Interleukin-6 is a mediator of TNF-alpha regulation of LAK cell function

Tumor necrosis factor increases interleukin-6 release from adrenal zona glomerulosa cellsin vitro

Rat adrenal zone glomerulosa cells secrete tumor necrosis factor (TNF) and interleukin-6 (IL-6). We have extended previous studies to determine if TNFα can modify the release of adrenal IL-6. Primary cultures of rat adrenal zone glomerulosa cells were prepared by enzymatic techniques and cultured for 4-6 days. The cells were then exposed to serum-free RPMI 1640 incubation medium containing vehicle (RPMI-1640 medium alone), TNFα and/or selected agents known to stimulate adrenal IL-6 release. Following a 5 h incubation, the incubation medium was removed from the cells and the IL-6 content of the medium measured with the 7TD1 bioassay. TNFα (0.5-50 ng/mL) increased basal adrenal IL-6 release in a concentration-dependent manner. Furthermore, TNFα potentiated in a more than additive manner the adrenal IL-6 release stimulated by lipopolysac-charide (LPS), interleukin-1β, angiotensin II and ACTH. TNFα potentiated the IL-6 release stimulated by a wide range of concentration of IL-lβ (0.01-100 ng/mL) and ACTH (0.1-100 nM). Because IL-6 and TNFα modify the steroid secretion from adrenal cells, these cytokines may interact together to regulate the function of the adrenal cortex.

Human recombinant IL-4 decreases the emergence of non-specific cytolytic cells and favours the appearance of memory cells (CD4+CD45RO+) in the IL-2-driven development of cytotoxic T lymphocytes against autologous ovarian tumour cells

As IL-4 and IL-6 have also been reported to promote the development of T lymphocytes such as IL-2, we investigated their role in the development of specific cytotoxic T lymphocytes (CTL) against autologous ovarian tumours in mixed lymphocyte tumour cultures (MLTC). Peripheral blood lymphocytes (PBL) from five ovarian carcinoma (OC) patients were incubated with autologous OC cells at a PBL:OC cell ratio of 20:1 in IL-2 alone (50 U/ml for the first week and 200 U/ml thereafter) or with IL-4 (100 U/ml) and/or IL-6 (5 U/ml). Neither IL-4 nor IL-6 improved lymphocyte proliferation consistently. In contrast, IL-4 reduced significantly the development of LAK activity as assayed against Daudi cell line, and decreased modestly the emergence of natural killer (NK) activity as assayed against K562. This property was not shared by IL-6. The prevention of the development of non-specific cytolytic activity (LAK and NK activities) was much stronger when the MLTC was started with IL-4 in the absence of IL-2 during the first week in culture. A concomitant drop in NKH-1 expression (CD56) was observed. By inhibiting the emergence of non-specific cytotoxicity, IL-4 provided better evidence of the specific cytolytic activity directed at ovarian cells. In parallel, a significant increase in the generation of memory cells (CD4+CD45RO+) was observed with IL-4. In conclusion, in this model, IL-4 added before IL-2 decreases significantly the emergence of non-specific cytotoxic cells, and promotes the generation of memory cells. These properties may be of interest in the design of strategies aimed at obtaining tumour-specific cells for investigational and immunotherapeutic purposes.

Immunomodulation in patients receiving intravenous Bryostatin 1 in a phase I clinical study: comparison with effects of Bryostatin 1 on lymphocyte function in vitro

Bryostatin 1 is a protein kinase C activator that inhibits growth of tumour cells and activates lymphocytes in vitro, properties that have encouraged its use in phase 1 clinical studies as an anticancer agent. We investigated interleukin-2(IL-2)-induced proliferation and lymphokine-activated killer (LAK) cell activity in peripheral blood mononuclear cells (PBMC) from cancer patients receiving Bryostatin intravenously. After Bryostatin administration both LAK generation and proliferation were enhanced when patients' PBMC were stimulated with IL-2 in vitro. However, when normal donors' PBMC were cultured in vitro in the presence Bryostatin and IL-2, LAK induction was inhibited while IL-2-driven proliferation was increased. These effects were also seen following only 2 h exposure to Bryostatin and could be elicited by conditioned medium from Bryostatin-pretreated cells. Neither IL-4 nor interferon gamma was detected in the conditioned medium. Bryostatin in vitro was found to increase expression of IL-2 receptors on CD4+, CD8+ and CD56+ cells and augment the proportion of CD8+ cells in conjunction with IL-2. We conclude that Bryostatin in combination with IL-2 in vitro enhances proliferation and IL-2 receptor expression on lymphocytes, favouring CD8+ cells while suppressing the generation of LAK activity. Intravenous administration of Bryostatin increases the potential of IL-2 to induce proliferation and LAK activity in lymphocytes which, taken together with its putative direct antitumour effect, makes Bryostatin an interesting candidate for clinical trials in combination with IL-2.