anti-T Cell Antibodies Research Articles

Induction of tolerance to heart allografts in rats using posttransplant total lymphoid irradiation and anti-T cell antibodies.

This study examined whether posttransplant anti-T cell monoclonal or polyclonal antibody therapy could provide a window of treatment to allow posttransplant total lymphoid irradiation (TLI) to induce tolerance. These experiments were conducted in a high responder strain combination of an ACI cardiac allograft into a Lewis rat. In this situation, treatment with antibody or posttransplant TLI alone is insufficient to induce tolerance, while similar treatments alone have been shown to induce tolerance in low responder strains. The affects of three anti-T cell therapies were compared: anti-CD4 mAb therapy, anti-CD3 mAb, and rabbit antithymocyte globulin (RATG). None of these antibody therapies alone prolonged graft survival indefinitely. Combining anti-CD4 therapy with posttransplant TLI markedly delayed rejection but failed to induce long-term graft survival. Tolerance could be induced by a combination of anti-pan T cell antibody (anti-CD3) and TLI, and, all grafts survived beyond 100 days. RATG failed to prevent graft rejection when used alone or in combination with TLI. However, posttransplant therapy with a combination of RATG, TLI, and single-donor blood transfusion resulted in graft survival beyond 100 days. Recipients bearing long-term donor grafts rejected third-party (PVG) grafts within 2 weeks. Low density donor bone marrow cells used instead of a blood transfusion did not facilitate tolerance. The results indicate that monoclonal or polyclonal anti-pan T cell antibodies, TLI, and a donor blood cell infusion function synergistically in facilitating tolerance to allografts in the posttransplant period.

Cloned human CD4+ cytotoxic T lymphocytes specific for Toxoplasma gondii lyse tachyzoite-infected target cells.

Infection with Toxoplasma gondii is an important cause of morbidity and mortality throughout the world. In immunocompetent hosts, the infection is usually not significant. However, infection occurring in neonates or other individuals with defective cellular immunity (such as recipients of organ allografts or persons with AIDS) may be life threatening. An effective vaccine to prevent toxoplasmosis, or immunotherapy for persons already infected with Tg would be important additions to the therapeutic armamentarium. We cloned toxoplasma-specific CTL from the PBMC of an asymptomatic individual with serologic evidence for prior Tg infection by stimulation with Ag produced from the RH strain of Tg. These CTL were exclusively of the CD3+, CD4+, CD8- surface phenotype, and lysed autologous target cells that had been either pulsed with Toxoplasma Ag, or infected with live tachyzoites. Lysis of target cells was inhibited by incubation of CTL with anti-T cell antibody, or by incubation of target cells with anti-DR antibody or chloroquine. These CTL also lysed target cells either pulsed with Ag derived from C strain Tg or infected with live C strain tachyzoites, indicating cross-reactivity of recognition. Unlike recently reported murine or human CD8+ Tg-specific CTL, which lysed tachyzoites in an extracellular, and hence HLA-unrestricted environment, these CD4+ CTL had no effect on the infectivity of extracellular tachyzoites. CD8+ Tg-specific CTL were not derived from this donor despite several different approaches to their generation. These data confirm previous reports of human Tg-specific CTL, and extend these observations to include CD4+ CTL. These findings suggest that specific immunotherapy directed against Tg, as well as the development of a preventive vaccine, may be possible.

