Induction of interferon-gamma in mouse spleen cells by OK-432, a preparation of Streptococcus pyogenes

A bacterial antitumor and immunopotentiating agent, OK-432, induced Interferon in the spleen cell cultures but not in the thymus cell cultures of various inbred strains of mice. When 1 × 10⁷ spleen cells were cultured in the presence of 5 μg/ml of OK-432, interferon activity was detected as early as 4 hr later and reached a maximum level of about 160 to 500 units/ ml 24 hr later. OK-432-induced interferon was mainly an IFN-γ of molecular weight approximately 40,000, but also contained IFN-α and IFN-β.     

Mechanism of defective NK cell activity in patients with acquired immunodeficiency syndrome (AIDS) and AIDS-related complex. I. Defective trigger on NK cells for NKCF production by target cells, and partial restoration by IL 2

Peripheral blood from patients with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC) exhibits poor NK activity in the 51Cr-release assay. The present studies were undertaken to investigate the mechanism underlying the observed defective NK cytotoxic activity. On the basis of our studies on the mechanism of natural killer cell-mediated cytotoxicity (NKCMC), a defective NK cell can result from lack or decreased frequency of effector cells, inability to recognize and bind the target cell, failure to be activated for the release of NK cytotoxic factors (NKCF), and/or failure to synthesize or secrete NKCF. Each of these various possibilities was examined. Single cell analysis revealed that the frequency of NK cells was comparable to controls, and although the NK cells bind to the NK-sensitive target, the bound target is not lysed. These results suggested that the defect in NK cells was not due to depletion of NK cells or to a defect in recognition structures, but that it was located at the postrecognition event. We previously demonstrated that after binding to target, the NK cell is stimulated to release NKCF in the supernatants and NKCF lyse specifically NK-sensitive targets. Accordingly, we investigated the activation of NK cells from AIDS and ARC patients for release of NKCF. After coculture with the stimulator cell, the patients' NK cells failed to release active NKCF in the supernatant. However, the cells released NKCF after stimulation with the lectin Con A or a mixture of TPA and ionophore, albeit to a lesser extent than controls. These results suggested that AIDS and ARC NK cells are defective in the trigger involved in release of NKCF. Further studies were done to investigate whether the immunomodulator IL 2 can restore the functional activity of the defective NK cells. Treatment with IL 2 resulted in augmented NK cytolytic activity, but did not reach control levels of activated cells from normal controls. Furthermore, the patients' IL 2-treated cells recover partially the ability to be stimulated by NK cells and to release NKCF. These results suggest that the trigger for NKCF production and the cytolytic function of the patients' NK cells are regulated by IL 2. By delineating the stage at which the AIDS and ARC NK cells are defective, it is now possible to monitor their recovery and to investigate the effect of various biologic response modifiers in restoring NK activity.     

Activation of human peripheral blood-derived monocytes by OK-432 (Streptococcus pyogenes): augmented cytotoxicity and secretion of TNF and synergy with rIFN-gamma

The biological response modifier OK-432 has been shown both to exert the enhancement of several immunological activities and to have a direct anti-tumor effect. The present study examines the immunopotentiating effect of OK-432 on peripheral blood monocytes (PBM) derived from normal humans. Monocyte activation was assessed by examining direct cell-mediated cytotoxic activity (CMC) and secretion of cytotoxic factors in the supernatant by the 51Cr release assay and secretion of tumor necrosis factor (TNF)-alpha detected by a sensitive radioimmunoassay. The OK-432-augmented activity was compared to that achieved by recombinant interferon-gamma (rIFN-gamma). Coculture of PBM with OK-432 overnight resulted in significant augmentation of CMC and secretion of cytotoxic factors and TNF in the supernatant. The effects observed were dose dependent and the resulting activity was much more pronounced than that achieved with an optimal concentration of IFN-gamma. The monocyte- and supernatant-mediated cytotoxic activities were in a large part attributed to TNF as both activities were inhibited by anti-TNF antibody. Several parameters of monocyte activation by OK-432 were examined. The kinetics of monocyte activation revealed that a short time exposure (2-6 hr) was sufficient for activation but maximal activation was detected after 18 hr. However, the kinetics of the cytotoxic assay were not shortened and 16-20 hr was necessary for optimal cytotoxic activity. Significant synergy was obtained when suboptimal concentrations of OK-432 and IFN-gamma were used. The synergy was noted in CMC, supernatant activity, and TNF concentration. These results demonstrate that OK-432 is a potent activator of monocyte cytotoxicity and also activates secretion of TNF. Also, OK-432 is a much more potent activator than rIFN-gamma. The synergy with OK-432 and IFN-gamma suggests that OK-432-mediated activation of monocytes takes place by a different mechanism than that mediated by rIFN-gamma. Thus, monocytes and products thereof may actively participate in the in vivo anti-tumor effect mediated by OK-432.     

