Modulation of the Human T Cell Response by a Novel Non-Mitogenic Anti-CD3 Antibody

The agonistic anti-human CD3ε antibody (Ab), OKT3, has been used to control acute transplant rejection. The in vivo administration of OKT3 was previously shown to induce the partial depletion of T cells and unresponsiveness (anergy) in the remaining CD4⁺ T cells. However, this therapy is also associated with the systemic release of several cytokines, which leads to a series of adverse side effects. We established a novel anti-human CD3ε Ab, 20-2b2, which recognized a close, but different determinant on the CD3ε molecule from that recognized by OKT3. 20-2b2 was non-mitogenic for human CD4⁺ T cells, could inhibit the activation of T cells in vitro, and induced T cell anergy in in vivo experiments using humanized mice. Cytokine release in humanized mice induced by the administration of 20-2b2 was significantly less than that induced by OKT3. Our results indicated that the CD3ε molecule is still an attractive, effective, and useful target for the modulation of T cell responses. The establishment of other Abs that recognize CD3ε, even though the determinant recognized by those Abs may be close to or different from that recognized by OKT3, may represent a novel approach for the development of safer Ab therapies using anti-CD3 Abs, in addition to the modification of OKT3 in terms of the induction of cytokine production.     

Lysis of fresh human solid tumor cells by autologous lymphocytes activated in vitro by allosensitization

Summary We have previously demonstrated that cancer patients' peripheral blood lymphocytes (PBL) allosensitized against single or pool normal donor PBL are capable of lysing fresh autologous tumor cells in a 4-h ⁵¹Cr-release assay. In this report, we present further investigations into this phenomenon. These alloactivated killer cells (A-AK cells) lysed autologous and allogeneic tumors and allogeneic but not autologous PBL. Furthermore, cold target inhibition studies demonstrated that autologous and allogeneic tumors were lysed by the same effector cells. Multiple metastases from the same patient were equivalently lysed by these A-AK cells. The presence of adherent cells and proliferation of the precursors were necessary to generate A-AK cells, although the effector cell itself was radioresistant and nonadherent. The effects of allosensitization were enhanced by the addition of lectin-free interleukin-2 preparations to the in vitro culture by partial depletion of adherent cells prior to sensitization. The A-AK effector cell was OKT3+, OKT8+, OKT4–, OKM1– and could be generated by just 3 days of allosensitization. The precursors for A-AK cells could be separated from NK cells on percoll gradients and lysis could be generated from thoracic duct lymphocytes, a population devoid of NK cells. The phenotype of the majority of the precursor cells was OKT3+, OKT4–. These allocatived PBL could be expanded in crude or lectin-free interleukin-2 without loss of cytotoxicity for fresh autologous tumor cells. Activated T cells represent a population of non-NK cells with broad lytic specificity for fresh tumor cells. Such cells may be of value in the adoptive immunotherapy of human solid tumors and may play a role in immune surveillance.     

Cytokine profiles in early rejection following OKT3 treatment in liver transplant patients

OKT3 , a murine monoclonal antibody specific to the human CD3 complex, induces immunosuppression by depletion of T cells. Administration of OKT3 results in significant release of proinflammatory cytokines, such as TNFalpha and IL1beta. Liver recipients who experience rejection within 3 weeks after transplantation with OKT3 prophylaxis recover their T cells by postoperative day 10 despite complete initial clearance. We sought to analyze the role of proinflammatory and Th-1 cytokines in T cell recovery and rejection after liver transplantation with OKT3 prophylaxis. In plasma samples from 32 patients, we measured TNFalpha, IL1beta and IL6 (before transplant and on postoperative days 1, 2 and 3) and IL2, IFNgamma, sIL2R and slCAM (postoperative days 5, 7 and 10) and examined possible correlations with T-cell recovery and occurrence of rejection within 3 weeks. TNFalpha, IL1beta, and IL6 did not correlate with T-cell recovery. In patients who rejected, IL2 and IFNgamma on postoperative days 5 and 7 correlated with degree of T-cell recovery by day 10; a significant rise in sIL2R over time also correlated with T-cell recovery in this group. Our results emphasize the role of Th-1 cytokines in rejection following OKT3 induction and suggest that markers of T cell activation may predict risk.     