Intrathymic and Extrathymic Tolerance in Bone Marrow Chimeras

Parent-->F1 bone marrow (BM) chimeras provide a useful model for studying self tolerance induction. When prepared with supralethal irradiation (1300 cGy) and conditioned with anti-T cell antibodies, parent-->F1 BM chimeras are devoid of host BM-derived cells; host H-2 expression is apparent in both the intrathymic and extrathymic environments but is limited to non BM-derived cells. When parent-->F1 chimeras are injected with T cells from normal parental strain mice, the expression of host H-2 antigens on nonprofessional APC might be expected to induce tolerance through induction of clonal anergy. In practice, this does not occur. Instead, a small proportion of the injected T cells is induced to proliferate and differentiate into effector cells. Tolerance is not seen. Similarly, tolerance is not apparent when thymectomized parent-->F1 chimeras are given parental strain thymus grafts. These findings suggest that the expression of host H-2 antigens in the post-thymic environment of chimeras is not intrinsically tolerogenic for mature T cells or recent thymic emigrants. Interestingly, post-thymic tolerance does occur when parental strain T cells differentiate in the endogenous thymus of chimeras. Thus, when mature CD8+ cells are prepared from thymus vs lymph nodes (LN) of parent-->F1 chimeras, tolerance to host class I antigens is more marked in LN than thymus; this applies to cytotoxic T lymphocyte (CTL) precursors, generated by limiting dilution analysis. It would appear therefore that many of the host-reactive CTL precursors generated in the thymus of chimeras undergo tolerance induction (deletion or irreversible inactivation) in the post-thymic environment. We suggest that such tolerance is a reflection of a covert form of tolerance induced in the thymus: intrathymic contact with host antigens on thymic epithelial cells (TEC) in chimeras does not delete typical CTL precursors, but these cells are rendered "semi-tolerant". When cultured in vitro in the presence of lymphokines, the cells are able to recover and differentiate into CTL. In vivo, however, the cells recognize antigen in the periphery in the relative absence of lymphokines and the cells die. Although host class I expression on TEC in chimeras deletes only a small proportion of CTL precursors, contact with TEC induces strong tolerance of CD8+ cells in terms of helper-independent proliferative responses in vitro and induction of lethal graft-versus-host disease in vivo. We postulate that these latter responses are controlled by high-affinity T cells, whereas typical CTL generated in LDA are predominantly low-affinity cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Failure to demonstrate suppressor T cell activity in the lamina propria of Hymenolepis diminuta-infected rats.

The aim of this study was to examine whether there was an increase of suppressor T cells, relative to helper T cells, in the intestinal lamina propria of Hymenolepis diminuta-infected rats, a condition which might allow the parasite to survive for the life-span of the host. Lamina propria cells were isolated by enzymatic procedure. All lymphocytes were passed over nylon wool columns in order to remove B cells; then the T cells were purified by a panning technique using monoclonal anti-T cell antibodies. Changes in the mitogen-stimulated synthesis of IgM, IgG and IgA by normal peripheral blood indicator lymphocytes, as measured by sandwich ELISA, was used as an index of help and/or suppression. No significant suppressor T cell activity was observed in the cultures, either from control or infected intestine.

Changes in subset specificity of anti-T cell autoantibodies in systemic lupus erythematosus.

Relative reactivity of anti-lymphocyte autoantibodies (ALA) from patients with systemic lupus erythematosus (SLE) against CD4+ and CD8+ T cells was studied using C-dependent microcytotoxicity assay. Of 46 SLE sera screened for anti-T cell autoantibodies, 27 sera (59%) showed significant cytotoxic reactivity. Of these, positive correlation between the titer of anti-T cell antibody and CD4/CD8 killing ratio (p < 0.01) was demonstrated. In time course study of individual patients, the CD4/CD8 killing ratio increased and decreased as the disease flared and subsided and was accompanied by parallel changes in the titer of anti-T cell antibody titer. Moreover, as sera were serially diluted, the CD4/CD8 killing ratio decreased in 5 out of 10 sera. These results suggest that discrepancy among reports concerning the subset specificity of anti-T cell antibodies may be due, in part, to differences in the titer of ALA in the sera studied and to the dilution of serum used.

Patent Evaluation: Autoantibodies to CD43 as a Target for HIV Diagnosis

SummaryNovelty: A novel AIDS therapy using a CD43 antigen is disclosed. Useful CD43 antigens include a CD43 fragment capable of binding to an anti-CD43 autoantibody observed in HIV-1 infected people. The fragment is sufficiently large to efficiently bind anti-CD43 autoantibodies produced by the patient, thereby preventing the antibodies from binding to CD43+ lymphocytes. A method for detecting the presence or progress of HIV-1 infection by determining whether autoantibodies (i.e. anti-CD43 autoantibodies) are present also is discussed. A further method detects anti-T cell antibodies (i.e. anti-CD43 antibodies).Biology: The amount of soluble CD43 required for therapy is between 10 μg/kg bodyweight and 500 μg/kg body weight per day. The presence of surface Ig+ T cells is shown to be indicative of HIV infection, in that none of the forty-four seronegative individuals tested contained such cells in their blood.