Effective Induction of Human NK Cells with OK-432 and Further Augmentation of Their Cytolytic Function by rIL-2

Low concentrations of exogenously added recombinant interleukin 2 (rIL-2) were able to augment OK-432-induced natural killer (NK) cell activity. This kind of augmenting effect depended on the dose of rIL-2 and manifested itself only in PBMC stimulated with OK-432 (OK-MC) followed by rIL-2; augmentation did not happen in the reverse order. The existence of CD16⁺/CD25⁺ (IL-2 receptor positive; IL-2R⁺) and CD57⁺/CD25⁺ double positive cells which possess NK cell surface markers in OK-MC markedly increased in a long-term culture (12 days). A strong positive correlation was observed between the IL-2-dependent augmentation of NK activity and the quantitative changes in cell populations that possessed NK cell phenotypes. Treatment of the day-12-OK-MC with monoclonal anti-CD56 antibody plus complement could almost completely abrogate the augmented NK cytotoxicity. Furthermore, this augmenting effect was detectable within 4 hr after addition of rIL-2 at single cell level, suggesting that the effect did not require NK cell's DNA synthesis. Thus it was suggested that OK-432 could promote and upregulate the expression of IL-2 receptor (CD25) on CD56⁺ NK cell populations. Moreover, it was considered that the interaction of low concentration rIL-2 with IL-2 receptors on OK-432-activated NK cells could augment their lytic function.     

Effect of altered membrane structure on NK cell-mediated cytotoxicity. III. Decreased susceptibility to natural killer cytotoxic factor (NKCF) and suppression of NKCF release by membrane rigidification

We have shown recently that alteration of the membrane fluidity of either effector or target cells results in significant and selective inhibition of NK cell-mediated cytotoxicity (NK CMC). However, the localization of the defective stage in the NK lytic pathway is not known. In the present study, we show that rigidification of the NK-sensitive U937 target cell membrane by lipid modulation reduces its sensitivity to lysis by NK cytotoxic factor (NKCF). This resistance was not due to loss of NKCF binding sites on the target cell because target cells with rigid membranes absorbed more NKCF than control cells. The enhanced ability to absorb NKCF by membrane modification was supported by data showing that NK-resistant Raji cells lacking NKCF-binding sites absorb NKCF after lipid modification. Furthermore, consistent with the lipophilic nature of NKCF, synthetic lipid vesicles absorb NKCF. In contrast to membrane rigidification, membrane fluidization of the target cell did not change the target cell properties. Rigidification of the NK effector cell membrane abrogates it ability to secrete active NKCF when stimulated by target cells or by mitogens. Membrane fluidization of the NK effector cells did not inhibit their ability to release NKCF. The results of these studies demonstrate that inhibition of NK CMC by rigidification of the target cell membrane results in cells that are inhibited in processing bound NKCF to lysis. Inhibition of NK CMC by rigidification of the NK effector cell results in defective trigger for activation of the NKCF release mechanism.     

An inducer of NKCF (NK cytotoxic factor) release: localization on target-cell membrane and initial characterization.

Natural killer (NK) cells are probably involved in the elimination of virus-infected cells and of certain tumor cells. NK cell-mediated cytotoxicity (NK-CMC) was extensively studied and was found to consist of several steps. Following recognition and conjugation between the effector and the target cell, the latter one induces release of NK cytotoxic factor (NKCF) from the effector cells. The NKCF binds to the target cell which is subsequently killed. None of the molecules involved in these steps was completely characterized. In the present study it is demonstrated that isolated membranes of target cells can effectively induce the release of NKCF. Furthermore, the activity of such isolated membranes was found to be modulated by interferon (IFN) treatment of the cells prior to membrane isolation. It was therefore concluded that an NKCF-inducing structure (NKIS) is present on plasma membranes and is distinct from the NK-recognition structure. Similarly, the sensitivity to NK-CMC could be transferred from sensitive cells to IFN-gamma-treated (NK-resistant) cells by membrane fusion with the aid of Sendai virus envelope glycoproteins. It is proposed that transfer of NKIS is responsible for the acquired sensitivity to NK-CMC. In addition, it is shown that NKIS activity was recovered following membrane solubilization and reconstitution. Its level on cell surface was modulated by treatment of cells with tunicamycin, thus indicating that NKIS was probably a cell surface glycoprotein.     