TGN1412 Induces Lymphopenia and Human Cytokine Release in a Humanized Mouse Model

Therapeutic monoclonal antibodies (mAbs) such as the superagonistic, CD28-specific antibody TGN1412, or OKT3, an anti-CD3 mAb, can cause severe adverse events including cytokine release syndrome. A predictive model for mAb-mediated adverse effects, for which no previous knowledge on severe adverse events to be expected or on molecular mechanisms underlying is prerequisite, is not available yet. We used a humanized mouse model of human peripheral blood mononuclear cell-reconstituted NOD-RAG1^-/-Aβ^-/-HLADQ^{(tg+ or tg-)}IL-2Rγc^-/- mice to evaluate its predictive value for preclinical testing of mAbs. 2–6 hours after TGN1412 treatment, mice showed a loss of human CD45⁺ cells from the peripheral blood and loss of only human T cells after OKT3 injection, reminiscent of effects observed in mAb-treated humans. Moreover, upon OKT3 injection we detected selective CD3 downmodulation on T cells, a typical effect of OKT3. Importantly, we detected release of human cytokines in humanized mice upon both OKT3 and TGN1412 application. Finally, humanized mice showed severe signs of illness, a rapid drop of body temperature, and succumbed to antibody application 2–6 hours after administration. Hence, the humanized mouse model used here reproduces several effects and adverse events induced in humans upon application of the therapeutic mAbs OKT3 and TGN1412.     

T cell surface antigen expression on lymphocytes of patients with AIDS during in vitro mitogen stimulation

Summary Surface marker expression on peripheral blood mononuclear cells (PBMC) was evaluated daily in PHA- and PWM-stimulated cultures of eight AIDS patients and eight normals. Before culture, the patients' cells showed the characteristic decrease in OKT 4+ cells (normals 40.4%, patients 22.3%; P<0.001), increase in OKT 8+ cells (normals 27.6%, AIDS 38.4%; P=0.002), increase in OKT 10+ cells (normals 15.5%, AIDS 42.8%; P=0.002), and increase in HLA-DR+ cells (normals 11.4%, AIDS 28.7%; P=0.01). The percentage of OKT 11+ cells remained unchanged, while the percentage of OKT 3+ cells dropped over the first 2 days in PHA but not in PWM cultures of both groups (PHA: normals 69.8% to 35.1%; P=0.001, AIDS 56.5 to 38.5%; P=0.001, PWM: normals 62.8%–65.9%, AIDS 66.8% to 63.9%), and recovered in both groups by day 5. In PWM cultures OKT 3+ cells increased significantly in normals but not in AIDS (normals 62.6%–77.7%; P=0.04, AIDS 61.8 to 48.7%). OKT 4 expression decreased in normal PHA cultures after 1 day (38.9% to 29.6%; P=0.05) and then recovered by day 5. Its expression increased in AIDS PHA cultures by day 5 (18.0%–41.1%; P<0.001). The final percentage of OKT 4+ cells in AIDS cultures was within the normal range (35.0%–49.0%). OKT 8 expression increased in both study groups after PHA stimulation (normals 29.5%–50.4%; P=0.002, AIDS 37.4%–50.7%; P=0.02) and in normals but not AIDS after PWM stimulation (normals 28.9%–35.5%; P=0.004, AIDS 38.5%–35.6%). Because of the relative changes in expression of OKT 4 and OKT 8, the 4/8 ratio declined in the normal PHA cultures (1.89 to 1.03; P=0.1) and increased in the AIDS cultures (0.68–1.18; P=0.09). Also, the sum of OKT 4+ and OKT 8+ cells in PHA cultures increased from 68% to 94% whist expression of OKT 11 remained unchanged, indicating co-expression of these antigens on individual cells. Both PHA- and PWM-stimulated normal cells showed an increase in OKT 10 (PHA 16.0%–53.4%; P=0.01, PWM 16.1%–33.9%; P=0.03) and HLA-DR (PHA 8.6%–27.3%; P=0.03, PWM 12.5%–26.6%; P=0.07). In AIDS PHA cultures this did not change, and in their PWM cultures OKT 10 expression declined (44.8 to 23.0%; P=0.05). The PHA- and PWM-stimulated cultures of AIDS patients showed a marked deficit in generation of Tac (PHA increased from 5.4% to 77.1% in normals and from 3.2% to 48.0% in AIDS; P=0.001; PWM increased from 6.1% to 35.3% in normals, and from 5.0% to 15.5% in AIDS; P=0.04). Analysis showed that this deficit was limited to a reduced expression on small lymphocytes and that those cells that did become lymphoblasts expressed Tac normally. These results indicate that the poor blastogenic responses in AIDS are related to failure of OKT 10, HLA-DR, and Tac to increase after stimulation.Abbreviations AIDS acquired immunodeficiency syndrome - PBMC peripheral blood mononuclear cells - PHA phytohemagglutinin - PWM pokeweed mitogen - Tac T cell activation antigen - ARC AIDS-related complex of symptoms - IL-2 interleukin 2 - GVHD graft-versus-host disease - HBSS Hank's balanced salt solution - RPMI 1640 Roswell Park Memorial Institute tissue culture medium 1640 - FITC fluorescein isothiocyanate     

