Localization of human antigen-specific helper and suppressor function in distinct T-cell subpopulations

Oxidative stress decreases G protein-coupled receptor kinase 2 in lymphocytes via a calpain-dependent mechanism

G protein-coupled receptor kinase (GRK) 2 plays a crucial role in regulating the extent of desensitization and resensitization of G protein-coupled receptors (GPCRs). We have shown that the expression level of GRK2 in lymphocytes decreases during inflammatory diseases such as arthritis. Reactive oxygen species play an important role in a variety of inflammatory conditions, including arthritis. We demonstrate herein that oxidative stress, induced by exposure of lymphocytes to H(2)O(2), results in a 50% reduction in GRK2 protein levels and GRK activity with no changes in mRNA expression. Treatment of lymphocytes with the tyrosine kinase inhibitor genistein partially reverses the effect of H(2)O(2) on GRK2 levels, although we did not detect direct tyrosine phosphorylation of GRK2. Inhibition of the nonproteasomal protease calpain by calpeptin can prevent the H(2)O(2)-induced GRK2 decrease. In vitro experiments confirm that GRK2 is partially digested by m-calpain in a calcium-dependent way. Functionally, H(2)O(2)-induced decrease in GRK2 levels is associated with an ~70% decrease in agonist-induced beta(2)-adrenergic receptor sequestration. We describe oxidative stress as a novel mechanism for regulation of the intracellular level of GRK2 during inflammatory processes. Moreover, our data demonstrate that oxidative stress may change the functioning of GPCRs via calpain-dependent regulation of GRK2 levels.

Intracellular processing and presentation of T cell epitopes, expressed by recombinant Escherichia coli and Salmonella typhimurium, to human T cells

Vaccines based on recombinant attenuated bacteria represent a potentially safe and effective immunization strategy. A carrier system was developed to analyze in vitro whether foreign T cell epitopes, inserted in the outer membrane protein PhoE of Escherichia coli and expressed by recombinant bacteria, are efficiently processed and presented via human leukocyte antigen (HLA) class I and II molecules by bacterial infected human macrophages. A well-defined HLA-B27-restricted cytotoxic T cell (CTL) epitope and an HLA-DR53 restricted T helper (Th) epitope of the fusion protein of measles virus were genetically inserted in a surface-exposed region of PhoE, and the chimeric proteins were expressed in E. coli and Salmonella typhimurium. Macrophages infected with both recombinant bacteria presented the Th epitope to the specific CD4+ T cell clone, but failed to present the CTL epitope to the specific CD8+ T cell clone. Presentation of the Th epitope by the infected macrophages was inhibited by cytochalasin D, indicating that phagocytic processing of intact bacteria within infected macrophages was essential for antigen presentation via HLA class II. Presentation of the Th epitope to the CD4+ T cell clone by infected macrophages was blocked by brefeldin A and cycloheximide, indicating the requirement of nascent HLA class II molecules for presentation. The efficiency of macrophages to process and present the inserted Th epitope was similar for both the recombinant E. coli and S. typhimurium strains.

Experimental studies of immunologically mediated enteropathy. VI. Inhibition of acute intestinal graft-versus-host reaction in mice by 2'-deoxyguanosine

We have attempted to investigate the relative roles of specific cytotoxic T lymphocytes (CTL) and allospecific suppressor T cells (Ts) in the systemic and intestinal manifestations of acute graft-versus-host reaction (GvHR) in mice. Treatment of adult (C57B1/10 x DBA/2)F1 (BDF1) mice with the suppressor cell-specific toxin 2'-deoxyguanosine (dGuo) inhibited the weight loss and mortality which normally occur after induction of GvHR and C57Bl donor cells. dGuo also delayed the development of a destructive enteropathy as typified by jejunal villus atrophy. Paradoxically, dGuo completely prevented villus atrophy during an acute GvHR in neonatal (CBA x BALB/c)F1 hosts, despite having only a slight ability to inhibit the systemic disease. In both models, dGuo had no effect on the generation of splenomegaly or anti-host CTL, and dGuo-treated mice with GvHR actually had increased proliferative alterations in the intestine, as assessed by crypt hyperplasia. In parallel, dGuo prevented the loss of NK cells which normally occurs in acute GvHR. Thus dGuo inhibits many of the destructive features of systemic and intestinal GvHR without affecting the development of CTL. We conclude that a dGuo-sensitive mechanism causes the transition from a proliferative to a destructive GvHR.

Interleukin 1 in the in vitro antigen-induced antibody response in the human adult and newborn

Previous studies have shown that in vitro stimulation of human B lymphocytes with antigens such as ovalbumin (OA) induces the formation of small antigen-specific plaque-forming cells (PFC) but precludes the activation of the B cells into full-blown antibody-secreting cells. Insufficient production of T cell-derived growth and differentiation factors appears to be the basis of the phenomenon. Furthermore, cord blood B lymphocytes required 100 times less OA to become activated in vitro into antigen-specific PFC, and the distinct antigen-handling capacities of neonatal monocytes are the basis of this result. We have studied the role of interleukin 1 (IL-1) in the in vitro response of B lymphocytes from either cord blood or adult blood to OA. Addition of IL-1 to the B-cell cultures significantly increased the number of PFC, and about 50% of the plaques now appeared to be high-rate IgM anti-OA-secreting PFC. The IL-1-mediated increase in the PFC response was shown to be based on potentiation of T-helper cell activity. The differences between cord blood and adult blood mononuclear cells in the optimal OA concentration required for effective in vitro activation of B cells remained the same upon addition of IL-1. This result shows that the phenomenon is independent of IL-1.