Analysis of rat natural killer cytotoxic factor (NKCF) produced by rat NK cell lines and the production of a murine monoclonal antibody that neutralizes NKCF

Natural killer cytotoxic factor (NKCF) is produced as a result of the interaction of murine, rat, or human natural killer (NK) cells with NK-susceptible targets. This factor has been linked to the target cell lysis mediated by the NK effector cell. In the present results, culture supernatants from rat large granular lymphocyte (LGL) tumors exhibited NKCF activity which lysed the susceptible targets, MBL-2 and YAC-1. NKCF production from these rat tumor lines was spontaneous and was not significantly increased by co-incubation of the LGL tumors with target cells, target cell membranes, or by preincubation of the LGL tumor cells with interferon or interleukin 2. In addition to NKCF activity, the supernatants lysed L929, indicating the presence of tumor necrosis factor (TNF) in these preparations. The presence of this latter cytokine was verified using specific antibodies to recombinant murine TNF which neutralized the L929 activity while not affecting the NKCF activity against MBL-2 or YAC-1. Mouse monoclonal antibodies (mAb) A0287, A0462, and A0316) which significantly inhibit the NKCF cytolytic activity of these LGL-derived supernatants were also produced. These antibodies were shown to cross-react with human NKCF in a manner similar to that seen in the rat. Interestingly these same mAb demonstrated no inhibition of L929 cytotoxicity from either LGL-derived supernatants or by recombinant murine or human TNF. To examine further the specificity of these antibodies, they were chemically linked to Sepharose 4B and found to remove a significant proportion of the NKCF cytolytic activity from LGL supernatants, while not affecting the TNF reactivities in these preparations. In addition, these antibodies demonstrated significant inhibition of cell-mediated cytotoxicity by rat LGL against YAC-1 target cells. Biochemical analysis of labeled NKCF-containing supernatants indicated the major protein recognized by these anti-NKCF mAb to be approximately 12,000 m.w. The use of these mAb against NKCF should be very useful in further purification and biochemical characterization of NKCF and in studying its role in a variety of cell-mediated cytotoxicity assays.     

Effectivein vivo induction of lymphokine-activated killer (LAK) cells by pretreatment with a streptococcal preparation,OK-432

Effects of a streptococcal preparation, OK-432, on precursors of lymphokine-activated killer (LAK) cells were observedin vivo. Total number of splenocytes and the ratio of asGM ₁ ⁺ cells increased gradually after i.v. administration of OK-432, reaching their peaks at 3 to 4 days. It was found that as GM ₁ ⁺ cells were nonadherent and large in size. There were little differences in the ratios of Thy-1⁺, Lyt-2⁺, and L3T4⁺ cells before and after OK-432 treatment. Mice were injected i.p. with recombinant interleukin 2 (rIL-2) at a dose of 5 × 10⁴ U per mouse 4 days after OK-432 administration and LAK activity in their splenocytes was examined using natural killer (NK) resistant EL-4 target cells. Splenocytes in mice treated with both OK-432 and rIL-2 showed higher LAK activity than those in mice treated with rIL-2 alone.In vivo treatment with anti asGM, antibody prior to rIL-2 injection abolished completely such augmentation of LAK activity in OK-432 treated mice. These results demonstrated that asGM ₁ ⁺ LAK precursor cells induced by OK-432 were effectively differentiated into LAK cells by rIL-2.     

Selective expansion and partial activation of human NK cells and NK receptor-positive T cells by IL-2 and IL-15.