A Biodegradable,Sustained-Released,Prednisolone Acetate Microfilm Drug Delivery System Effectively Prolongs Corneal Allograft Survival in the Rat Keratoplasty Model

Frequent and long-term use of topical corticosteroids after corneal transplantation is necessary to prevent graft rejection. However, it relies heavily on patient compliance, and sustained therapeutic drug levels are often not achieved with administration of topical eye drops. A biodegradable drug delivery system with a controlled and sustained drug release may circumvent these limitations. In this study, we investigated the efficacy of a prednisolone acetate (PA)-loaded poly (d,l-lactide-co-ε-caprolactone) (PLC) microfilm drug delivery system on promoting the survival of allogeneic grafts after penetrating keratoplasty (PK) using a rat model. The drug release profiles of the microfilms were characterized (group 1). Subsequently, forty-eight PK were performed in four experimental groups: syngeneic control grafts (group 2), allogeneic control grafts (group 3), allogeneic grafts with subconjunctivally-implanted PA microfilm (group 4), and allogeneic grafts with PA eye drops (group 5; n = 12 in each). PA-loaded microfilm achieved a sustained and steady release at a rate of 0.006–0.009 mg/day, with a consistent aqueous drug concentration of 207–209 ng/ml. The mean survival days was >28 days in group 2, 9.9±0.8 days in group 3, 26.8±2.7 days in group 4, and 26.4±3.4 days in group 5 (P = 0.023 and P = 0.027 compared with group 3). Statistically significant decrease in CD4+, CD163+, CD 25+, and CD54+ cell infiltration was observed in group 4 and group 5 compared with group 3 (P<0.001). There was no significant difference in the mean survival and immunohistochemical analysis between group 4 and group 5. These results showed that sustained PA-loaded microfilm effectively prolongs corneal allograft survival. It is as effective as conventional PA eye drops, providing a promising clinically applicable alternative for patients undergoing corneal transplantation.     