Regulation of tumor necrosis factor production by monocyte-macrophages and lymphocytes

TNF, a cytokine originally considered the product of only one cell type, the monocyte-macrophages, is now known to be produced by cells of many different lineages, with mechanisms of stimulation typical for each cell type analyzed. The fact that many different cell types can produce a cytokine such as TNF that has a very large spectrum of biologic functions on almost any target cell type is suprising. The functions of the cell types that produce TNF, e.g. monocyte-macrophages, neutrophils, T and B cells, are profoundly affected by TNF itself. Furthermore, TNF is able to induce its own gene, making these autocrine circuits even more complex. Because TNF has important systemic effects and it has been shown to be in vivo a major and necessary pathogenetic factor in situations such as endotoxin shock, graft-versus-host disease, and hypothermia induced by anti-T cell antibodies, it is clear that its production and its localization should be highly regulated in vivo and that our understanding of the regulation of TNF production based almost exclusively on in vitro observation is still very limited. Further analysis of the fine mechanisms of regulation of TNF production in vivo is required for a better under standing of the role of TNF in physiological and pathological conditions.

Monoclonal anti-T cell (T12) antibody treatment of graft-versus-host disease in severe combined immunodeficiency: targeting of antibody and activation of complement on CD8 + cytotoxic T cell surfaces

We report a 6-month-old male child with severe combined immunodeficiency who received an unirradiated blood transfusion and developed acute, severe graft-versus-host disease (GVHD), for which he received monoclonal anti-T cell (anti-T12) antibody treatment. The GVHD was manifested by a confluent maculopapular rash and increased liver function tests and was documented by skin biopsy. Separation of peripheral blood mononuclear cells forming rosettes with sheep red blood cells revealed engrafted T cells having the nonrelated HLA type of the blood donor. The patient was treated with intravenous monoclonal anti-T12 in a dose of 0.3 mg/kg/day for 5 days. An in vivo effect of the anti-T12 was suggested by clinical improvement of his skin rash and return of the liver transaminases to the normal range. Moreover, human complement components, activated C3 and C4, were detected by fluorescence microscopy on the surfaces of the engrafted CD8 + lymphocytes on the skin biopsy specimens. Also, with a biotin-avadin assay, the presence of the anti-T12 was detected on these same cells. These studies document not only the in vivo targeting of monoclonal anti-T12 antibody to cytotoxic T cells producing GVHD but also the activation of complement on these cells.

Infection of human thymocytes by Epstein-Barr virus.

The Epstein-Barr Virus (EBV) causes infectious mononucleosis, and has been strongly associated with certain human cancers. The virus is thought to exclusively bind to B lymphocytes and epithelial cells via receptors (CR2/CD21) that also interact with fragments of the third component of complement (C3). Recent evidence, however, has challenged this belief. We have used two-color immunofluorescence analysis using biotin-conjugated EBV and streptavidin-phycoerythrin along with fluorescein-conjugated anti-T cell antibodies and demonstrated that CD1-positive, CD3-dull (immature) human thymocytes express functional EBV receptors. In four replicate experiments, the binding of EBV to thymocytes ranged between 8 and 18%. This interaction is specific as evidenced by inhibition with nonconjugated virus, anti-CR2 antibodies, aggregated C3, and an antibody to the gp350 viral glycoprotein that the virus uses to bind to CR2. EBV can infect the thymocytes as evaluated by the presence of episomal EBV-DNA in thymocytes that had been incubated with the virus as short as 12 days or as long as 6 weeks. Episomal DNA analysis was performed by Southern blotting with a EBV-DNA probe that hybridizes to the first internal reiteration of the viral DNA. The presence of the EBV genome is also supported by the detection of EBV nuclear antigen 1 in infected thymocytes, assessed by Western blotting with EBV-immune sera. The EBV infection is specific as determined by blocking experiments using anti-CR2 and anti-gp350 antibodies. Finally, virus infection of thymocytes can act synergistically along with interleukin 2 and induce a lymphokine-dependent cellular proliferation. In view of previously reported cases of EBV-positive human T cell lymphomas, the possibility is raised that EBV may be involved in cancers of T lymphocytes that have not been previously appreciated.

