Soluble Fc gamma receptors: interaction with ligands and biological consequences

Soluble Fc gamma receptors are produced by cleavage of the membrane receptors or by alternative splicing. They are found in biologic fluids. After a brief description of the structure and mode of production of soluble Fc gamma R, we address the question of ligands and function of the soluble Fc gamma R by using recombinant molecules and transgenic animals. We show that soluble Fc gamma R are not only IgG-binding factors which interfere with, and block, Fc-dependent immune reactions but also molecules that interact, in vitro, with non-Ig-ligands such as CR3 and CR4 and are trigger or regulate immune functions via these receptors.

Functions of Fc receptors on human dendritic Langerhans cells

Immature dendritic cells are antigen presenting cells highly specialized for capturing and processing foreign protein antigens. These cells express Fc gamma RII and Fc epsilon RI which, by their ability to internalize and use the endocytic pathway, increase their capacity to process antigens. Immature dendritic cells, such as epidermal Langerhans cells, also release soluble forms of Fc gamma RII. These latter molecules are likely to compete with the membrane-associated Fc gamma R to diminish or abrogate the capacity of dendritic cells to present immune complexes, as suggested by our in vitro experiments using both human and mouse epidermal Langerhans cells. However, when dendritic cells mature in vitro and become efficient stimulators of resting T cells, they rapidly down-regulate and sometimes completely abolish the expression of their membrane-associated Fc gamma R and Fc epsilon RI. Consequently, they lose or at least strongly diminish their capacity to capture immune complexes. At this stage, the release of soluble Fc gamma R by dendritic cells is also markedly diminished. One can hypothesize that the membrane-associated Fc gamma RII and the soluble Fc gamma RII are molecules expressed when dendritic cells are potent capturing and processing cells, the soluble Fc gamma RII molecule acting by competition as a negative regulatory element on the Fc gamma RII-mediated internalization of IgG-containing immune complexes. Thus, the expression of membrane-associated Fc gamma R and Fc epsilon RI, as well as the release of soluble Fc gamma R, would seem to characterize the immature stage of dendritic cells.

Cytokines and cancer

The relationships between cytokines and cancer are multiple and bidirectional. On the one hand, cytokines may directly influence carcinogenesis and metastasis by modifying the tumor phenotype. On the other hand, during tumor progression, modifications of the cytokine expression in the tumor environment may be induced by the tumor cells, leading to a state of immunosuppression reflected by low cytokine expression in tumor stroma. Cytokines also play a role by stimulating the host immune system to generate anti-tumor specific responses. Finally, the use of cytokines as anti-tumor agents has led to objective clinical responses in about 15-25% of patients with metastatic melanoma or renal cell carcinoma, which presents the basis for the development of promising immunotherapeutic approaches for cancer therapy.

Identification of the cleavage site involved in production of plasma soluble Fc gamma receptor type III (CD16)

CD16 (FcgammaR type III) is a low-affinity IgG Fc receptor (R) that exists in two isoforms, a transmembrane FcgammaRIIIa expressed by NK cells and monocytes, and a phosphatidylinositol-linked FcgammaRIIIb expressed by neutrophils. A soluble form of CD16 (sCD16) circulates in plasma. The cleavage site and the nature of the enzyme(s) involved in production of sCD16 were investigated. Soluble CD16 was purified to apparent homogeneity from human serum by eight steps, including anion exchange and immunoaffinity chromatography. Serum sCD16 was sequenced at both ends, as well as a recombinant form of sCD16 used as control. N-terminal sequencing demonstrated that serum sCD16 originates from neutrophil FcgammaRIIIb and C-terminal sequencing suggested that the cleavage site is between Val 196 and Ser 197, close to the membrane anchor. Addition of a hydroxamate-based inhibitor of Zn2+ metalloproteinases (RU36156) led to a dramatic decrease of sCD16 production by phorbol 12-myristate 13-acetate-activated neutrophils, whereas inhibitors of serine proteinases had no significant effect, showing the metalloproteinase dependence of this cleavage process.

Highly resolved chemical imaging of living cells by using synchrotron infrared microspectrometry

Using synchrotron radiation as an ultra-bright infrared source, we have been able to map the distributions of functional groups such as proteins, lipids, and nucleic acids inside a single living cell with a spatial resolution of a few microns. In particular, we have mapped the changes in the lipid and protein distributions in both the final stages of cell division and also during necrosis.