Polyclonal activation of human lymphocytes and induction of cytotoxic lymphocytes by streptococcal preparations

Polyclonal activation of human peripheral blood lymphocytes (PBLs)in vitro by preparations ofStreptococcus pyogenes Su strain (OK-432) and other heat-killed strains was investigated. The streptococcal preparations tested induce a proliferative response of PBLs via interleukin-2 (IL-2)-independent pathways. The proliferative response is accompanied by the generation of lymphoblastic cells (LBCs), which consist of heterologous lymphocyte populations: CD4⁺ helper type of T cells, and CD4^–CD8^– double-negative (DN) lymphocytes, including both CD3⁺ TcR ⁺ T cells and CD2⁺CD3^– immature type of T or non-T cell type of lymphocytes. Almost all the LBCs express Leu19, TfR (transferrin receptor), LFA-1 and CD38 (OKT10) antigens, which are expressed on activated T cells, NK cells and some other lymphocytes. The proliferative response of human PBLs is also accompanied by the generation of potent cytotoxic activity against NK-sensitive and -resistant targets. C-dependent cytolysis and cell sorting experiments of OK-432-activated LBCs revealed that both CD3⁺ and CD3^– types of CD4^–CD8^– DN lymphocytes, but not CD4⁺ helper T cells, may be major populations responsible for the cytotoxicity induced. On the other hand, CD4^–CD8 T cells may be required for the proliferation of PBLs and generation of cytotoxic effector cells. These results suggest that the OK-432 and other streptococcal preparations stimulate the human PBLsin vitro to induce the proliferation/activation of CD4⁺ T cells, mediating the following generation of DN cytotoxic effector lymphocytes.     

A DC-specific cytolytic T lymphocyte line is OKT8+1

A human cytotoxic T lymphocyte (CTL) line, A9, was generated by limiting dilution and was selected because of its apparent DC specificity. A9 is 100% OKT3+, 90% OKT4+, and 10% OKT8+, but by negative selection the CTL present are entirely OKT8+. These OKT8+ CTL are totally inhibitable by Genox 3.53, an anti-DC1 monoclonal antibody (mAb), and Leu-10, an anti-DC subgroup mAb, but are not inhibitable by a panel of anti-HLA-DR mAb. These CTL are also inhibitable by anti-OKT3 and anti-LFA-2 but not by OKT4 or OKT8 mAb. These findings extend previous studies that showed that OKT8+ CTL recognize HLA-A,B antigens, whereas OKT4+ CTL recognize HLA-DR and SB antigens. It is possible that an as yet undefined T cell surface molecule is involved in DC recognition.     

Biophysical and biochemical characterization of recombinant human Pop2 deadenylase

Pop2, a component of the Ccr4–Not complex, functions as a deadenylase both in vitro and in vivo. In this research, we found that the recombinant human Pop2 (hPop2) mainly existed in a compact monomeric state with a α + β tertiary structure type. The percentages of the secondary structures evaluated from the CD spectrum were about 37% α-helix, 14% β-sheet, and 19% β-turns. The optimal condition for hPop2 catalysis was pH 7–8 at 37 °C. Mg²⁺, Mn²⁺, and Co²⁺ had similar effects on the deadenylation activity of hPop2, and the optimal concentration was 0.3–0.5 mM. The deadenylase activity of hPop2 was, at least partially, specific when coordinated with divalent metal ions. The enzyme was not inhibited much by the nucleotide analogs, and the product 5′-AMP was the most efficient inhibitor. The dissimilarity in the metal ion dependence and inhibitory effects of the nucleotide analogs suggested that various deadenylases might have differential regulation mechanisms.     