A role for the autonomic nervous system in modulating the immune response during mild emotional stimuli

The role of the autonomic nervous system in the modulation of the immune response to emotional stimuli, was established in rats subjected to the passive avoidance test. An increase in splenic primary antibody response directed against SRBC was found after exposure of rats to the passive avoidance apparatus (novelty). Both local surgical denervation of the spleen and beta-receptor blockade (timolol, 1 mg/kg i.p. 1 h prior to testing) prevented the increase in primary antibody response.

Effects of environmental stimuli on immunoreactivity: further studies on passive avoidance behavior

Rats were immunized against sheep red blood cells (SRBC) immediately after the passive avoidance test; 5 days later the antibody response was measured by determining the number of splenic antibody-secreting B cells. Subjection of rats to habituation trials in the passive avoidance apparatus (apparatus control group) resulted in an enhanced number of antibody secreting cells compared to rats that remained in their home cage. The same phenomenon was observed in rats that were immunized immediately after the learning trial (electric footshock). In animals that showed passive avoidance behavior when tested for retention 24 h after the learning trial, the initially enhanced immune response was down-regulated to the level of rats that remained in their home cage or even lower. The above-mentioned alteration in number of anti-SRBC antibody-secreting cells was only observed in rats that were immunized 15 min after the retention test. In rats that were immunized 1, 4, or 8 h after the retention test no alteration in primary antibody response was observed. In rats of the apparatus control group that were immunized immediately after the retention test an elevated primary antibody response was observed 4, 5, 6, and 7 days after immunization; thus, the changes in immune response were not the consequence of a delayed or accelerated induction of the anti-SRBC response. No change in the absolute number of leukocytes in peripheral blood was observed in the different experimental groups. Moreover, the observed differences in response were not caused by a shift in the percentage of total T, B, Th, or Ts/c cells. The alteration in primary antibody response was only observed in the spleen. The antibody titer in trunk blood did not differ among the different groups and no significant change in number of antibody-secreting cells in the parathymic lymph node was observed. These results show that rats can specifically register different environmental stimuli and as a consequence of that perception there is a change in antibody-secreting cells in the spleen.

Cells involved in the immune response. XXXV. The antigen-specific antibody response in the rabbit is suppressed by thymocytes of allogeneic immunized rabbits (ITSC) and by the non-toxic suppressor factor (ITSF) secreted by these thymocytes

The antigen-specific suppressor cells (ITSC) detected in the thymus of the rabbit 7 days post-iv immunization with sheep or horse erythrocytes (SRBC and HRBC, respectively), and the antigen-specific suppressor factor (ITSF) which the ITSC secrete in culture, inhibit the antigen-specific primary immune response in vivo when injected iv into SRBC and/or HRBC immunized rabbits on Days 0, 3, and 5 (ITSC) or daily on Days 0 to 5 (ITSF) post-primary immunization. The rabbits recover the ability to synthesize the specific antibodies following reimmunization by day 80 post-primary immunization. The primary immune response toward a non-cross-reacting antigen is not inhibited by the antigen-specific ITSC or ITSF. Neither the thymocytes of unimmunized rabbits nor the secretions of these cells in culture can suppress the primary immune response in vivo to either SRBC or HRBC. It must be emphasized that the suppression of the immune response by ITSC and ITSF in the rabbit is antigen-specific. ITSC and ITSF are not cytotoxic to rabbit lymphocytes in vitro. No gross or microscopic changes were detected in any of the lymphoid and nonlymphoid organs of rabbits sacrificed 2 days following 5 daily iv injections of large doses (10 ml) of ITSF. ITSF causes no adverse reaction in vivo since it did not induce morbidity in the rabbits during the 80 days observation period following its injection iv daily for 5 days commencing with the primary immunization.

Modulation of the immune response by emotional stress

The influence of mild, emotional stress was investigated for its effect on the immune system by subjecting rats to the one-trial-learning passive avoidance test. The reactivity of the immune system was tested by determining the proliferative response after mitogenic stimulation in vitro as well as the capacity to generate a primary antibody response in vivo after immunization with sheep red blood cells. Our results demonstrate that exposure of rats to a single electric footshock (learning trial) or habituation to the passive avoidance apparatus, induces an increase of the immune response in vitro and in vivo. Thus, emotional stimuli seem to facilitate immunological responsiveness. However, when the animal is confronted with a conflict situation, as tested by the retention of the avoidance response after a single learning trial, the initially enhanced reactivity of the immune system decreases. It is concluded that the immune system is capable of reacting specifically and immediately to distinct psychological stimuli.

Cells involved in the immune response. XXXIV: Suppressor cells in the thymus of the immunized rabbit capable of secreting a factor which can suppress the secretion of antibodies from antibody-forming cells in vitro