Screening for growth hormone gene deletions in patients with isolated growth hormone deficiency

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Microvascular Architecture of Rat Nasal Associated Lymphoid Tissue.

The blood vascular architecture of the rat nasal associated lymphoid tissue (NALT) was studied by scanning electron microscopy of corrosion casts. To examine the correlation of the vasculature with the distribution of lymphocyte subsets, the NALT was also studied by light microscopy of immuno-stained samples. The NALT was supplied by a branch of the inferior nasal artery which arose from the sphenopalatine artery. This branch reached the bottom of the NALT and ramified arterioles to the follicles and the parafollicular regions. These arterioles ascended toward the subepithelial region, giving off capillaries en route to form a coarse plexus within the follicles and the parafollicular regions. The arterioles reached the subepithelial region and formed a subepithelial capillary network consisting of a single layer of flat meshwork. The follicular, parafollicular and subepithelial capillaries anastomosed one another. The capillaries in each region were gathered into collecting venules, which in turn drained into high endothelial venules (HEVs) in the parafollicular region. The HEVs ran through the parafollicular regions around the follicular perimeters, and flowed into ordinary veins to leave the NALT. Lymphocytes labeled with an anti-T cell antibody were mainly distributed in the parafollicular regions, where HEVs were situated. B cells were mostly observed in the follicular and dome areas. The microvascular structure and its correlation with lymphocyte subset domains in the NALT were essentially similar to those in other mucosa associated lymphoid tissues (MALTs) such as tonsils and Peyer's patches.

The role of OKT3 in clinical transplantation

OKT3 is a murine monoclonal anti-T cell antibody that is directed to CD3, a five-chain molecular complex found in association with the T cell receptor for antigen. OKT3 was the first monoclonal antibody to be used in organ transplantation and during the past 10 years there has been extensive experience of its use both for preventing and treating rejection in organ transplantation. OKT3 blocks T cell function by modulating CD3 and the T cell receptor from the T cell surface. A reaction to OKT3 results from cytokines released when OKT3 first reacts with T cells. This reaction is generally mild but can be severe. First rejections following kidney transplantation are reversed in approximately 95% of cases. Steroid-resistant rejections are also susceptible to OKT3 but in only approximately 75% of cases. When used for prophylaxis, OKT3 completely blocks rejection in 95% of patients and significantly delays the onset of rejection in those who do reject. Antibodies to OKT3 are produced in approximately 75% of patients receiving it. However, seldom are the antibodies to OKT3 present in high titer and only in those cases is successful re-use of OKT3 prevented. As is the case with all potent immunosuppressive drugs, the use of OKT3 is associated with increased viral, specifically cytomegalovirus, infections. However, it appears that reduction of concomitant immunosuppression decreases the incidence of severe infections. Unquestionably, OKT3 has been a useful addition to the immunosuppression used for organ transplantation. In addition, its use has stimulated research on other monoclonal antibodies for use in organ transplantation.