Inhibition of β-Amyloid-Induced Neurotoxicity by Imidazopyridoindoles Derived from a Synthetic Combinatorial Library

Alzheimer's disease is a progressive neurodegenerative disorder characterized by the deposit of amyloid fibrils in the brain that result from the self-aggregative polymerization of the β-amyloid peptide (Aβ). Evidence of a direct correlation between the ability of Aβ to form stable aggregates in aqueous solution and its neurotoxicity has been reported. The cytotoxic effects of Aβ have been attributed to the aggregation properties of a domain corresponding to the peptide fragment Aβ25–35. In an effort to generate novel inhibitors of Aβ neurotoxicity and/or aggregation, a mixture-based synthetic combinatorial library composed of 23 375 imidazopyridoindoles was generated and screened for inhibition of Aβ25–35 neurotoxicity toward the rat pheochromocytoma PC-12 cell line. The effect of the identified lead compounds on Aβ25–35 aggregation was then evaluated by means of circular dichroism (CD) and thioflavin-T fluorescence spectroscopy. Their activity against Aβ1–42 neurotoxicity toward the PC-12 cell line was also determined. The most active imidazopyridoindoles inhibited both Aβ25–35 and Aβ1–42 neurotoxicity in the low- to mid-micromolar range. Furthermore, inhibition of the random coil to β-sheet transition and self-aggregation of Aβ25–35 was observed by CD and fluorescence spectroscopy, supporting the relationship between inhibition of the Aβ aggregation process and neurotoxicity.     

Th1/Th2 cytokines and ICAM-1 levels post-liver transplant do not predict early rejection

Th1 derived cytokines IFN-gamma and IL-2, Th2 cytokine IL-4, and ICAM-1 have been implicated in liver allograft rejection. In order to determine whether monitoring of cytokine profiles during the first days post-liver transplant can predict early rejection we measured IFN-gg, IL-2, sIL-2 receptor, IL-4 and ICAM-1 in 22 patients, in plasma samples obtained within 4 h after liver perfusion (baseline) and between postoperative days (POD) 3-6. ICAM-1 and sIL-2R levels at POD 3-6 were significantly higher than at baseline but did not differ in presence or absence of rejection. Mean percentage increase of ICAM-1 levels was significantly lower in patients with Muromonab-C3 Orthoclone OKT3 (J.C. Health Care) (OKT3) whereas percentage increase of sIL-2R levels was higher in OKT3-treated patients. IFN-gamma levels at POD 3-6 increased from baseline while IL-4 levels were unchanged. Levels of IFN-gamma, IL-4 and their ratios did not correlate with rejection or immunosuppressive therapy. Thus, Th1/Th2 cytokine monitoring during the first week post-transplant does not predict early rejection and immunosuppressive therapy is the predominant factor affecting ICAM and sIL-2R levels after liver transplantation.     

Characterization of interleukin-2-initiated versus OKT3-initiated human tumor-infiltrating lymphocytes from glioblastoma multiforme: Growth characteristics,cytolytic activity,and cell phenotype

Summary Outgrowth of tumor-infiltrating lymphocytes (TIL) from the human primary brain tumor glioblastoma multiforme was achieved by OKT3 initiation (10 ng/ml), followed by sustained expansion by interleukin-2 (IL-2; 200 U/ml). Tumor-infiltrating lymphocyte (TIL) initiation by this process was performed in parallel with the standard IL-2-only method. Of ten tumors, seven yielded TIL in response to OKT3/IL-2, whereas only three of these seven grew after initiation with IL-2 alone. On the basis of cell doubling times, at least 60 doublings, resulting in (hypothetically) up to 10²³ TIL from as few as 2 × 10⁵ cells in tumor suspensions, could be achieved using OKT3/IL-2. OKT3-initiated TIL proliferated in culture for as long as 288 days, although senescence of some cultures occurred at as early as 73 days. Significant heterogeneity of lymphocytes infiltrating the fresh tumors and heterogeneity of resultant TIL phenotype and function were apparent, yet several common trends were noted. In all cases after OKT3 initiation, significant net growth was not apparent until approximately 14 days. In contrast, in the three samples that grew in response to IL-2 alone, log-phase growth was always observed earlier. During the early phase of the cultures, all TIL expressed some killing activity toward a broad spectrum of tumors, including the autologous tumor. No consistent preference of TIL for lysis of autologous tumor was observed. Glioblastoma multiforme TIL cultures contained a mixture of CD8⁺ and CD4⁺ cells, with few CD16⁺ or NKH-1⁺. Of the six TIL examined in detail for population phenotype in relationship to time in culture, four eventually became exclusively CD4⁺. Further analysis of these CD4⁺ TIL indicated that all were of the helper-inducer class, 4B4⁺ and 2H4^–. Concurrent with the decline in CD8⁺ cells, a decline in the cytolytic activity of these TIL cultures occurred. Furthermore, in two TIL that remained CD8⁺, a decline in the cytolytic activity also occurred. Therefore, loss of killing activity was not merely a reflection of the major cell phenotype changes. These results indicate that the OKT3/IL-2 process provides an alternative to IL-2 alone for TIL initiation and growth, as well as providing a novel system for further analysis of tumorderived lymphocyte and accessory cell functional potential.This work was supported by a grant from the Dunn Foundation, Houston, Texas     