Outbred rabbits were immunized intravenously with 10(9) sheep erythrocytes (SRBC) and/or horse erythrocytes (HRBC) and sacrificed 1 to 60 days later. At the height of the immune response (Day 7 postimmunization), antibody-forming cells identified by their ability to form hemolytic plaques in the plaque-forming cell (PFC) assay were detected only in the spleen. The splenic PFCs were totally inhibited if they were first incubated with the autologous thymus cells (immune thymus suppressor cells or ITSCs) for 4 hr prior to assaying for PFCs. Incubation of the spleen mononuclear cells with cells of any of the other lymphoid organs of the immunized rabbit for up to 6 hr did not inhibit the PFCs to any significant degree. There is no MHC restriction in the suppressor activity of the ITSCs since they could totally suppress the PFCs of autologous and allogeneic 7-day immune spleen cells. Neither thymus cells nor cells of any of the other lymphoid organs of the unimmunized rabbit could inhibit allogeneic 7-day immune splenic PFCs. The ITSCs from rabbits immunized with SRBC could be isolated by rosetting with the immunizing antigen, SRBC, but not with the non-cross-reacting antigens HRBC, human erythrocytes (HuRBC), and rabbit erythrocytes (RRBC), and vice versa, thus demonstrating the antigenic specificity of the suppressor cells. The thymus cells, but not the cells of any of the other lymphoid organs of the SRBC-immunized rabbit, secreted a factor referred to as immune thymus suppressor factor (ITSF) during incubation for 4 hr at 37 degrees C which could, by itself, totally suppress the splenic PFC. ITSF could be absorbed out of solution by incubation with the immunizing antigen, SRBC, but not with the non-cross-reacting antigens HRBC, HuRBC, and RRBC. Similarly, the ITSF secreted by the thymus cells of the HRBC-immunized rabbit could be absorbed out of solution by incubation with the immunizing antigen, HRBC, but not with the SRBC, HuRBC, and RRBC. ITSF is therefore antigen specific as is its parent ITSC. The cells of the lymphoid organs of unimmunized rabbits did not secrete a suppressor factor during incubation in vitro. ITSCs capable of totally inhibiting the PFCs were detected in the immunized rabbits by Day 5 post-primary-immunization; the ITSCs were capable of secreting ITSF which could totally inhibit the PFCs by Day 7 post-primary-immunization. Although the ITSCs were detected in a suppressive state up to Day 40 post-primary-immunization, they lost their capacity to secrete ITSF by Day 21 post-primary-immunization.(ABSTRACT TRUNCATED AT 400 WORDS)

Antigen-specific activation of autoreactive B cells in normal human individuals

The purpose of our study was to determine if normal human B cells can be activated to autoantibody production using an antigen-specific system. For this purpose we investigated the in vitro antibody response to the autoantigen thyroglobulin (Tg) employing soluble or insolubilized Tg (i-Tg) and a B cell growth and differentiation factor (BDGF) to stimulate lymphocytes from healthy individuals. Similar experiments were carried out with the xenoantigen ovalbumin (OVA). The presence of Tg and OVA-reactive B cells was demonstrable by stimulating lymphocytes from tonsil, spleen and blood with a combination of pokeweed mitogen and formalinized Staphylococcus aureus: mitogen stimulation resulted in the generation of IgM anti-Tg and IgM anti-OVA antibody-forming cells (AFC) as detected in a spot enzyme-linked immunosorbent assay. Soluble antigen failed to induce autoantibody production. However, i-Tg or i-OVA did activate normal tonsil and spleen B cells. Differentiation of these activated B cells to IgM AFC required the presence of BGDF, derived from a human T hybrid clone. Preincubation experiments with the particulate autoantigen show that a specific activation signal is provided by the antigen which subsequently renders the B cells responsive to BGDF. i-Tg-dependent stimulation of B lymphocytes could be inhibited by adding free Tg to the cultures; the same applied to i-OVA stimulation. We conclude that the normal human B cell repertoire contains B cells that can be activated to autoantibody production by the autoantigen Tg if the necessary T cell signals are provided. Thus, these B cells are not in an inherently anergic state. Similar mechanisms seem to play a role in the activation of B cells responding to i-OVA and i-Tg.

Patho-anatomical studies in patients dying of AIDS

The incidence of AIDS in Denmark is the highest reported among the countries of Western Europe. This preliminary account is a report of the autopsy findings in 10 patients, 9 homosexual men and 1 woman. Our aim is to provide a detailed description of the patho-anatomical findings, as well as to compare these with corresponding results reported from the United States, with a view to establishing possible geographical differences in the disease picture. The results of the patho-anatomical studies correspond in all essentials to those from the United States. However, it must be stated that no malignant lymphomas were demonstrated in our patients, although the disease can give rise to very pronounced, possibly transitory, lesions in the lymphatic tissue, easily misinterpreted as malignant. Further features that should be emphasized are the often widespread mycobacterial infection found in the intestinal wall in protracted cases, the occurrence of CMV vasculitis, particularly in the adrenal cortex and medulla, and thromboembolic lesions, often demonstrated in a variety of tissues. The studies made so far emphasize the importance of autopsy in AIDS deaths, as it has extended our detailed knowledge of the patho-anatomical lesions associated with certain opportunistic infections. Further, the autopsy findings have been demonstrably significant either for confirming or for rejecting the clinical diagnosis. On the basis of an analysis of the cellular immunological profile in AIDS, parallels can be drawn to the conditions in certain lymphoproliferative diseases. In autopsied AIDS cases, we recommend a standard scheme covering the tissue specimens to be obtained for histological examination. Strict safety precautions should be observed against infection during autopsy.

A monoclonal antibody detecting dipeptidylpeptidase IV in human tissue

Dipeptidylpeptidase IV (DPP IV) occurs among others in exocrine epithelia, hepatocytes, renal tubuli, endothelia, and myofibroblasts of man and laboratory animals. Also T mu lymphocytes and their varying differentiated neoplastic counterparts reveal this enzyme activity. The present paper describes a new monoclonal antibody recognizing DPP IV. Additional efforts have been taken to detect the subcellular localization of DPP IV and its isoelectric focusing pattern in different tissue types. The monoclonal antibody anti-DPP IV (clone II-19) shows a reaction pattern indistinguishable from the corresponding enzymehistochemical reaction. These findings were further substantiated by immunoblotting analysis. In line with the results of direct enzyme measurements in different subcellular fractions a considerable portion of the enzyme is localized in the membrane fraction.

Allocation of the suppressive activity of normal peripheral blood lymphocytes induced by diffusion chamber culture and Con A stimulation to the G2 phase of the cell cycle

Peripheral blood mononuclear cells stimulated either by diffusion chamber culture or by a high Con A concentration exhibit suppressive activity under conditions where no increase in cell number takes place. Instead an accumulation of large cells is observed which, according to their DNA contents, are classified as cells in the G2 phase of the cell cycle. By elutriation separation the suppressive activity is shown to be confined to this cell cycle phase.

