFN-alpha). The 2-5A synthetase present in islets and RIN cells was highly sensitive to poly (I:C). In pancreatic islets and RIN cells, the 2-5A synthetase enzyme generated dimers and trimers of 2',5'-oligoadenylates. Furthermore, exposure of RIN cells to IFN-alpha showed an increase in MHC class I expression already at 5 U/ml and maximal expression at about 200 U/ml IFN-alpha. The examined endocrine cells express the 2-5A synthetase enzyme as well as MHC class I antigen constitutively, but also by stimulation with IFN in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Alpha interferon therapy for haematological malignancies: correlation between in vivo induction of the 2',5'oligoadenylate system and clinical response

2',5'oligoadenylate (2-5A) synthetase mRNA and enzyme levels have been studied in peripheral blood mononuclear cells from 12 patients with chronic granulocytic leukaemia (CGL), 14 with essential thrombocythaemia (ET) and nine with chronic lymphocytic leukaemia (CLL), undergoing therapy with alpha interferon (alpha IFN). 2-5A synthetase mRNA was assayed by hybridization using the dot-blot technique and the enzyme activity was measured biochemically. A statistically significant difference was observed (P less than 0.05) between the degree of in vivo induction of mRNA by IFN alpha in the total patients between the good and intermediate responders and the poor responders. There was a similar pattern in each of the CGL, ET and CLL groups although this only reached statistical significance in the CGL group. In vitro induction of either mRNA or of enzyme activity, however, did not show a difference between the responders and poor responders in any of the patient groups. Our findings are consistent with the concept that 2-5A has an important role in the anti-tumour activity of alpha IFN and suggest that measurement of in vivo induction of 2-5A synthetase mRNA may be useful in predicting clinical response. In vitro studies, on the other hand, do not provide a reliable predictor of clinical response.

Interferon-gamma (IFN-gamma) and interleukin-2 in the generation of lymphokine-activated killer cell cytotoxicity--IFN-gamma-induced suppressive activity

Incubation of human lymphocytes with recombinant interleukin-2 (rIL-2) results in the generation of lymphokine-activated killer (LAK) cells capable of lysing a wide variety of tumor cells. The present study was undertaken to examine the effect of recombinant gamma interferon (rIFN-gamma) on LAK cell cytotoxicity generated from different peripheral blood mononuclear cell (PBMC) subpopulations. When unseparated PBMC were stimulated by rIL-2 and rIFN-gamma, the latter induced a transient enhancement after 2 days followed by a suppression of LAK cell cytotoxicity at day 6. Enhancement of LAK cell cytotoxicity was moderate and inconstant, whereas the inhibition was strong and observed with all the donors tested. This suppression was not associated with a decrease in the [3H]thymidine uptake. PBMC depleted of adherent cells were more sensitive to the stimulation by rIL-2 and the induced cytotoxicity was not modified by rIFN-gamma. Monocyte-enriched plastic-adherent cells, when incubated with rIL-2 and rIFN-gamma, became cytotoxic after 2-3 days of culture and inhibited LAK cell activity after 5-6 days. Collectively, our results suggest that rIFN-gamma affects LAK cell cytotoxicity through the activation of plastic-adherent, monocyte-rich, cells which modulate natural killer cells, first in a positive, then in a negative way.

Modulation of some Peyer's patch leukocyte functions following in vitro exposure to recombinant bovine alpha- and gamma-interferon

The immunomodulatory effects of recombinant bovine interferon-alpha 1(1) (rBoIFN-alpha 1(1] and -gamma (rBoIFN-gamma) on the response of bovine Peyer's patch leukocytes (PPL) to in vitro mitogenic stimulation were studied. The proliferative response of PPL to concanavalin A (Con A) and pokeweed mitogen (PWM) was significantly inhibited by the addition of 5-1000 units/ml of rBoIFN-alpha 1(1). In contrast, rBoIFN-gamma showed significant enhancement of 3H-Thymidine (3HTdR) incorporation of PPL cultures at concentrations of 5-500 units/ml. Although the results of this study substantiated the previously reported suppressive ability of IFN-alpha 1(1) and the stimulating capacity of IFN-gamma, suppression or enhancement of lymphocyte proliferation was shown to be dependent on the concentration of the polyclonal activator and the length of time the target cells were exposed to IFN. Pre-exposure of target cells to rBoIFN-alpha 1(1) significantly increased its suppressive activity against the PPL response to Con A stimulation. In contrast, pre-exposure of PPL to rBoIFN-gamma did not affect its stimulatory capacity. Prestimulation of target cells with Con A significantly decreased the stimulatory capacity of rBoIFN-gamma and the suppressive activity of rBoIFN-alpha 1(1). These data demonstrate qualitative differences in the effects of rBoIFN-alpha 1(1) compared to those of rBoIFN-gamma on immune cells other than commonly studied circulating leukocytes.