CD49f Is an Efficient Marker of Monolayer- and Spheroid Colony-Forming Cells of the Benign and Malignant Human Prostate

Stem cells may play a role in the development and maintenance of proliferative diseases of the prostate such as prostate cancer and benign prostatic hyperplasia. Cell membrane protein markers, CD49f, CD133 and CD44, have been shown to identify putative prostate stem cells, but a lack of consensus exists with regards to the most efficient marker(s) for stem-like cell identification. This study aimed to determine whether previously reported markers had equal capacity to select monolayer and spheroid colony-forming cells (CFCs), which were used as surrogate readouts of stem-like cells, and to characterize the expression of CD49f, CD44 and CD133 by flow cytometry and immunohistochemistry.In benign prostate cells, CD49f+, CD44+, and CD133+ cells represented 5.6±3.1%, 28.2±4.1% and 0.10±0.06% of total cells. Both monolayer- and spheroid-CFCs existed at a frequency of approximately 0.5% of total cells. CD49f+, CD44+, and CD133+ subpopulations differed significantly in their ability to select benign CFCs. The highest recovery of CFCs was achieved by CD49f+ selection (98%), whereas CD44+ or CD133+ selection led to poor CFC-recovery (17% and 3%, respectively). For the first time, we show highly efficient recovery of CFCs from advanced prostate cancer by CD49f+, but not by CD44+ or CD133+ selection. Furthermore, CD133 expression (AC133 clone) could not be detected in benign prostate cells by either immunohistochemistry or flow cytometry. We conclude that CD49f, but not previously described stem cell markers CD133 and CD44, to be optimal for selection of monolayer- and spheroid-CFCs in the benign and malignant prostate.     

Spontaneous human T-cell cytotoxicity against murine hybridomas expressing the OKT3 monoclonal antibody: comparison with natural killer cell activity

Human peripheral blood lymphocytes (PBL) exhibited spontaneous cytotoxicity against OKT3 monoclonal antibody (mAb)-expressing murine hybridoma cells (OKT3 hybridomas). In contrast, other murine hybridomas expressing OKT4, OKT8, anti-HLA DR, and anti-HLA A, B, and C mAb were not lysed. PBL showed much lower levels of cytotoxicity (3 folds) against OKT3 hybridomas as compared with NK activity against the K562 targets. Lymph node (LN) cells exhibited the inverse relationship of cytotoxicity levels. The addition of OKT3 mAb to the effector cells totally blocked both the binding and the lysis of OKT3 hybridoma targets, indicating that the CD3 antigen on the effector cells may be involved in recognition of the targets. The addition of concanavalin (Con A) also inhibited the cytotoxicity of OKT3 hybridomas. OKT4 mAb-expressing hybridomas became susceptible to lysis after chemical attachment of OKT3 mAb with CrCl3. The kinetics of lysis of OKT3 hybridomas resembled that of NK activity. Both cytotoxicities were detectable after 1 to 2 hr and reached plateau levels by 4 to 6 hr. Effector cells responsible for lysis of OKT3 hybridomas expressed T3, T8, and Leu 7 antigens, but lacked T4 and Leu 11b antigens, and were sensitive to the treatment with L-leucine methyl ester. These results indicate that T3+, T8+, Leu 7+ and T4-, and Leu 11- granular lymphocytes have a spontaneous cytotoxic activity against OKT3 hybridomas which is different from classic NK activity. These findings may provide a method for the assessment of T-cell cytotoxicity mediated presumably by in vivo generated cytotoxic T lymphocytes in blood and the other immune organs.     