Enumeration of (auto)antibody producing cells in human using the "spot-ELISA"

An enzyme-linked immunosorbent assay (spot-ELISA) for individual immunoglobulin secreting cells, which became recently available, was applied to the enumeration of human B lymphocytes secreting specific antibodies of thyroglobulin. Polyclonally activated B cells from patients with auto-immune thyroid disease are incubated in thyroglobulin coated plates. After removal of the cells specific antibodies are visualized by means of an immunoenzyme technique employing agarose to localize converted substrate. Individual specific antibody secreting cells are counted as blue spots using an inverted microscope. Numbers and isotype of spots correlate well with the amount and isotype of secreted antibody as detected with a conventional ELISA. This easy to perform, complement-independent technique offers a useful alternative to conventional plaque forming cell assays.

Induction of antibody to foot-and-mouth disease virus in presensitized mouse spleen cell cultures

Cultures of spleen cells from immunized mice were stimulated in vitro by soluble preparations of purified foot-and-mouth disease virus. Virus-specific antibody, as detected by an enzyme-linked immunosorbent assay, was produced by immune spleen cells but not by normal, nonimmune cells. The optimal specific response was obtained with 1 microgram of virus per ml of culture; as the virus concentration was increased, the production of specific antibody was reduced. For very low concentrations of virus (less than 0.01 microgram per culture), there was tentative evidence of suppression of the specific antibody response. The levels of specific antibody induced were dependent on the source and number of plastic-adherent cells present in the cultures. We intend to use this model system to study further the basis of immunity to foot-and-mouth disease virus.

Antigen-induced plaque-forming cell responses in cultures of peripheral blood mononuclear cells of human neonates and infants

Human cord blood mononuclear cells (CBMC) were stimulated in vitro with a number of T cell-dependent antigens. Antigen-induced B cell activation was measured applying a plaque-forming cell assay for the detection of antigen-specific IgM-secreting B cells. With the exception of diphtheria toxoid, the antigens ovalbumin, sheep red blood cells, Helix pomatia hemocyanin, burro red blood cells, and tetanus toxoid elicited an IgM-plaque-forming cell response in cultures of CBMC to levels obtained for peripheral blood mononuclear cells (PBMC) from adult controls. However, for each antigen used, the antigen dose optimal for the induction of a response was consistently found to be a hundred to a thousand times lower than the concentration of the corresponding antigen optimal for adult PBMC. Longitudinal studies on PBMC obtained from infants between 2 and 30 months of age revealed that a shift of the antigen dose toward concentrations needed to induce plaque-forming cells in cultures of adult PBMC occurs at approximately age 8 months. Our data indicate that various antigens can be used for the in vitro analysis of antigen-specific B cell activation and regulatory T cell functions in studies concerning the ontogeny of the humoral immune response in humans.

Peripheral nerve P2 basic protein and the Guillain-Barré syndrome. In vitro demonstration of P2-specific antibody-secreting cells

An immune response to the peripheral nerve basic protein P2 may be operative in the pathogenesis of the Guillain-Barré syndrome (GBS). A method is described for the purification of P2 of human origin. Purified P2 was used to investigate whether lymphocytes derived from peripheral blood of GBS patients are capable of producing P2-specific antibodies after stimulation with the antigen in vitro. Peripheral blood lymphocytes (PBL) from 5 GBS patients, from 3 patients with chronic idiopathic polyradiculoneuropathy (CIP) and from 3 normal controls were cultured in vitro in the presence of P2. PBL from the 5 GBS patients were shown to generate an antigen (P2)-specific antibody response. Contrariwise, PBL from the 3 CIP patients as well as from the 3 normal controls did not show this specific response.

Cold lymphocytotoxic antibodies in systemic lupus erythematosus

Optimum conditions were established for the assay of cold lymphocytotoxic antibodies (cLCTA) in serum from patients with systemic lupus erythematosus (SLE). The optimum temperature of the incubation step with complement was 15 degrees C. For target cells incubated with dextran a significantly higher percentage of damaged cells (p less than 0.005), a faster rate of cell damage (p less than 0.001) and a requirement for less complement was observed than for target cells not incubated with dextran. Under optimum conditions in the cytotoxicity assay, 62% of SLE sera damaged more than 60% of the target cells, whereas 73% of the sera from control donors damaged less than 20% of the target cells. In multiple serum samples obtained during follow-up of 30 patients with SLE, the serum cytotoxic activity or titer of cLCTA fluctuated and did not relate to clinical symptoms of disease activity. In sera obtained during active disease the cytotoxic activity was related to the anti-dsDNA antibody level and with levels of circulating immune complexes measured by the Raji cell assay and the indirect granulocyte phagocytosis test. We found no restricted reactivity of cLCTA against phenotypically distinct T-lymphocyte subpopulations with different immunoregulatory functions. The reactivity pattern of cLCTA towards the various T-lymphocyte subpopulations was not related to disease activity. We conclude that cLCTA in patients with SLE represent an epiphenomenon, being the result of a hyperreactive B-cell system rather than the cause of the disease.

Suppressor cells in the human maternal-fetal relationship

The mixed lymphocyte culture (MLC) of maternal and newborn (cord) cells is significantly weaker than that of father-newborn and control-newborn cultures. This hyporeactivity was found not to be due to an impaired function or tolerance of either the maternal or neonatal cells. We investigated the possibility that a specific, in vivo-induced suppressor cell was active in the diminished maternal-newborn reaction. Suppressor cells were found to be active in both the stimulating and responding populations in the unidirectional MLC. The removal of TG cells from the responding (maternal or newborn) population resulted in an increase of reactivity specific for the corresponding stimulating population (newborn or maternal). The suppressor activity within the stimulating population was carried out by a radiosensitive cell, which did not require proliferation to exert its effect. We suggest that the observed hyporeactivity of maternal-newborn mixed lymphocyte cultures is due to the modulation of the reaction by specific, in vivo-induced suppressor cells.