Intracellular expression of an antibody fragment-neutralizing p21 ras promotes tumor regression

Mutated ras genes are found in a large number of human tumors and, therefore, constitute one of the primary targets for cancer treatment. Microinjection of the neutralizing anti-Ras monoclonal antibody Y13-259 was previously reported to induce transient phenotypic reversion of ras-transformed rodent fibroblasts in vitro. We have prepared a single-chain Fv fragment (scFv) derived from Y13-259, and here, we show that intracellular expression of the scFv led to the specific inhibition of the Ras signaling pathway in Xenopus laevis oocytes and NIH3T3 fibroblasts. Moreover, neutralizing Ras with the scFv specifically promoted apoptosis in vitro in human cancer cells but not in untransformed cells. As a step toward cancer gene therapy, we finally demonstrated that intratumor transduction of HCT116 colon carcinoma cells with the anti-Ras scFv using an adenoviral vector elicited sustained tumor regression in nude mice.

Identification of two quantitative trait loci involved in antibody production on mouse chromosome 8

Several quantitative trait loci (QTLs) contributing to the extreme phenotypes of the selected high (H) and low (L) antibody-responder lines of mice were mapped on distinct chromosomes. Successive backcrosses were bred to reduce the length of the QTL-bearing segment detected on chromosome 8 and to produce congenic lines to test gene effect independently of the other QTLs. An increase in antibody responses was repeatedly found to be associated with inheritance of the H-line allele at two markers separated by 30 cM on that chromosome. In the successive backcrosses, background and unlinked involved genes of H-line origin were progressively eliminated; however, unexpected within-progeny variations persisted in the third and even fourth backcross. Nevertheless, the presence of two QTLs within the considered interval was definitely demonstrated in distinct progenies of the fourth backcross which separately inherited one of the two gene-marker H-line alleles. The previously identified chromosome 8 segment therefore contains at least two QTLs involved in antibody responsiveness.

p53 status does not predict initial clinical response to bacillus Calmette-Guerin intravesical therapy in T1 bladder tumors

PURPOSE

In superficial urothelial tumors of the bladder, p53 status is currently the most informative pretreatment parameter to define a population at higher risk for invasive carcinoma. Also, in T1 tumors, occurrence of muscular invasion is often related to an early relapse following BCG therapy. With the knowledge of biological parameters able to identify the group of initial BCG therapy non-responders, it would be possible to offer earlier treatment to the patients who need a more aggressive mode of therapy. The aim of this work was to study the predictive value of the p53 tumor status on the early BCG therapy response.

MATERIALS AND METHODS

The population included a selected group of 43 patients presenting T1 bladder tumors with no carcinoma in situ (Tis), treated by transurethral resection (TUR) followed by intravesical BCG therapy. Clinical outcome was analyzed in relation to usual clinical and histopathological parameters, and pretreatment p53 tumor status was assayed by an immunohistochemical technique using DO7 monoclonal antibody. For 16 specimens, p53 gene was investigated using a Single Strand Conformation Polymorphism (SSCP) analysis and sequence determination.

RESULTS

p53 anomalies were strongly correlated to smoking behavior (p = 0.003) and tumoral grade (p = 0.025). Univariate analysis revealed an absence of correlation between p53 immunostaining and initial, one and two years response-rate to BCG therapy. However, longterm followup revealed a trend between positive staining and disease progression. The p53 molecular study validated the use of DO7 immunostaining in detection of p53 anomalies.

CONCLUSIONS

In T1 bladder tumors, pretreatment p53 determination was not useful to define a group of early BCG non-responders. Thus, p53 status and immunological response induced by BCG endovesical therapy are two independent events.

Prognostic value of intratumoral interferon gamma messenger RNA expression in invasive cervical carcinomas

BACKGROUND

The production of the cytokine interferon gamma (IFN gamma) by activated peripheral blood mononuclear cells may be reduced in patients with invasive cervical carcinoma. This study was designed to assess the prognostic value of intratumoral IFN gamma messenger RNA (mRNA) levels in such patients.