IL-2 and IL-15 are lymphocyte growth factors produced by different cell types with overlapping functions in immune responses. Both cytokines costimulate lymphocyte proliferation and activation, while IL-15 additionally promotes the development and survival of NK cells, NKT cells, and intraepithelial lymphocytes. We have investigated the effects of IL-2 and IL-15 on proliferation, cytotoxicity, and cytokine secretion by human PBMC subpopulations in vitro. Both cytokines selectively induced the proliferation of NK cells and CD56(+) T cells, but not CD56(-) lymphocytes. All NK and CD56(+) T cell subpopulations tested (CD4(+), CD8(+), CD4(-)CD8(-), alphabetaTCR(+), gammadeltaTCR(+), CD16(+), CD161(+), CD158a(+), CD158b(+), KIR3DL1(+), and CD94(+)) expanded in response to both cytokines, whereas all CD56(-) cell subpopulations did not. Therefore, previously reported IL-15-induced gammadelta and CD8(+) T cell expansions reflect proliferations of NK and CD56(+) T cells that most frequently express these phenotypes. IL-15 also expanded CD8alpha(+)beta(-) and Valpha24Vbeta11 TCR(+) T cells. Both cytokines stimulated cytotoxicity by NK and CD56(+) T cells against K562 targets, but not the production of IFN-gamma, TNF-alpha, IL-2, or IL-4. However, they augmented cytokine production in response to phorbol ester stimulation or CD3 cross-linking by inducing the proliferation of NK cells and CD56(+) T cells that produce these cytokines at greater frequencies than other T cells. These results indicate that IL-2 and IL-15 act at different stages of the immune response by expanding and partially activating NK receptor-positive lymphocytes, but, on their own, do not influence the Th1/Th2 balance of adaptive immune responses.     

Correlation of protein kinase activation and testosterone production after stimulation of Leydig cells with luteinizing hormone.

The effect of different doses of luteinizing hormone on activation of protein kinases, cyclic AMP and testosterone production was studied in purified rat testis Leydig-cell preparations in the presence of 3-isobutyl-1-methylxanthine (a phosphodiesterase inhibitor). In addition, the nature of the protein kinases present in these cells and other tissues was investigated. The following results were obtained. 1. With all the amounts of luteinizing hormone used (0.1-1000 ng/ml), both activation of protein kinase and stimulation of testosterone production were demonstrated. With the lowest amount of luteinizing hormone (0.1 ng/ml), an 8.4+/-0.9% (S.E.M.,n=6) stimulation of protein kinase activation occurred, increasing to 100% with 1000 ng/ml, compared with 3.2+/-1.0%(S.E.M.,n=7) and 100% stimulation of testosterone production with 0.1 and 100 ng/ml respectively. 2. With amounts of luteinizing hormone up to 1 ng/ml (which gave half-maximal stimulation of testosterone production) no detectable increases in net cyclic AMP production were obtained. With higher amounts of luteinizing hormone, cyclic AMP production increased, but maximal production was not reached with 1000 ng/ml. 3. Two isoenzymic forms of protein kinase were present in Leydig cells and seminiferous tubules; type I was eluted with 0.075 M-and type II with 0.22-0.25 m-NaCl from DEAE-cellulose columns. 4. The protein kinase activity was not affected by the presence of erythrocytes in the Leydig-cell preparation, but varied depending on the type of histone used as substrate (histone F2b greater than mixed greater than histone F1).     

Stimulation of murine natural killer (NK) cells by a monoclonal antibody specific for the NK1.1 antigen. IL-2-activated NK cells possess additional specific stimulation pathways

NK cells lyse certain tumor cell targets but the effector cell surface molecules responsible for this reactivity remain uncertain. The allotypic NK1.1 Ag is the most specific serologic marker on murine cells that display non-MHC-restricted cytolysis of tumor cell targets, but no function has been previously ascribed to this Ag. In this report, we demonstrate that, in the presence of a mAb specific for the NK1.1 Ag (mAb PK136), freshly isolated and IL-2-activated NK cells from C57BL/6 mice can be induced to lyse an otherwise resistant target cell, Daudi. This phenomenon is effector and mAb specific because NK cells derived from BALB/c mice do not express the NK1.1 Ag and cannot be triggered by mAb PK136. We demonstrate that IL-2 activated but not freshly isolated NK cells express the Ly-6 and VEA Ag, originally described as T cell activation Ag. Moreover, mAb specific for Ly-6 and VEA induce target cell lysis by IL-2 activated but not freshly isolated NK cells. These mAb effects are specific, concentration dependent, and display kinetics that are similar to spontaneous cytolysis of NK-sensitive targets. The Fc portion of the activating antibodies and only FcR bearing target cells participate in mAb-induced activation, consistent with the mechanism of redirected lysis. Finally, analysis of Daudi cells transfected with beta 2-microglobulin gene demonstrate that the expression of MHC class I Ag by the target cell does not affect its sensitivity to mAb-induced lysis by NK cells. These data demonstrate that the NK1.1 Ag is functionally active on both freshly isolated and IL-2-activated NK cells and that IL-2-activated NK cells possess additional pathways of specific stimulation.     