New ultrastructural observations: parallel tubular arrays in human T gamma lymphoid cells

T gamma cells are E-rosetting cells bearing Fc receptors for IgG (E+, Fc gamma + cells). Third population (non-T, non-B) lymphoid cells are also Fc gamma + cells and contain unique inclusions called parallel tubular arrays (PTA). Although T gamma cells and third population lymphoid cells should belong to a similar population of cells, previous ultrastructural studies on purified T gamma cells have failed to reveal the presence of PTA. In this study, we have unequivocally demonstrated PTA in the majority of T gamma cells using simple rosetting techniques. A total of 76 EA hu-rosettes and 108 EA ox-rosettes prepared from an E+ enriched fraction (using sheep erythrocytes as marker particles) were directly examined by electron microscopy. PTA were found in 87% of the EA hu-rosettes and 82% of the EA ox-rosettes. Ammonium chloride, commonly used in other laboratories to lyse erythrocytes during the purification procedure was found to cause a marked decrease in the number of ultrastructurally distinct PTA profiles. In contrast, hypotonic lysis had no effect on cellular ultrastructure. This study showed for the first time that T gamma cells are ultrastructurally similar to other Fc gamma + lymphoid cells and contain PTA as a distinct marker. The significance of our findings to the basic function of this E+ Fc gamma + lymphoid population is discussed.

Surface receptors and immune activity of purified human circulating mononuclear cells. IV. The demonstration of seven subclasses of T cells in the circulation of the normal individual: the cytotoxic activities of these cells

T lymphocytes were isolated from monocyte-depleted mononuclear cells of normal individuals by rosetting them with sheep erythrocytes. These purified T cells were preferentially depleted of cells with receptors for FcG (TG cells), FcM (TM cells), or C'3 (TC cells) by rosette formation with EA(G), EA(M), and EAC, respectively, before or after incubation for 24 hr in medium 199 fortified with fetal calf serum (20%). The unfractionated lymphocytes and the purified and the depleted T cells were analyzed for receptors to FcG, FcM, and C'3 and for cytotoxic activity in the natural killer (NK), antibody dependent cell-mediated cytotoxicity (ADCC), and mitogen-induced cell-mediated cytotoxicity (MICC) assays. The TG and TC cells were detected among the freshly isolated T cells, whereas the TM cells were detected only following 24 hr of incubation. Removal of TC cells from the 24-hr-cultured T cells resulted in removal of all the TC cells and in the concomitant removal of the majority of TM cells. Similarly, removal of TM cells from the 24-hr-cultured T cells resulted in the elimination of all TM cells as well as the majority of TC cells. These results demonstrate the in vitro generation of T cells with receptors for both FcM and C'3 (TM+C cells). Ten percent of the freshly isolated TG cells possessed detectable receptors for C'3 and/or FcM. These cells constitute the TG+C and TG+M lymphocytes. Support for consideration of these receptor-bearing cells as unique and stable cells is provided by the finding that TM and TC cells maintained in culture for up to 72 hr do not generate other receptors but retain the single receptor which characterizes each of these cells. Only a small percentage of cultured TG cells generate receptors for C'3 and FcM. It may therefore be concluded that the TG, TM, and TC cells are stable unireceptor-bearing cells. The TG, TM, TC, TG+C, TG+M, and TM+C lymphocytes account for approximately 50% of the circulating lymphocytes. Whether the remaining cells, the T null or TN cells, constitute the precursors for any or all of the receptor-bearing T cells remains to be determined. Unfractionated freshly isolated T cells were highly cytotoxic in the NK and PWM-mediated MICC assays but were relatively inactive in the ADCC, naturally occurring cell-mediated cytotoxicity (NOCC), and PHA- and Con-A-mediated MICC assays.(ABSTRACT TRUNCATED AT 400 WORDS)

Subtyping of chronic lymphocytic leukemia of T-type by dipeptidylaminopeptidase IV (DAP IV), monoclonal antibodies, and Fc-receptors

The authors have recently provided evidence for a restricted occurrence of the enzyme dipeptidylaminopeptidase IV (DAP IV) in normal human Tmu lymphocytes as far as blood and bone marrow cells are concerned. In this report, this issue has been extended to cases of chronic lymphocytic leukemia (CLL) along with T-monoclonal antibodies of OKT series (OKT4, OKT8) and Fc receptors for IgM (Tmu) and IgG (Tgamma). Seven of eight cases of T-CLL were DAP IV-positive, whereas all B-CLL cases like normal B-cells were invariably enzyme-negative. Parallel studies with OKT antibodies and Fc receptors showed that the cases positive to DAP IV also revealed OKT4 reactivity and, to some extent, Fc IgM receptor. In a single DAP IV-negative T-CLL with azurophilic granules, the leukemic cells were shown to be reactive for OKT8 and bore Fc IgG receptor. It was inferred that DAP IV represents a reliable marker for T-CLL derived from the OKT4 and Tmu positive subsets of T-lymphocytes, which encompasses the T-helper cell cohort.