Alteration of beta-2-microglobulin level in malignant lymphoproliferative diseases after a high dose of alpha-2-recombinant interferon

A group of 10 patients with malignant lymphoproliferative diseases resistant to any standard therapeutical modalities were treated with a high dose of alpha-2-recombinant interferon (alpha-2-rIF). Alpha-2-rIF was administered at a total dose of 120 x 10(6) IU in a continuous infusion during 48 h. Two cycles of alpha-2-rIF immunotherapy were employed with an interval of 1 month in between each. Serum and urinary beta-2-microglobulin (B2M) were examined prior to alpha-2-rIF application and on days 2, 4, 6 afterwards. Alpha-2-rIF treatment induced an increase in serum B2M as noted on day 2 followed by a decline to below the normal range. The initial increased value was significantly higher as compared to either the pretreatment value or the normal physiological range. The reduced B2M serum level was protracted and lasted until the second cycle of treatment. Similar but not so great changes in B2M serum values were noted during the second application of alpha-2-rIF. The changes of B2M level in the urine, although less convincing, mimic those observed in the serum. The present results confirmed the biological activity of alpha-2-rIF in malignant lymphoproliferative diseases.

Effects of recombinant bovine interferons-alpha and -gamma on some in vitro immune functions of bovine intraepithelial and lamina propria leukocytes

The effects of recombinant bacteria-derived bovine interferon-alpha I1 (rBoIFN-alpha I1) and -gamma (rBoIFN-gamma) on some in vitro immune functions of bovine intestinal leukocytes were studied. The proliferative response of intraepithelial leukocytes (IEL) to concanavalin A (Con A) was significantly inhibited by the addition of 5-1,000 U/ml of either IFN type. In contrast, addition of rBoIFN-alpha I1 to lamina propria leukocytes (LPL) from the same animal, showed significant inhibition only above 500 U/ml, whereas rBoIFN-gamma revealed significant enhancement when added as low as 50 U/ml. The concentration of mitogen and the time of incubation were both critical factors in determining the outcome of IFN-leukocyte interactions. While both IFN types could inhibit DNA synthesis of both leukocyte cultures at suboptimal (0.5 microgram/ml) Con A concentration throughout the time of incubation, their modulatory activities varied significantly at optimal (5.0 micrograms/ml) and supraoptimal (50.0 micrograms/ml) Con A concentrations. Preexposure of cells to IFNs or prestimulation with Con A did not significantly change the kinetics of IFNs with both leukocyte cultures. Pretreatment of leukocyte cultures with either IFN type for 18 h significantly enhanced the expression of MHC surface antigens. These data demonstrate that purified IFNs produced by recombinant DNA technology can significantly alter some in vitro immune functions of cells other than circulating leukocytes and that different IFNs have different capabilities to alter leukocyte functions.

Action of interferon-alpha on hairy cell leukemia: expression of specific receptors and (2'-5')oligo (A) synthetase in tumor cells from sensitive and resistant patients

IFN-alpha induces tumor regression with a high percentage of complete remissions in hairy cell leukemia. We have recently reported that hairy cells express specific IFN-alpha receptors which are down-regulated upon therapy. We show here that the activity of 2-5 A synthetase, an IFN-induced enzyme, is 2 to 7-fold stimulated in hairy cells from responsive patients within 12-24 h after the first IFN dose. This in-vivo enzyme induction paralleled the kinetics of receptor down-regulation. In one patient who was unresponsive to IFN-alpha treatment neither expression of IFN-alpha receptor nor change in 2-5 A synthetase were expressed and modulated as in sensitive patients. In-vitro treatment of hairy cells with recombinant interferons showed that IFN-beta 1 was able to induce this enzyme to the same extent than IFN-alpha 2, whereas IFN-gamma was inactive despite the presence of specific IFN-gamma receptors. Our results indicate that IFN-alpha can exert its therapeutic effects by acting directly on the hairy cells through interaction with surface membrane receptors. Induction of 2-5 A synthetase can be one of the steps involved in this action. However, both mechanisms, as well as receptor down-regulation are not sufficient to explain the responsiveness of hairy cell leukemia to IFN-alpha.