METHODS

Biopsy specimens of primary cervical lesions were obtained from 27 patients with invasive squamous cell carcinoma before they received any therapy. Two prognostic groups were considered: 1) a group of 14 patients who had no apparent disease recurrence and who were alive 2 years after diagnosis (good-prognosis group) and 2) a group of 13 patients who had disease recurrence or died during the 2-year follow-up (poor-prognosis group). A competitive reverse transcription-polymerase chain reaction assay was used to measure levels of IFN gamma and beta actin mRNA. The expression of human leukocyte antigen (HLA) class II proteins (which is stimulated by IFN gamma) in tumor cells was studied by immunostaining.

RESULTS

Tumor specimens from all 14 patients in the good-prognosis group contained more than 10(3) IFN gamma mRNA copies per 5 x 10(5) beta actin mRNA copies, whereas tumor specimens from only six of the 13 patients in the poor-prognosis group contained this level of IFN gamma mRNA (two-sided P = .006). No clear relationship was observed between levels of IFN gamma mRNA and T-cell or natural killer cell infiltration in tumors; however, a statistically significant association was observed between HLA class II expression on tumor cells and IFN gamma mRNA levels (two-sided P = .01).

CONCLUSIONS

A subgroup of poor-prognosis cervical carcinoma patients who have low levels of intratumoral IFN gamma mRNA was identified.

A tyrosine-based signal present in Ig alpha mediates B cell receptor constitutive internalization

B lymphocytes express Ag receptors (BCR) that are composed of ligand binding subunits, the membrane Igs, associated with Ig alpha/Ig beta heterodimers. One main BCR function is to bind and to internalize Ags. Peptides generated from these internalized Ags may be presented to T lymphocytes. Here, we have analyzed the involvement of BCR Ig alpha/Ig beta components in BCR constitutive endocytosis. The role of Ig alpha subunit in BCR constitutive endocytosis was first determined in the context of an IgM-based BCR. In contrast with BCR that contain wild-type Ig alpha, surface BCR lacking Ig alpha cytoplasmic domain were not constitutively internalized. The respective roles of Ig alpha and Ig beta subunits were then analyzed by expressing chimeric molecules containing the cytoplasmic domains of either subunits in a B cell line. Only the Ig alpha cytoplasmic domain contained an internalization signal that allowed constitutive endocytosis of Ig alpha chimeras via coated pits and accumulation in sorting-recycling endosomes. This internalization signal is contained in its immunoreceptor tyrosine-based activation motif. These results indicate that Ig alpha, through its immunoreceptor tyrosine-based activation motif, may account for the ability of IgM/IgD BCR to constitutively internalize monovalent Ags.

Fc epsilon receptor I-associated lyn-dependent phosphorylation of Fc gamma receptor IIB during negative regulation of mast cell activation

Fc gamma RIIB are low-affinity receptors for IgG whose intracytoplasmic domain contains an immunoreceptor tyrosine-based inhibition motif (ITIM). Fc gamma RIIB inhibit cell activation triggered by receptors that signal via immunoreceptor tyrosine-based activation motifs. This inhibition requires ITIM tyrosyl phosphorylation and is correlated with the binding of SH2 domain-containing phosphatases that may mediate the inhibitory signal. In the present work, we investigated the mechanism of Fc gamma RIIB phosphorylation and its consequences in mast cells. We demonstrate that the phosphorylation of Fc gamma RIIB requires coaggregation with Fc epsilon RI and that, once phosphorylated, Fc gamma RIIB selectively recruit the inositol polyphosphate 5 phosphatase SHIP, in vivo. In vitro, however, the phosphorylated Fc gamma RIIB ITIM binds not only SHIP, but also the two protein tyrosine phosphatases, SHP-1 and SHP-2. We show that the coaggregation of Fc gamma RIIB with Fc epsilon RI does not prevent Fc epsilon RI-mediated activation of lyn and syk. Both kinases can phosphorylate Fc gamma RIIB in vitro. However, when coaggregated with Fc epsilon RI, Fc gamma RIIB was in vivo phosphorylated in syk-deficient mast cells, but not in lyn-deficient mast cells. When Fc epsilon RI are coaggregated with Fc gamma RIIB by immune complexes, Fc epsilon RI-associated lyn may thus phosphorylate Fc gamma RIIB. By this mechanism, Fc epsilon RI initiate ITIM-dependent inhibition of intracellular propagation of their own signals.

