A cDNA coding for human interleukin-2 (IL-2) has been cloned from a cDNA library prepared from partially purified IL-2 mRNA. The DNA sequence codes for a polypeptide which consists of 153 amino acids including a putative signal sequence. A biologically active polypeptide, characteristic of human IL-2, was produced when the cDNA was fused to a simian virus 40 promoter sequence and used to transfect cultured monkey COS cells.

Structure and expression of a cloned cDNA for human interleukin-2

Cyclosporin A blocked production of the lymphokine interleukin 2 by activated T lymphocytes. In a human and a murine cell line this inhibition reflected an absence of interleukin 2 messenger RNA. Under conditions in which these cells are normally stimulated to secrete high levels of interleukin 2, they failed to do so in the presence of cyclosporin A. In both cell lines this failure was accompanied by an absence of interleukin 2 messenger accumulation.

Induction of interleukin 2 messenger RNA inhibited by cyclosporin A.

Xenogeneic monoclonal antibodies were prepared to the murine interleukin 2 (IL-2)-dependent HT2 cell line. One rat IgM monoclonal antibody (7D4) was identified that inhibited proliferation of the HT2 cells and of IL-2-dependent CTLL cells in the presence of crude rat IL-2 as well as of purified human IL-2. The level of inhibition was dependent on both antibody and IL-2 concentration. Cell distribution studies using a fluorescence-activated cell sorter showed that the antigen identified by 7D4 is expressed at a high density on HT2 cells and on concanavalin A (Con A)-induced T-cell blasts and at a substantially lower density on lipopolysaccharide-induced B-cell blasts; 7D4 binding was not detected on greater than 95% of nonactivated thymocytes, T cells, or B cells. Competition binding studies indicated that 7D4 fails to inhibit the binding of 3H-labeled human IL-2 to CTLL cells. However, 7D4 specifically immunoprecipitated 3H-labeled human IL-2 from detergent extracts of HT2 cells or Con A-induced T-cell blasts that had been pulsed with [3H]IL-2; in contrast, 7D4 did not react with free [3H]IL-2. Initial biochemical analysis of immunoprecipitates with 7D4 of detergent extracts from surface-iodinated Con A-activated spleen cells showed a major band having apparent molecular weight of 48,000-62,000. Collectively, these results suggest that 7D4 detects an epitope on the IL-2 receptor distal to the ligand binding site or another molecule that physically associates with the receptor.

https://www.pnas.org/content/pnas/80/18/5694.full.pdf

Identification and initial characterization of a rat monoclonal antibody reactive with the murine interleukin 2 receptor-ligand complex

Spleen cells from C57BL/6 mice immunized in vivo with a syngeneic Friend virus-induced leukemia, FBL-3, were specifically activated by culture for 7 d with FBL-3, then nonspecifically induced to proliferate in vitro for 12 d by addition of supernatants from concanavalin A-stimulated lymphocytes containing interleukin 2 (IL-2). Such long-term cultured T lymphocytes have previously been shown to specifically lyse FBL-3 and to mediate specific adoptive therapy of advanced disseminated FBL-3 when used as an adjunct to cyclophosphamide (CY) in adoptive chemoimmunotherapy. Because the cultured cells are dependent upon IL-2 for proliferation and survival in vitro, their efficacy in vivo is potentially limited by the availability of endogenous IL-2. Thus, the aim of the current study was to determine whether exogenously administered purified IL-2 could augment the in vivo efficacy of long-term cultured T lymphocytes. Purified IL-2 alone or as an adjunct to CY as ineffective in tumor therapy. However, IL-2 was extremely effective in augmenting the efficacy of IL-2-dependent long-term cultured T lymphocytes in adoptive chemoimmunotherapy. The mechanism by which IL-2 functions in vivo is presumably by promoting in vivo growth and/or survival of adoptively transferred cells. This assumption was supported by the findings that IL-2 did not enhance the modest therapeutic efficacy of irradiated long-term cultured cells that were incapable of proliferating in the host and was ineffective in augmenting the in vivo efficacy of noncultured immune cells that are not immediately dependent upon exogenous IL-2 for survival.

https://rupress.org/jem/article-pdf/155/4/968/1393726/968.pdf

Augmentation of the anti-tumor therapeutic efficacy of long-term cultured T lymphocytes by in vivo administration of purified interleukin 2.

Interleukin-12 (IL-12) is a potent immunoregulatory cytokine that is crucially involved in a wide range of infectious diseases. In several experimental models of bacterial, parasitic, viral, and fungal infection, endogenous IL-12 is required for early control of infection and for generation and perhaps maintenance of acquired protective immunity, directed by T helper type 1 (Th1) cells and mediated by phagocytes. Although the relative roles of IL-12 and gamma interferon in Th1-cell priming may be to a significant extent pathogen dependent, common to most infections is that IL-12 regulates the magnitude of the gamma interferon response at the initiation of infection, thus potentiating natural resistance, favoring Th1-cell development; and inhibiting Th2 responses. Treatment of animals with IL-12, either alone or as a vaccine adjuvant, has been shown to prevent disease by many of the same infectious agents, by stimulating innate resistance or promoting specific reactivity. Although IL-12 may enhance protective memory responses in vaccination or in combination with antimicrobial chemotherapy, it is yet unclear whether exogenous IL-12 can alter established responses in humans. Continued investigation into the possible application of IL-12 therapy to human infections is warranted by the role of the cytokine in inflammation, immunopathology, and autoimmunity.

https://cmr.asm.org/content/cmr/10/4/611.full.pdf

Interleukin-12 in infectious diseases.

The isolation of specific T cell growth factors termed interleukin 2 (IL 2) is changing the approach to understanding T cell function. This class of growth factors has allowed te establishment of a number of human and murine T cell lines. We summarize the biochemical properties of human and murine IL 2. Studies have been initiated to isolate mRNA encoding for IL 2. Such RNA can be translated in rabbit reticulocyte lysates yielding IL. 2. This RNA may be useful for the development of probes to isolate lymphokine genes.

Carol A. Ramthun

Papers

Molecular Characterization of Interleukin 2