HEPATOCYTE TRANSPLANTATION FOR THE LOW-DENSITY LIPOPROTEIN RECEPTOR-DEFICIENT STATEA

The Watanabe heritable hyperlipidemic (WHHL) rabbit reproduces human familial hypercholesterolemia due to a congenital low-density lipoprotein receptor deficiency and is characterized by elevated serum LDL cholesterol levels and early atherosclerosis. We attempted to transplant normal allogeneic hepatocytes into WHHL rabbits without chronic immunosuppression to cure the LDL receptor-deficient state. Livers from normal New Zealand White (NZW) rabbits were digested by intraportal perfusion of collagenase solution. Pure hepatocytes (PH) were obtained by Percoll gradient separation and nonparenchymal (NP) liver cells by pronase digestion. PH and NP were incubated with fluorescein isothiocyanate-monoclonal anti-rabbit class I, anti-class II, and anti-T cell antibodies and subjected to flow cytometry analysis. PH and NP were also used as stimulators in one way mixed lymphocyte-hepatocyte cultures (MLHC), before and after ultraviolet B light (UVB) exposure. Intraportal and intrasplenic injection of allogeneic PH were also performed in homozygous WHHL rabbits. PH were attached to collagen-coated dextran microcarriers (mc-PH) for intraperitoneal injection. Recipient control and transplanted WHHL rabbits received a single dose of cyclosporine subcutaneously (10 mg/kg/s.c.) at the time of transplantation. PH were mainly class I-positive (77.6%) and class II-negative (5.9%), while 31.5% of NP cells were class II-positive. In MLHC, PH did not stimulate proliferation, (stimulation index: 0.97 +/- 0.21), unlike NP (SI: 23.7). This latter response was abrogated by prior exposure of NP to UVB light. Intraportal injection of PH (n = 4) reduced serum LDL cholesterol to 60% of baseline, an effect lasting 2-3 weeks, and dose-dependent. Intraperitoneal mc-PH, 4 x 10(8) (n = 4), reduced serum LDL cholesterol levels to 45% of baseline more than 4 weeks posttransplant (P = 0.04). We conclude that transplantation of normal allogeneic NZW rabbit mc-PH reduces serum LDL cholesterol levels in homozygous WHHL rabbits without chronic immunosuppression. Longitudinal studies will establish if less atherosclerosis develops in mc-PH WHHL recipients than sham controls.

The effects of anti-CD4 and anti-CD8 antibody treatment on placental growth and function in allogeneic and syngeneic murine pregnancy

During pregnancy, maternal immune recognition of paternal alloantigens has been shown to result in an increased influx of maternal T cells into the spleen, draining lymph nodes and decidua. In previous studies we have shown that polyclonal or monoclonal anti-T cell antibody treatment of allogeneically pregnant mice results in decreased placental proliferation and phagocytosis in vivo. In the present study we compare the effect of such antibody treatment during allogeneic and syngeneic pregnancy. We show that monoclonal anti-CD8 treatment of both types of pregnant females reduces placental proliferation and phagocytosis. Anti-CD4 antibody treatment, on the other hand, only affects placental proliferation, indicating that there is a complex network of immune interactions affecting placental growth and function.

Proteoglycan‐induced polyarthritis and spondylitis adoptively transferred to naive (nonimmunized) BALB/c mice

Mononuclear cells from BALB/c mice with progressive polyarthritis and spondylitis induced by injection of fetal human articular cartilage proteoglycan (PG) were used to transfer arthritis by intravenous injection into irradiated, nonimmunized syngeneic mice. Successful transfer of arthritis to BALB/c mice required the injection of lymphocytes from mice with arthritis, along with 50 micrograms of human fetal PG, or lymphocytes stimulated in vitro with either fetal human PG or with mouse cartilage PG. In addition, interleukin-2 or immune sera from animals with arthritis significantly reduced the time to onset of transferred disease. The onset of adoptively transferred arthritis, using cells and antigen, from the time of the first injection (38.2 +/- 18.2 days, mean +/- SD) was shortened if lymphocytes from mice with transferred arthritis were reinjected (retransferred) into other, irradiated syngeneic mice (6.1 +/- 2.6 days). The appearance of autoreactive antibodies to mouse cartilage PG in the sera of mice with adoptively transferred arthritis (secondary or tertiary) preceded the appearance of the first clinical symptoms by a few days. The transfer of arthritis was blocked by pretreatment of donor (arthritic) lymphocytes with either anti-T cell or anti-B cell antibodies and complement. Exposure of mononuclear cells from mice with arthritis to PG, and its removal prior to transfer, also resulted in transfer of the arthritis. PG-induced arthritis was not transferred to nonirradiated mice, nor to irradiated mice injected with lymphocytes from animals with primary arthritis without chondroitinase ABC-digested fetal human PG. Arthritis never developed after injection of immune sera from mice with arthritis (without cells), nor when cells of nonarthritic animals were used with chondroitinase ABC-digested fetal human PG, with or without interleukin-2.