Chemical imaging of nucleic acids, proteins and lipids of a single living cell. Application of synchrotron infrared microspectrometry in cell biology

Hybridoma B-cells have been used as models to evaluate the performance of synchrotron infrared microscopy to obtain chemical images of a single living cell. Chemical mapping of nucleic acids, proteins and lipids at a resolution of a few microns, close to the diffraction limit in the mid-infrared region are shown.

[Fas, fas ligand, immune tolerance, and cancer: implications in cancer of the colon]

Fas and Fas ligand (FasL) are implicated in programmed cell death or apoptosis. In the immunological field, they are particularly important in auto-immunity, graft rejection and anti-tumoral response. Fas ligand expression on thymocytes, activated T lymphocytes, and in sites of immune privilege, suggests the importance of Fas/FasL interactions in negative control of the immune response. The recent description of FasL expression by tumoral cells, represents a new mechanism of immune escape for different cancer, and has been well studied in colon adenocarcinoma.

A new set of monoclonal antibodies against human Fc gamma RII (CD32) and Fc gamma RIII (CD16): characterization and use in various assays

Four mouse anti-human Fc gamma RII (CD32) (6C4, 2B2, 3D3, 93.4) (IgG1, kappa) and one anti-human Fc gamma RIII (CD16) (7.5.4) IgG1, kappa) MAbs were raised. An in vitro switch variant, 7.5.4Sw50 (IgG2b, kappa), was also derived from the 7.5.4 MAb. 6C4, 2B2, and 3D3 MAbs bind both Fc gamma RIIa and Fc gamma RIIb isoforms. Two of them (6C4 and 2B2 MAbs) allow a complete blockade of the binding of immune complexes to Fc gamma RII. All three MAbs immunoprecipitate the receptor and bind both its glycosylated and nonglycosylated forms. The fourth anti Fc gamma RII MAb, 93.4, directed against the intracellular region of Fc gamma RIIa1/2, allows its detection by Western blotting only when it is not phosphorylated. The 7.5.4 MAb binds both Fc gamma RIIIa and Fc gamma RIIIb, can be used in Western blotting and does not inhibit aggregated IgG binding. ELISA using IV.3 (anti-Fc gamma RIIa1/2)/6C4 and 3G8 (anti-Fc gamma RIIIa/b)/7.5.4Sw50 MAb pairs make it possible to detect soluble Fc gamma RIIa1/2 and Fc gamma RIII, with a sensitivity of 200 pg/mL and 1 ng/mL, respectively. Surface plasmon resonance analyses indicated that the KD of two of the three anti-Fc gamma RII and of the anti-Fc gamma RIII are in the same order of magnitude (6C4: 0.78 nM, 2B2: 0.28 nM, 7.5.4: 0.47 nM). The anti-Fc gamma RII 3D3 MAb exhibits an off-rate constant higher than the 6C4 and 2B2 MAbs and a KD of 2.19 nM.

Effect of TGF-beta1 on cell cycle regulatory proteins in LPS-stimulated normal mouse B lymphocytes

The cell cycle events accompanying TGF-beta1-induced growth arrest of normal mouse resting B lymphocytes stimulated by LPS were investigated. We showed that TGF-beta1 prevents the retinoblastoma protein (pRb) phosphorylation and induces growth arrest in mid- to late G1. To explore the molecular basis of the effect of TGF-beta1, we analyzed the in vitro kinase activities of cyclin/cyclin-dependent kinase (cdk) complexes involved in the progression through G1 phase and in the G1/S transition, by using the glutathione S-transferase-pRb fusion protein as a substrate. Cdk2-associated kinase activity was strongly induced in mitogen-treated B cells. It was dramatically inhibited by TGF-beta1 as were the cyclin E- and cyclin A-dependent kinase activities. TGF-beta1 treatment had no significant effect on the expression of two G1/S phase proteins, cyclin E and cdk2. In contrast, the appearance of cyclin A, occuring in late G1 phase, was almost totally inhibited by TGF-beta1. We also showed that expression of the cdk inhibitor protein p27Kip1 decreased as cells progressed through the G1 phase. An accumulation of p27 was found in TGF-beta1-treated cells, showing that TGF-beta1 prevented LPS-induced decline of p27. Finally we found that the lack of kinase activity associated with cyclin E/cdk2 complexes was correlated with increased amounts of cdk2- and cyclin E-bound p27. Overall, these results suggest that both cyclin A and cdk2 may be active participants in the TGF-beta1-induced cell cycle arrest in normal mouse B cells and indicate the involvement of p27 in this mechanism.