Immunoregulatory T cell subpopulations in man: dissection by monoclonal antibodies and Fc-receptors

Until now, most of the studies on regulatory T cells have been based on culture systems in which human peripheral blood cells are stimulated by polyclonal stimulators like Pokeweed Mitogen (PWM). Our present contribution, however, deals with T cell-mediated regulation of the antigen-induced B cell activation, which exclusively leads to an antigen-specific IgM production (Heijnen et al. 1979a). Some authors' reports on regulatory activities of T cells, as tested in systems using polyclonal stimulators, differ from ours. This may be due to: a) as a result of polyclonal stimulus, various types of regulatory T cells are activated at the same time b) in contrast to a primary antigen, a polyclonal stimulator induces a rapid proliferation of the various regulatory T cells c) a polyclonal stimulator induces the differentiation of B cells in various maturational stages, that might each require additional or different regulatory signals. For example, Thomas et al. (1981) have shown that freshly isolated T4+ cells can induce suppressor activity in unprimed T8+ cells in the presence of PWM, whereas T4+ cells, precultured for 24 h in the presence of PWM, can exert a suppressor activity themselves without an apparent need for T8+ cells. In the antigen-specific system, however, we have neither been able to detect T suppressor effector activity in a population of primed T4+ cells, nor been able to demonstrate T suppressor inducer activity in unprimed T4+ cells (Heijnen et al. 1982a). Therefore the state of activation of the total T4+ population will dictate the balance of the total T helper and T suppressor activity. As a result of proliferation induced by polyclonal mitogens, small subsets of regulatory T cells, which are functionally undetectable in the primary antigen-specific assay, can expand sufficiently to have a measurable effect. Thomas et al. (1980) have shown that the T4+ suppressor inducer cell in the PWM system is radio-sensitive, which is in contrast with our data in the antigen-specific system. This may imply that we are looking at different subsets of T suppressor inducer cells in these different systems, but it might also indicate that T suppressor inducer cells need to proliferate in order to be able to measurably regulate the large pool of responding cells generated in the PWM system. Apart from such quantitative effects, polyclonal B cell activators like PWM are capable of inducing the differentiation of B cells in various maturational stages (Kuritani & Cooper 1982, Stevens 1982, Peters & Fauci 1983). Since it is highly likely that the regulation of these various B cell subsets might require different regulatory signals, the PWM model might be a very complicated model to study regulatory effects of single T cell subsets.(ABSTRACT TRUNCATED AT 400 WORDS)

Antigen-induced human T cell help. Precursor frequency, radiation sensitivity, and allogeneic effects

We have recently noted marked differences between the in vitro responses of human B lymphocytes to stimulation with soluble antigens vs. stimulation with mitogens. In the present study, these differences were analyzed in terms of the precursor frequencies for the T cells and B cells involved and in terms of the radiation sensitivity of the T cells providing help in the two systems. Marked differences were found between antigen-induced and mitogen-induced systems with regard to T cell precursor frequencies and radiation sensitivity. In contrast, the precursor frequencies for the B cells involved in the two systems were approximately the same. In addition, having developed a system for the study of human antigen-specific B cell responses, we were interested in delineating the nature of the allogeneic effects that might be operative in this system. Marked allogeneic effects, both positive and negative, were noted in this system and will need to be taken into account in any studies that try to address the question of the genetic restriction, if any, that exists in human antigen-specific T cell-B cell collaboration. Appreciation of the marked differences between the antigen-specific and mitogen-induced activation and immunoregulation of human B cell responses will be of importance in understanding the relationship between specificity and nonspecificity of antibody production in normal and disease states.

Antigen-specific plaque-forming cell response of human cord blood lymphocytes after in vitro stimulation by T cell-dependent antigens

Mononuclear cells isolated from human cord blood (CBL) of full-term neonates were stimulated in vitro with a dose range of T cell-dependent antigens, i.e. ovalbumin or sheep erythrocytes, and tested for the capacity to mount an antigen-specific plaque-forming cell (PFC) response. Both of the antigens used induced in CBL a PFC response with the same kinetics of PFC formation and of the same magnitude as found in cultures of adult peripheral blood lymphocytes (PBL). However, optimal PFC responses in CBL were obtained at a hundredfold lower concentration of the antigens compared with the optimal antigen doses for the induction of a PFC response in adult PBL. This phenomenon was further investigated with respect to the antigen dose dependency of the activation of neonatal B cells and neonatal regulatory T cells. The induction of a PFC response in CBL at antigen concentrations that were suboptimal for adult PBL showed a correlation with the particular antigen dose requirements for the activation of B cells and T helper cells in neonates. Furthermore, the findings suggest that the decrease of the PFC response in CBL stimulated with supraoptimal doses of antigen was not caused by the induction of unresponsiveness at the B cell level or by interference of pregnancy-associated substances with the PFC response, but was rather the result of the activation of antigen-specific T suppressor cells. Neonatal T suppressor cells were activated at antigen concentrations that generated T helper activity in the adult. Thus, although neonatal B cells possess the intrinsic capacity to mature into antigen-specific PFC, the conditions for effective activation of neonatal T cells regulating the B cell response differ from those for the activation of adult regulatory T cells.

Precultured and fresh human T-cells suppress the mitogen response of autologous lymphocytes

Human T-lymphocytes, after culture at 37 degrees C for 48 h, suppressed the Con A-induced blastogenesis of fresh autologous lymphocytes. Both Fc gamma receptor-positive and -negative T-cell subsets were active as suppressors. Non-T-cells failed to show such a phenomenon. Similarly, freshly isolated T-cells, and Fc gamma receptor-positive T-lymphocytes also suppressed the blastogenic response. Thus, preculture is not required to obtain "suppressor cells". The suppression of mitogen responses therefore seems to be an inherent property of T-cells.