Agar human T cell colony growth promoted by a B + null cell-derived lymphokine distinct from IL 2

Human T cell agar colonies can be grown under PHA stimulation from either mature T cells or their E rosette-negative (E-), OKT3- peripheral blood and bone marrow precursors. Colonies comprise a majority of mature E+, OKT3+ cells and a minor (5 to 10%) population of immature E-, T3-, T8-, T4-, DR+, T10+, RFB1+ cells, which upon replating in subculture, can generate secondary colonies of OKT3+, E+, OKT4+, OKT8+ cells. Secondary colony formation can serve as a test for growth requirement of colony precursors, because it depends on the presence of both PHA and a colony-promoting activity (CPA) recovered in PHA-stimulated B + null or T + adherent cell supernatants. CPA production by B + null cells was not affected by their treatment with OKT3 or D66 (T11-like) monoclonal antibodies (MAB) + complement but was abolished by an anti-HLA-DR MAB + complement. However, B cells sorted by panning with the same anti-HLA-DR MAB did not release CPA, demonstrating the requirement of both B cells and null cells for CPA production. Neither IL 2 nor IL 1 could account for B + null cell-derived CPA.     

<Emphasis Type="BoldItalic">Phellinus linteus</Emphasis> grown on germinated brown rice suppresses IgE production by the modulation of Th1/Th2 balance in murine mesenteric lymph node lymphocytes

We compared the immunomodulating effects of Phellinus linteus (PL), germinated brown rice (BR) and P.␣linteus grown on germinated brown rice (PB) on IgE production in murine mesenteric lymph node (MLN) lymphocytes. All extracts decreased IgE concentrations by 43–65% compared to control mice in both serum and MLN lymphocytes. In addition, PL and PB increased the proportion of CD4⁺ T cells by␣9% and 12% in MLN lymphocytes. IFN-γ concentration, Th1 cytokine, was significantly increased by 44–67%, whereas IL-4 and IL-10 concentrations, Th2 cytokine, significantly decreased by 30–60% in the three treated groups compared to control group. These results suggest that PB suppresses IgE production through the modulation of Th1/Th2 balance to down-regulate Th2 response in MLN lymphocytes, even though a synergistic effect of PB was not found.     

CD4+ and CD8+ T Cells Can Act Separately in Tumour Rejection after Immunization with Murine Pneumotropic Virus Chimeric Her2/neu Virus-Like Particles

Background

Immunization with murine pneumotropic virus virus-like particles carrying Her2/neu (Her2MPtVLPs) prevents tumour outgrowth in mice when given prophylactically, and therapeutically if combined with the adjuvant CpG. We investigated which components of the immune system are involved in tumour rejection, and whether long-term immunological memory can be obtained.

Methodology and Results

During the effector phase in BALB/c mice, only depletion of CD4⁺ and CD8⁺ in combination, with or without NK cells, completely abrogated tumour protection. Depletion of single CD4⁺, CD8⁺ or NK cell populations only had minor effects. During the immunization/induction phase, combined depletion of CD4⁺ and CD8⁺ cells abolished protection, while depletion of each individual subset had no or negligible effect. When tumour rejection was studied in knock-out mice with a C57Bl/6 background, protection was lost in CD4^−/−CD8^−/− and CD4^−/−, but not in CD8^−/− mice. In contrast, when normal C57Bl/6 mice were depleted of different cell types, protection was lost irrespective of whether only CD4⁺, only CD8⁺, or CD4⁺ and CD8⁺ cells in combination were eradicated. No anti-Her2/neu antibodies were detected but a Her2/neu-specific IFNγ response was seen. Studies of long-term memory showed that BALB/c mice could be protected against tumour development when immunized together with CpG as long as ten weeks before challenge.