Studies on the mechanism of natural killer cytotoxicity. II. coculture of human PBL with NK-sensitive or resistant cell lines stimulates release of natural killer cytotoxic factors (NKCF) selectively cytotoxic to NK-sensitive target cells

This investigation has employed the "innocent bystander" type of experimental design to determine whether soluble cytotoxic factor(s) are released during interactions between human peripheral blood lymphocytes (PBL) and NK-sensitive target cells. PBL cocultured with NK-sensitive Molt-4 or K562 target cells in the lower well of a miniaturized Marbrook culture released natural killer cytotoxic factors (NKCF), which diffused across a 0.2-mu Nucleopore membrane and lysed Molt-4 or K562 target cells cultured in the upper chamber. Coculture of PBL with the NK-resistant Raji or WI-L2 cell lines also induced release of NKCF. These factors were selectively cytotoxic to NK-sensitive targets and lysed Molt-4 and, to a lesser extent, K562 cells. However, Raji, WI-L2, and RPMI 1788 cells were all resistant to lysis. In addition, low density fractions from Percoll density gradients that were enriched for NK effector cells also released increased levels of NKCF during coculture with Molt-4 cells. Lysis of Molt-4 and K562 targets was observed after exposure to NKCF for 48 hr and 60 to 70 hr, respectively. Cellfree supernatants containing NKCF were obtained after a short time of incubation (i.e., within 5 hr of coculture of PBL with NK target cells). The factors were nondialyzable, stable at 56 degrees C for 3 hr, and showed partial loss of activity on storage at 4 degrees C or -20 degrees C for 7 days. These data suggest that NKCF may be involved in the lytic mechanism of human NK cell-mediated cytotoxicity.     

Mechanism of action of a streptococcal preparation (OK-432) in prevention of autoimmune diabetes in NOD mice. Suppression of generation of effector cells for pancreatic B cell destruction

We have previously reported that treatment with a streptococcal preparation (OK-432), one of the biologic response modifiers, inhibits insulitis and development of autoimmune diabetes in nonobese diabetic (NOD) mice and Bio-Breeding rats used as animal models of insulin-dependent diabetes mellitus (IDDM). We studied the mechanism by which OK-432 inhibited development of IDDM in NOD mice. In female NOD mice diabetes spontaneously developed from 10 to 15 wk of age and the cumulative incidence of diabetes amounted to 74.7% at 30 wk of age. NOD mice, however, never developed diabetes over the observation period of up to 45 wk of age when they were i.p. injected with 0.1 mg of OK-432 weekly from 4 to 15 wk of age. OK-432 treatment in younger age had a stronger inhibitory effect on the development of diabetes. Diabetes was transferred to young, irradiated mice by spleen cells of nontreated, adult mice, but barely transferred by those of OK-432-treated mice. Furthermore, these spleen cells of OK-432-treated mice did not suppress transfer of diabetes by diabetic mice spleen cells. Treatment with cyclophosphamide promoted development of diabetes in nontreated NOD mice due to removal of suppressor cells. However, cyclophosphamide did not show the promotive effect in OK-432-treated mice. Taken together, these results indicate that OK-432 treatment prevented development of diabetes mainly by suppression in generation of the effector cells for pancreatic B cell destruction. The same OK-432 treatment did not suppress the immune response to exogenous AG such as xenogeneic SRBC and allogeneic tumor cells. The study suggests that BRM in the natural environment such as streptococci may suppress induction and progression of autoimmunity and be useful for the immunotherapy of human IDDM.     