Experimental study of antibiotic-induced immunosuppression in mice. II. Th, Ts and NC cell involvement

In penicillin(pen), streptomycin(str), kanamycin(kan) and tetracycline(tet)-treated CBA/J adult mice, no difference was noticed as concerned spleen T "helper" (Th) cell activity, as studied by means of response to PHA of X-irradiated/whole T fraction cell mixtures in vitro. On the contrary, in erythromycin(erm), colistin(col) and chloramphenicol(chl)-treated groups, Th cell activity was significantly decreased. On the other hand, spleen T "suppressor" (Ts) cell activity (assayed by response to PHA of mixtures containing pre-incubated with Concanavalin A and whole T cells, respectively) was augmented in samples arising from chl-treated group. These results are also supported by experiments testing Th or Ts soluble factors, induced in spleen T cells belonging to each antibiotic-treated group and purified by affinity chromatography (Concanavalin A-Sepharose 4B columns). Thus, it was confirmed both Th cell deficiency in erm, col or chl-groups, and Ts cell augmentation in chl-group. As regards spleen "natural cytotoxic" (NC) cell activity, as tested in a xenogeneic "target" cell substrate, a diminished cytotoxic capacity manifested chl-group-derived NC cells, possibly by richness in own "non-specific suppressor" (NSS) cells. NC cell samples in vitro supplemented with NSS cells arising from suckling mouse spleens and a lower cytotoxic activity, in a larger extent in chl-group-derived NC cells, as compared to other groups. The pre-incubation of control-group-NC cells with several antibiotic preparations in vitro was followed by decrease of the cytotoxic values in erm, col and chl-samples, suggesting a drug-induced NC receptor "masking", that prevented "target" cell recognition in mice--II. In the case of NSS addition in vitro, as strong inhibition of the cytotoximity occurred in chl-treated NC cells derived from the control group, that proves a possible chloramphenicol-induced immunodepression by potentiation of NSS inhibitory effect on NC cells. Based upon data from the present work, as well as from the previous work, the authors suggest a classification of several mechanisms by which the antibacterial antibiotics can act as immunosuppressive.

Cytochemical reactivity of T mu lymphocytes in human lymphatic tissue for dipeptidylaminopeptidase IV

The enzyme dipeptidylaminopeptidase IV (DAP IV; EC 3.4.14.-) was recently shown cytochemically to be confined, in blood and bone marrow, to human T cells bearing Fc receptors for IgM (T mu lymphocytes). This observation, confirmed by direct biochemical tests, stimulated us to study the histochemical distribution of DAP IV in normal human lymphatic tissue. In cryostat sections of lymph node, tonsil and thymus, DAP IV was detectable only in lymphocytes, Hassal's corpuscles and the endothelia of vessels. The distribution pattern of DAP IV-positive lymphocytes accorded well with results obtained with human T cell antisera. Compared to cytochemical reactions for other enzymes, such as acid esterase, DAP IV has the advantage that it does not stain monocytes, B lymphocytes or other mononuclear cells. Further, it does not depend on a particular type of staining pattern like, for example, the dot-like reaction product of acid esterase in T lymphocytes. Since the reaction for DAP IV remains more or less unchanged in month-old sections, it is easily adaptable to routine work and has the potentiality of being applied to the diagnosis of T cell lymphomas.

Antigen-specific human T-cell hybridomas with helper activity

Human T cell hybridomas were produced by fusing the hypoxanthine phosphoribosyltransferase-deficient line of the human T cell lymphoma Jurkat with a continuous line of normal human T cells specific for tetanus toxoid (TeT). The hybridomas were selected for their ability to produce interleukin 2 after exposure to TeT on semiautologous monocytes and for their ability to bind to TeT-pulsed semiautologous monocytes. These antigen-specific T hybridomas demonstrated potent helper activity for semiautologous B cells as determined by the production of high levels of anti-TeT antibody in vitro.

Characterization of human T suppressor-inducer, -precursor and -effector lymphocytes in the antigen-specific plaque-forming cell response

Suppression of an antigen-specific plaque-forming cell response of human blood lymphocytes can be effected by T mu+ cells that have been primed previously by antigen in vitro for 6 days. While lacking the capacity to suppress the plaque-forming response directly, these primed T mu+ suppressor-inducer cells stimulate a subpopulation of unprimed T mu gamma- cells to differentiate to T gamma + suppressor-effector cells. The T mu+, T gamma+ and T mu gamma- subsets have been shown to be heterogeneous populations of cells. Therefore, the functionally defined T suppressor-inducer, -precursor and -effector cells were characterized by OKT monoclonal antibodies and by the capacity to form rosettes with autologous erythrocytes (ar+). Evidence will be presented that in vitro a T4+mu+ar- cell induces a T8+mu gamma-ar+ precursor cell to differentiate to a T8+gamma+ar- suppressor-effector cell. A similar T suppressor-effector cell can also be isolated directly from peripheral blood of normal donors.

T lymphocyte subpopulations defined by monoclonal antibodies and FC receptor binding in relation to immunosuppression in vaccine-induced rubella infection

Lymphocyte stimulation tests and determination of T lymphocyte subpopulations were undertaken before and 7-11 days after rubella vaccination of healthy subjects. The proliferatory response of blood mononuclear cells to phytohemagglutinin (PHA) and purified protein derivate was suppressed after vaccination, as was the immunoglobulin production of pokeweed mitogen (PWM) stimulated cultures. After removal of phagocytic cells the response to PHA was still suppressed after vaccination in most cases, but when the cultures were depleted of non-T lymphocytes the suppression was no longer demonstrable. The proportion of T lymphocytes with receptors for the Fc part of IgG increased after vaccination, whereas there was no significant change of the T lymphocyte subpopulations identified with monoclonal antibodies directed at the suppressor/cytotoxic or helper T cell subsets.

Antibody mediated regulation of immune responses. I. Enhancement of specific antibody responses through IgM antibodies

Injection of monoclonal IgM antibodies to sheep red blood cells (SRBC) 2 h before immunization with a low dose of antigen (Ag) specifically enhances the direct and indirect plaque-forming cell response. This enhancement was specific: the specific antigen had to be present; the plaque-forming cell (PFC) response to TNP-Ficoll- or bromelein-treated mouse red blood cells was not enhanced; the PFC response to SRBC was not enhanced by injections of monoclonal antibody to TNP. The optimum conditions for enhancement were found to be dependent on both the dose and the time of administration of antibody in relation to antigen. The possible mechanisms for this enhanced antibody response are discussed.