Immunohistologic study of mononuclear cell infiltrates in oral squamous cell carcinomas

Intensity of mononuclear cell infiltrates in 50 oral cancer tissues was evaluated by immunohistochemical stainings. The intensity of the infiltrates was graded into four degrees from marked ( ) to absent (-); and the degree of each infiltrated lymphocyte subpopulation including Leu-3a3b/Leu-2a ratio was matched against clinical and histopathologic features. The vast majority of the infiltrated lymphocytes had antigens which were reactive with anti-T cell antibodies. In T cell subsets, Leu-3a3b+ cells infiltrated clearly (grade ++ or ) in 44 cases, and infiltration greater than grade ++ of Leu-2a+ cells was found in nearly half of the cases (26 of 50). In contrast, B cells (Leu-14+ cells) were obviously detectable in only a few cases, and moderate or marked infiltration of the natural killer (NK) population (Leu-11b+ cells) was not observed. Regarding correlation of T cell infiltrates with clinicopathologic features of the tumors, the degrees of Leu-4+ cell and Leu-2a+ cell infiltration became weak with advancing T stage. Leu-2a+ cells also infiltrated weakly into diffusely invading tumors. Out of 28 cases with no metastasis, 22 cases (78.6%) showed grade ++ approximately of Leu-2a+ cells, and only 4 (18.2%) of 22 cases with lymph node metastasis were clearly positive for Leu-2a+ cells (p less than 0.001). However, Leu-3a3b+ cell infiltration was only slightly related to T stage, metastasis, and to mode of invasion. Therefore, the Leu-3a3b/Leu-2a ratio increased significantly in advanced (T3 + T4) tumors, metastasized cases, or diffuse invasion type.

Dichotomous effect of monocyte Fc receptor interaction on anti-CD3-induced immunoglobulin synthesis

Monoclonal antibodies against the TCR/CD3 complex are capable of activating T cells which in turn may induce immunoglobulin synthesis in B cells under appropriate conditions. Here we present evidence that distinct immune responses, induced by four commonly used TCR/CD3 mAb (Leu4, OKT3, BMA030, BMA031) were related to the mAb interaction with monocyte Fc receptors for IgG. Depending on their isotype and on the technique by which they were crosslinked, TCR/CD3 mAb induced variable IgM and IgG synthesis in PBMC: If the mAb were crosslinked by monocyte IgG-Fc receptors they induced a high Ig production, while cross-linking the same mAb by plastic-bound goat anti-mouse antibodies (panning) failed to do so. Nevertheless, both crosslinking techniques triggered a strong proliferation and IL-2, IL-4, and IFNγ lymphokine gene expression. The lack of Ig production under panning conditions was due to an additional IgG-Fc receptor interaction with monocytes: (a) If namely mAb F(ab′) 2 fragments, or mAb isotypes unable to bind to monocyte Fc receptors (IgG2b, IgG1 in nonresponders) were crosslinked by panning, both a good proliferation as well as Ig production ensued; (b) if TCR/CD3 mAb isotypes which could additionally bind to monocyte Fc receptor (IgG2a) were crosslinked, no Ig production occurred; (c) if mAb F(ab′) 2 fragments were cross-linked with a second anti-T cell antibody of IgG2a isotype, which could bind to monocyte Fc receptors, Ig synthesis was reduced. Interestingly enough, this diminishing effect, due to monocyte Fc receptor interaction, was only observed if CD4-positive cells were proliferating, but not if CD8-positive cells were activated.

