Coexpression of two distinct genes is required to generate secreted bioactive cytotoxic lymphocyte maturation factor.

Abstract

Cytotoxic lymphocyte maturation factor (CLMF) is a disulfide-bonded heterodimeric lymphokine that (i) acts as a growth factor for activated T cells independent of interleukin 2 and (ii) synergizes with suboptimal concentrations of interleukin 2 to induce lymphokine-activated killer cells. We now report the cloning and expression of both human CLMF subunit cDNAs from a lymphoblastoid B-cell line, NC-37. The two subunits represent two distinct and unrelated gene products whose mRNAs are coordinately induced upon activation of NC-37 cells. Coexpression of the two subunit cDNAs in COS cells is necessary for the secretion of biologically active CLMF; COS cells transfected with either subunit cDNA alone do not secrete bioactive CLMF. Recombinant CLMF expressed in mammalian cells displays biologic activities essentially identical to natural CLMF, and its activities can be neutralized by monoclonal antibodies prepared against natural CLMF. Since this heterodimeric protein displays the properties of an interleukin, we propose that CLMF be given the designation interleukin 12.The molecular cloning and expression of recombinant cytokines has made possible both significant advances in our understanding of the molecular basis of immune responses and the development of new approaches to the treatment of disease states. As an example, recombinant interleukin 2 (recombinant IL-2) has been shown to be capable of causing regression of established tumors in both experimental animals (1) and in man (2); however, its clinical use has been associated with significant toxicity (2). One potential approach to improving the therapeutic utility of recombinant cytokines is to use them in combination (3,4 MATERIALS AND METHODScDNA Cloning. A subline of NC-37 cells selected for its ability to produce high levels of CLMF (7), NC-37.98, was induced with phorbol 12-myristate 13-acetate (PMA) and calcium ionophore A23187 for 16 hr. Poly(A)+ RNA was isolated, and random hexamer-primed cDNA libraries were established in phage AgtlO by standard procedures. Mixedprimer polymerase chain reaction (PCR) using controlled ramp times (8) was performed as follows. PCR primers contained all possible codons and were 14 or 15 nucleotides long ( Fig. 1) with a 5' extension of 9 nucleotides containing an EcoRI site for subcloning. Degeneracies varied from 1 in 32 to 1 in 4096; 0.5-4 pmol per permutation of forward and reverse primer was used in a 50-to 100-,lI PCR mixture with 40 ng of cDNA made from NC-37.98 cells that had been activated by culture with 10 ng of PMA and 25 ng of calcium ionophore A23187 per ml for 16 hr (40-kDa subunit) or with 3 ,tg of human genomic DNA (35-kDa subunit). PCR cycling parameters were as follows. Initial denaturation was at 95°C for 7 min. Low-stringency annealing was performed by cooling to 37°C over 2 min, incubating 2 min at 37°C, heating to 72°C over 2.5 min, extending at 72°C for 1.5 min, heating to 95°C over 1 min, and denaturing at 95°C for 1 min. This cycle was repeated once. Thirty standard cycles (40-kDa subun...

New insights into IL-12-mediated tumor suppression

“…7,8 IL-12 is a heterodimer with a molecular weight of 70 kDa consisting of a heavy (p40) and a light (p35) chain subunit, which are covalently linked by disulfide bonds. [9][10][11] While p40 is produced in abundance by phagocytic cells, p35 is ubiquitously and constitutively expressed only at low levels and is thought to require p40 co-expression for secretion of the biologically active cytokine. 12 The sensing of IL-12 is mediated through the heterodimeric IL-12 receptor (IL-12R) composed of IL-12Rb1 and IL-12Rb2.…”

CD40L‐expressing CD8 T cells prime CD8α+ DC for IL‐12p70 production

“…DC responded to freshly isolated CD8 T cells during a peptide-specific interaction by producing IL-12p40, similarly to LPS (Fig. 2A); however, no IL-12p70, the heterodimeric cytokine comprising of p35 and p40 subunits responsible for Th1-inducing ability [16,22,23], was detected under these conditions (Fig. 2B).…”

In case of obesity, longevity-related mechanisms lead to anti-inflammation

“…The genes encoding p35 and p40 are located on separate chromosomes (Wolf et al 1991;Sieburth et al 1992;Schoenhaut et al 1992) and therefore their expression is independently regulated. Co-expression of both subunits is required to form the biologically active, secreted p70 heterodimer (Gubler et al 1991). IL-12 p40 is produced in much greater quantities than is required to form heterodimers (Wysocka et al 1995).…”