Effect of TGF-beta1 on cell cycle regulatory proteins in LPS-stimulated normal mouse B lymphocytes

The cell cycle events accompanying TGF-beta1-induced growth arrest of normal mouse resting B lymphocytes stimulated by LPS were investigated. We showed that TGF-beta1 prevents the retinoblastoma protein (pRb) phosphorylation and induces growth arrest in mid- to late G1. To explore the molecular basis of the effect of TGF-beta1, we analyzed the in vitro kinase activities of cyclin/cyclin-dependent kinase (cdk) complexes involved in the progression through G1 phase and in the G1/S transition, by using the glutathione S-transferase-pRb fusion protein as a substrate. Cdk2-associated kinase activity was strongly induced in mitogen-treated B cells. It was dramatically inhibited by TGF-beta1 as were the cyclin E- and cyclin A-dependent kinase activities. TGF-beta1 treatment had no significant effect on the expression of two G1/S phase proteins, cyclin E and cdk2. In contrast, the appearance of cyclin A, occuring in late G1 phase, was almost totally inhibited by TGF-beta1. We also showed that expression of the cdk inhibitor protein p27Kip1 decreased as cells progressed through the G1 phase. An accumulation of p27 was found in TGF-beta1-treated cells, showing that TGF-beta1 prevented LPS-induced decline of p27. Finally we found that the lack of kinase activity associated with cyclin E/cdk2 complexes was correlated with increased amounts of cdk2- and cyclin E-bound p27. Overall, these results suggest that both cyclin A and cdk2 may be active participants in the TGF-beta1-induced cell cycle arrest in normal mouse B cells and indicate the involvement of p27 in this mechanism.

Affinity of the interaction between Fc gamma receptor type III (Fc gammaRIII) and monomeric human IgG subclasses. Role of Fc gammaRIII glycosylation

Binding of the Fc region of IgG antibodies to low affinity Fc gamma receptors (Fc gammaR) triggers important effector functions in the immune system. The type IIIb Fc gammaR (Fc gammaRIIIb or CD16) is a heavily glycosylated protein anchored to the membrane of neutrophils by a glycosylphosphatidylinositol link. This receptor contributes to cell activation by IgG immune complexes. To better understand the nature of the ligand-receptor association, we have studied the affinity and kinetics of the interaction between human IgG subclasses and two soluble forms of Fc gammaRIIIb (sFc gammaRIIIb or sCD16) corresponding to the 188 N-terminal amino acids of the extracellular region of the receptor, a glycosylated one made in eucaryotic cells (euc.sCD16) and a non-glycosylated one (proc.sCD16) made in Escherichia coli. Experiments using a BIAcore instrument, to measure protein binding in real time, showed that monomeric human IgG1 and IgG3, but not IgG2, IgG4, IgA and divalent antigen-binding fragments (F(ab')2) of IgG1, bound to immobilized euc.sCD16 with an affinity constant (K(A)) of 1.3 +/- 0.6 x 10(6) M(-1) and 2.6 +/- 0.4 x 10(5) M(-1), respectively. The affinity constant of proc.sCD16 for human IgG1 was in the same range (1.1 +/- 0.2 x 10(6) M(-1)), whereas that for human IgG3 was twofold higher (4.2 +/- 0.4 x 10(5) M(-1)). The specificity of the non-glycosylated receptor for human IgG subclasses bound to Sepharose was IgG1 > IgG3 >> IgG4 >>> IgG2. Thus, the extracellular polypeptide of Fc gammaRIIIb dictates the interaction of the receptor with IgG subclasses although glycosylation plays an inhibitory role in the interaction with human IgG3.