Concanavalin A induces suppressor cell activity in both T gamma and T non-gamma cells: most of the suppressor cells do not carry HLA-DR antigens

Concanavalin A (Con A) stimulation of T lymphocytes for 48 h induced a dose-dependent increase in the percentage of T gamma cells, and proliferation of these cells was dependent on pre-existing T gamma cells. Con A stimulation also induced a dose-dependent increase in suppressor cell activity as measured in a Con A/mixed lymphocyte culture assay. Removal of T gamma cells before stimulation with Con A did not influence suppressor cell activity, whereas depletion of T gamma cells after Con A stimulation significantly reduced the suppression. Treatment of T lymphocytes with monoclonal anti-HLA-DR antibodies and complement significantly increased the percentage of T gamma cells and also increased the suppressor cell activity, both when the cells were treated before and when they were treated after Con A stimulation. Similarly, increased suppressor cell activity was also seen when T mu cells were removed. The results indicate that Con-A-induced suppressor cells are recruited from both T gamma and T non-gamma cells and also suggest that most of the Con-A-induced suppressor cell activity is exerted by HLA-DR-negative cells.

Enzymecytochemical heterogeneity of human chronic T-lymphocytic leukemia as demonstrated by reactivity to dipeptidylaminopeptidase IV (DAP IV; EC 3.4.14.4)

The observation that the dipeptidylaminopeptidase IV (DAP IV; EC 3.4.14.4) occurs exclusively in T mu lymphocytes, stimulated the following study on cases of chronic lymphocytic leukemias. Thirty cases of human chronic lymphocytic leukemia were subjected to the DAP IV reaction in addition to the usually applied cytochemical and immunological tests (acid alpha-naphthyl acetate esterase, acid phosphatase, rosetting with sheep erythrocytes and surface Ig). DAP IV activity was measured directly in normal granulocytes, monocytes, B and T lymphocytes as well as in lymphocyte suspensions of leukemic cases. On a cytochemical level granulocytes, monocytes, B lymphocytes and all 24 cases of B-CLL were found to be DAP IV negative, though some of the latter showed positive reactions for AcE and AcP. From the six cases of T-CLL, five were positive to DAP IV cytochemically. No discrepancies were observed between cytochemical and biochemical results. It is concluded that DAP IV is a reliable and easy to perform marker for T mu lymphocytes and their neoplasias. The results have been interpreted as further evidence for a clonal nature of T-cell neoplasias.

Immune response potential to poly(Tyr,Glu)-poly(DLAla)--poly(Lys) of human T cells of different donors

Human peripheral blood T cells of normal donors were activated in vitro with autologous adherent cells pulsed with poly(LTyr,LGlu)-poly(DLAla)--poly(LLys) [abbreviated (T,G)-A--L]. The "educated" T cells were tested: (i) for their ability to produce a (T,G)-A--L-specific T cell-replacing factor in the cooperation with B cells for antibody responses in vivo or in vitro and (ii) for their ability to proliferate in the presence of a second stimulus of (T,G)-A--L. Results of screening of 66 donors demonstrated that educated T cells of about 50% of the donors produced an active (T,G)-A--L-specific factor, whereas activated cells of only half of the factor producers were capable of proliferating in the presence of the antigen. Thus, as reported for all other species studied, human individuals differ in their response potential to (T,G)-A--L.

The role of extracellular DNA in the transfer of information from T to B human lymphocytes in the course of an immune response

Human lymphocytes obtained from donors exhibiting different allotypes were separated into B- and T-enriched subpopulations and cultured in the presence or absence of Herpes simplex virus inactivated by U.V. Isolated B or T cell suspensions did not produce any antiherpetic activity. The B lymphocytes cultured in the presence of the supernatant collected from virus-exposed T cells or in the presence of DNA extracted from this supernatant, synthesized an antiherpetic antibody carrying allotypic markers of the T cell donor.

Subpopulations of T lymphocytes in patients with ankylosing spondylitis

Subpopulations of human blood T lymphocytes were determined in 20 patients with ankylosing spondylitis and in 20 healthy individuals. The proportion of T lymphocytes with receptors for the Fc portion of IgG (TG cells) was increased in 9 patients. The proportion of T lymphocytes bearing receptors for the fc portion of IgM (TM cells) was within the range found in healthy controls in all but 4 patients, who had a decreased level of TM cells.

Defective immunoregulation in multiple sclerosis

Imbalances in T cell subpopulations have been reported in multiple sclerosis (MS). In the present study of 31 MS patients, the percentage of T cells with Fc receptors for IgG (Tg) was found to be increased in patients with chronic progressive disease, and another T cell subset binding to the Raji B lymphoid cell line was decreased. An inverse correlation (r = -0.675; < 95% confidence limit) was found between these two subsets, suggesting that they vary inversely in MS. The mitogenic responses of MS mononuclear cells, isolated T cells, and recombinet T and non-T cells to the lectins phytohemagglutinin and pokeweek mitogen (PWM) did not differ from those of normal cells. However, more immunoglobulin (Ig)-producing cells were generated in a PWM-driven system with cells from MS patients than with cells from age-matched controls (p < 0.05). Autologous recombination of separated T and non-T cells did not significantly modify these results. T cells from MS patients added to B cells from normal controls exerted an effect that was related to their percentage of Tg cells; that is, values above 15% were associated with a suppression of Ig production, whereas for Tg values below 12%, a helper effect or no modification was observed. These results suggest that changes in T cell subsets in MS are related to changes in functional ability to modulate Ig production by normal B cells. However, MS B cells partly escape regulation by their own T cells, suggesting an associated B cell hyperactivity.