Conclusion

Her2MPtVLP immunization is efficient in stimulating several compartments of the immune system, and induces an efficient immune response including long-term memory. In addition, when depleting mice of isolated cellular compartments, tumour protection is not as efficiently abolished as when depleting several immune compartments together.     

Preparation and analysis of bifunctional immunoconjugates containing monoclonal antibodies OKT3 and BABR1

Summary OKT3 and BABR1 [anti-(breast tumour) antibody] were conjugated usingN-succinimidyl-3-(2-pyridyldithio)propionate (SPDP). The procedure employed mild reducing conditions for SPDP-BABR1 and short conjugation incubations at 37°C. The bifunctional immunoconjugates thus produced were isolated by HPLC gel filtration on a preparative TSK 3000 SW column. Both intact IgG and F(ab)₂ fragments have been conjugated. The ratio of SPDP to IgG for the optimal yield of dimeric OKT3-BABR1 heteroconjugates was determined to be 2 for OKT3 and 1–2 for BABR1. The OKT3-BABR1 dimers were shown to be bifunctional heteroconjugates by polyacrylamide gel electrophoresis, isoelectric focusing, radial immunodiffusion, and flow cytometry. The binding specificities of the bifunctional heteroconjugates were identical to the specificities of both parent antibodies.     

Evidence for differentiation of NK1+ cells into cytotoxic T cells during acute rejection of allogeneic bone marrow grafts

The ability of lethally irradiated C57BL/6 mice to acutely reject H-2^d bone marrow is due to a lymphocyte population that is NK1⁺, ASGM1⁺, CD4^–, CD8^–, CD3⁺. Transfer of spleen cells from C57BL/6 mice expressing these antigens into nonresponder 129 mice adoptively transfers the ability to reject H-2^d marrow grafts. The specificity of this rejection maps to the H-2D major histocompatibility complex (MHC) region. Transplantation of high doses of H-2^d marrow into C57BL/6 overrides the acute rejection mechanism leading to graft survival. During growth of the graft, a cytolytic activity develops that is due to ASGM1⁺, CD8⁺ cytolytic T lymphocytes (CTLs) with H-2L^d specificity. The possibility that the ASGM1⁺, CD8⁺ CTLs are descendents of the CD3⁺, NK1⁺, ASGM1⁺, CD8^– cells responsible for acute rejection is investigated by adoptive cell transfer experiments. We show that beige mice that lack NK1⁺ cells as well as the ability to acutely reject H-2^d marrow fail to generate specific CTLs after transplantation with a high dose of H-2^d marrow. Transfer of highly purified NK1⁺ cells from B6.PL-Ly-2 ^a /Ly-3 ^a (Lyt-2.1) into beige mice together with H-2^d marrow leads to generation of Lyt-2.1 CTLs from donor NK1⁺ cells. These results show that specific CTLs are generated from NK1⁺ cells during acute marrow graft rejection. Offprint requests to: G. Dennert.     

Structural basis of cell–cell interactions in the immune system

During the past year, advances in our understanding of receptor–ligand interactions between opposing cell surfaces have occurred at a structural level. These include adhesion involving CD2–CD58, antigen-specific T-cell receptor interactions with peptides bound to major histocompatibility complex molecules (both pMHCI and pMHCII), the CD8αα co-receptor–pMHCI interaction and the binding of two distinct classes of natural killer receptors to self-MHC ligands.