Studies on the mechanism of natural killer cytotoxicity. III. Activation of NK cells by interferon augments the lytic activity of released natural killer cytotoxic factors (NKCF)

The mechanism by which interferon (IFN) pretreatment of effector cells augments natural killer (NK) cell-mediated cytotoxicity (CMC) was examined by determining whether IFN has any effect on the production of natural killer cytotoxic factors (NKCF). NKCF are released into the supernatant of co-cultures of murine spleen cells and YAC-1 stimulator cells, and their lytic activity is measured against YAC-1 target cells. It was demonstrated that pretreatment of effector cells with murine fibroblast IFN or polyinosinic-polycytidylic acid (pIC) resulted in the release of NKCF with augmented lytic activity. Evidence indicated that the IFN-induced augmentation of NKCF activity required protein synthesis during the IFN pretreatment period, because concurrent pretreatment with both IFN and cycloheximide abrogated the IFN effect. Protein synthesis, however, is not required for the production of base levels of NKCF because emetine pretreatment of normal spleen cells did not result in a decrease in NKCF production. Furthermore, substantial levels of NKCF activity could be detected in freeze-thaw lysates of freshly isolated spleen cells. Cell populations enriched for NK effector cells, such as nylon wool-nonadherent nude mouse spleen cells, produced lysates with high levels of NKCF activity, whereas lysates of CBA thymocytes were devoid of NKCF activity. Pretreatment of spleen cells with either IFN or pIC resulted in an augmentation of the NKCF activity present in their cell lysates. Taken altogether, these findings suggest that freshly isolated NK cells contain preformed pools of NKCF. Pretreatment of these cells with IFN causes de novo synthesis of additional NKCF and/or activation of preexisting NKCF. According to our model for the mechanism of NK CMC, target cell lysis is ultimately the result of transfer of NKCF from the effector cell to the target cell. The evidence presented here suggests that the IFN-induced augmentation of NK activity could be accounted for by an increase in the synthesis, activation, and/or release of NKCF.     

Thymic hormones and prostaglandins. I. Lack of stimulation of prostaglandin production by thymic hormones

Prostaglandins (PGs) have been implicated as possible mediators of the biological activity of thymic hormones. It has been shown that type E-PGs are able to mimic the action of several thymic hormones and that indomethacin prevents in vivo or in vitro the appearance of Thy-1⁺ antigen induced by some of these factors. We thus investigated a possible role for PGs in the mechanism of action of different thymic extracts and peptides. Attempts to modulate prostaglandin production showed that neither thymosin fraction 5 (0.01 – 100 μg/ml), nor thymosin α 1 (1–10 μg/ml), thymulin (0.001–100 ng/ml), thymopoietin II (10 – 1000 ng/ml) or TP5 (10 – 1000 ng/ml) affect PGE2, 6-keto-PGF1 α, PGF2 α and TXB2 production by spleen cells from control and thymectomized mice. These results do not support the hypothesis that prostaglandins could act as mediators of thymic hormones.     

Regulation of lipopolysaccharide-induced granulopoiesis and macrophage formation by spleen cells. I. Relationship between colony-stimulating factor release and lymphocyte activation in vitro.

Addition of bacterial lipopolysaccharide (LPS), a B cell mitogen, to mouse spleen cultures strongly stimulated production of colony-stimulating factor (CSF), the humoral regulator of granulopoiesis, and macrophage formation in vitro. Secretion of CSF from LPS-stimulated spleen cells coincided with cellualr DNA synthesis and cell transformation and both activities could be attributed to the lipid A moiety of the molecule. Different experimental approaches were used to study the relationship of CSF release and lymphocyte activation in response to LPS: a) modification of LPS with polymyxin B, an antibiotic bactericidal for most Gram-negative bacteria, caused a marked reduction in mitogenic activity, although the ability to induce CSF was not significantly altered; b)spleen cells from CBA/N mice, a mutant strain with an x-linked genetic defect in immunologic and mitogenic responses to polyclonal activators including LPS, showed diminished mitogeinc responses; however, high levels of CSF were produced; c) mitotic and DNA inhibitors (colchicine and cytosine arabinoside) did not affect CSF release although they completely inhibited mitogenicity. Thus, the spleen cell population participating in the process of LPS-induced CSF generation is probably a nondividing, terminally differentiated one without need for DNA synthesis. In addition, it was also shown that active RNA and protein synthesis are needed in this process.