Evaluation of la expression in rat ocular tissues following inoculation with interferon-gamma

It is becoming increasingly clear that IFN-gamma is a potent immunoregulatory protein which influences MHC class II (Ia) antigen expression and cellular functions of B cells, T cells, NK cells and macrophages. During the past 5 yr our laboratory has provided evidence that IFN-γ modulates class II antigens on retinal cells (retinal pigment epithelial cells, endothelial cells) and is localized within the eye during human inflammatory conditions. In this study we evaluate the direct effect of IFN-γ on ocular tissue. Lewis rats were inoculated intravitreally or under the retina with either recombinant IFN-γ (20 000 U) or saline. At 2 hr, 1, 2 and 6 days postinoculation, the eyes were removed and frozen sections were evaluated by immunocytochemical staining with monoclonal anti-la antibodies and an irrelevant monoclonal anti-T cell antibody. Saline treated tissue and tissue removed 2 hr after IFN-γ inoculation showed no significant staining for Ia antigens. However, eyes evaluated 24 hr after IFN-γ inoculation revealed Ia expression on a variety of ocular cells localized in the conjunctiva and anterior segment, such as conjunctival epithelium, keratocytes, iris epithelium, ciliary epithelium and choroidal cells. In the retina, retinal pigment epithelial (RPE) cells were Ia positive only when IFN-γ was injected directly under the retina. In conjunction with Ia expression, two striking changes were noted. An iritis was seen and infiltrating cells were detected in the inner retinal layers. Both of these phenomena have been observed in certain inflammatory eye diseases. These studies clearly substantiate the concept that IFN-γ can regulate class II antigens in the eye and thus may perpetuate immune reactivity in this site.

Dual antibody stimulation: Role of monocyte products and activation requirements of T cell subsets

Using the model of dual antibody stimulation (cross-linking anti-CD3 BMA030-F(ab′) 2 antibodies with subset specific anti-T cell antibodies, i.e., anti-CD4 or anti-CD8 antibodies) we investigated the role of monocyte products in eliciting IL2 production and asked whether T cell subsets differ in their activation requirements. We found that activation mechanisms of dual antibody stimulation were equal for CD4 and CD8 as well as CD4 CDw29 and CD4 CD45R T cell subsets: dual antibody stimulation was necessary to induce responsiveness to soluble monocyte products which trigger IL2 synthesis. IL2 production induced by soluble monocyte products was measured in CD4 and CD8 T cells as specific IL2 mRNA expression and with a biological assay. Combined actions of IL1β and TNFα were identified as active monocyte products as (a) treatment of LPS-stimulated monocyte supernatants with anti-IL1β and anti-TNFα antibodies abrogated the proliferation inducing effect of monocyte supernatants and (b) addition of rIL1β and/or rTNFα enhanced proliferation of T cells stimulated by dual antibody cross-linking. If both recombinant monokines were added simultaneously a potentiated proliferative effect was observed. Whereas rIL1β plus/or rTNFα sustained proliferation, only rIL1β but not rTNFα induced IL2 synthesis in T cell subsets stimulated by dual antibody cross-linking.

Natural killer (NK) activity and interferon (IFN) production by a fraction of spleen and blood lymphocytes in swine

After carbonyl iron treatment and gradient isolation, spleen and blood pig lymphocytes exhibited NK activity and produced IFN after viral induction. Removal of plastic-adherent cells, including the majority of B cells, did not change these activities. The plastic-non-adherent cells were further separated into two subsets of roughly similar size by panning using a monoclonal, anti-T, and anti-null cell antibodies (81+cells). NK activity and IFN production were found in the 81 − cell fraction. A significantly higher proportion of null lymphocytes from blood and of splenic Fc-gamma receptor-bearing lymphocytes was also found among the 81 − cell fraction as compared to the 81 + fraction, without any change among other subsets. Similar proportions of helper (PT4+), cytotoxic (PT8+) and total T cells (MSA4+) were found among lymphocytes bound to target K562 cells and among the whole lymphocyte population. In contrast, lymphocytes that bound K562 cells demonstrated a striking increase in the proportion of Fc-gamma receptor-positive cells of high affinity. These results show that NK cells and IFN-producing cells are mainly included in the same blood and spleen fraction, and suggest that among 81 − cells only those expressing an Fc-gamma receptor of high affinity are active.