Generation and characterization of a mouse single-chain antibody fragment specific for disialoganglioside (GD2)

Anti-disialoganglioside (GD2) monoclonal antibodies (MAbs) have been used in vivo for immunolocalization and in phase I and II trials to target disseminated neuroblastoma, the most common extracranial solid tumor in children. However, the efficacy of these first-generation MAbs is likely to be improved by using engineered anti-GD2 antibodies. The generation of single-chain antibody fragments (scFv) could be very helpful as these molecules can be further modified to produce recombinant molecules with pre-defined properties such as immunotoxins, chimeric, or bispecific antibodies. Thus, a scFv directed against GD2 (scFv 7A4) was cloned, sequenced, and expressed. Its binding properties were characterized and compared to that of the parental MAb 7A4. Nucleotide sequence analysis of the scFv 7A4 indicated that its VH region belongs to the V region IIID subgroup and the V kappa to the V region II subgroup. The scFv 7A4 bound to GD2+ neuroblastoma cell lines but not to GD2- cell lines or to GD2- cells isolated from peripheral blood. ELISA and thin-layer chromatography (TLC) indicated that it retained the anti-GD2 specificity, and exhibited a slight cross-reaction with GD3 as the parental MAb. This scFv makes it possible to develop new useful reagents through genetic engineering for adjuvant tumor therapy.

Characterization of soluble gp130 released by melanoma cell lines: A polyvalent antagonist of cytokines from the interleukin 6 family

gp130 acts as a common transducing signal chain for all receptors belonging to the interleukin (IL)-6 receptor family. The IL-6-related cytokines [IL-6, IL-11, oncostatin M (OSM), leukemia inhibitory factor, ciliary neurotrophic factor, and cardiotrophin] often modulate tumor phenotype and control the proliferation of many tumor cell lines. We demonstrate that melanoma cell lines release, in vitro and in vivo (when transplanted in nude mice), soluble gp130 (sgp130), a potential antagonist of cytokines from the IL-6 family. Biochemical analysis revealed that sgp130 derived from melanoma patients' sera or from culture supernatants of melanoma cell lines is a Mr 104,000 protein that resolved after deglycosylation as a Mr 58,000 protein. PCR and Northern blot analysis only identified one gp130 membrane mRNA, suggesting that the soluble form of gp130 is generated by proteolytic cleavage. OSM reproducibly increases sgp130 released by melanoma cell lines, whereas leukemia inhibitory factor stimulates the production of sgp130 in only one of three cell lines tested. This tumor-derived sgp130 is functional because it binds in solution to the IL-6-soluble IL-6 receptor (gp80) complex. Recombinant sgp130 inhibits the growth inhibitory activity of the IL-6-soluble IL-6 receptor complex and OSM on some melanoma cell lines. Therefore, this soluble gp130 represents a natural antagonist of cytokines from the IL-6 family.

IL-6 is a survival prognostic factor in renal cell carcinoma

It has been reported that a high plasmatic concentration of interleukin-6 (IL-6) is correlated to a lack of response to immunotherapy in several malignancies, suggesting that IL-6 was either a marker of tumour aggressiveness or had only a predictive value of response to immunotherapy. To discriminate between these two possibilities, a retrospective study was performed in a series of 19 patients with metastatic renal cell carcinoma who did not respond to IL-2/IFNalpha/5-FU treatment. Serum levels of IL-6, C-reactive Protein (CRP), soluble IL-2-receptor (sIL-2R), M-CSF and neopterin were assayed before treatment. IL-6 showed a significant correlation with patients median survival time (P < 0.016), suggesting that serum concentration of IL-6 before treatment is a marker of tumour aggressiveness rather than a predictive parameter for an immunological response.

Soluble Fcgamma receptor, Fc gammaRIIa2, is present in two forms in human serum and is increased in patients: with stage C chronic lymphocytic leukemia

Human Fcgamma receptor type II (FcgammaRII/CD32) can be produced in a soluble form, termed FcgammaRIIa2, which contains the extra- and intracellular regions of the receptor, due to an alternative splicing of the transmembrane domain-encoding exon. We show that human sera contain two forms of FcgammaRIIa2. A full-length secreted protein, which has a 32 kDa backbone, can be detected only in some sera while all sera contain a C-terminal truncated form, lacking part of the intracytoplasmic tail, and exhibiting a 24 kDa protein backbone. The 24 kDa form is significantly increased in sera from stage C patients with B chronic lymphocytic leukemia, compared to healthy donors, stage A and B CLL patients, or CLL patients in complete remission.

The use of cytokines in the treatment of solid tumours

This manuscript reviews the clinical trials with cytokines in solid tumors. Starting with Interleukin 2 alone or in association with other cytokines and chemotherapy, the reviews opens the prospects of future direction for the use of cytokines as adjuvant therapy, for vaccination or to inhibit the growth activity of certain cytokines.