Regulation of B cell activity in man: role of T cells

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.

Generation of high-rate ovalbumin-specific antibody-secreting cells in cultures of human peripheral blood B cells obtained from non-immunized blood donors

When human peripheral blood B cells are cultured for 6 days with the T cell-dependent peptide antigen ovalbumin (OA) in the presence of antigen-presenting cells and helper T cells, plaque-forming cells (PFC) are generated. These OA-induced PFC differ from the conventional high-rate antibody-secreting PFC formed after stimulation of B cells with recall antigens (e.g. tetanus toxoid) in that they secrete antibody at a very low level. Previous studies have shown that OA-induced PFC are B lymphocytes in an early activation state rather than cells that have differentiated into plasmablasts. The apparent arrest in the maturation of OA-induced PFC in an early activation phase can be overcome by simultaneous stimulation with interleukin 2 (IL-2) and gamma interferon (IFN-gamma). The isotype of the OA-specific antibodies secreted, however, are only of the IgM class, demonstrating that an isotype switch does not occur.

Morphological differentiation of human lymphocyte subpopulations following polyclonal stimulation with bacteria and lectin

Mononuclear cells (MNC) were stimulated with different heat-treated gram-positive and -negative bacteria, and the lymphocyte subpopulation interaction, the proliferative response, and the immunoglobulin secretion were analyzed. It can be demonstrated that beta haemolytic streptococci and Staphylococcus aureus have a similar stimulation pattern: early stimulation of helper T cells, cell contacts of helper T cells and B cells, maximum proliferation on day 5 and 7, and Ig secretion peak on day 7. Klebsiella pneumoniae and Yersinia enterocolitica do not cause proliferation, while Ig secretion is seen on day 5. No cell contacts and no T cell stimulation are seen in the Klebsiella culture, whilst Yersinia causes slight helper T cell activation. In contrast, PHA induces strong T cell stimulation, proliferation and expansion of the suppressor T cell subpopulation. Leu 7-positive lymphocytes are not activated by any of these stimulants.

T-cell inducers of suppressor lymphocytes control liver-directed autoreactivity

The sensitisation of helper T cells of patients with autoimmune chronic active hepatitis to a liver-cell membrane-expressed asialoglycoprotein receptor protein is shown to be associated with a defect of T cells that specifically induce suppressor lymphocytes. These lymphocytes are found in an activated state in the peripheral blood of healthy people and may form part of an immunoregulatory network which actively prevents autoimmunity.

The essential role of L-glutamine in lymphocyte differentiation in vitro

The biochemistry of human B lymphocyte differentiation to plasma cells is incompletely understood. L-glutamine appears to be required for both lymphoblastic transformation and plasma cell formation in pokeweed-mitogen-stimulated human peripheral blood mononuclear cell cultures. Cells cultured with pokeweed mitogen in glutamine-deficient RPMI-1640 with 10% heat-inactivated and dialyzed fetal bovine serum were unable to incorporate 3H-thymidine or undergo morphologic lymphoblastic transformation assessed at 72 hours. However, 3H-thymidine incorporation could be maximally restored with as little as 0.08 mM L-glutamine or by using nondialyzed heat-inactivated fetal bovine serum, containing approximately. 1 mM L-glutamine. In subsequent cultures, using glutamine-deficient RPMI-1640 with 10% nondialyzed heat-inactivated fetal bovine serum, lymphoblastic transformation was equivalent with or without additional L-glutamine supplementation. However, only cultures with 2 mM L-glutamine supplementation underwent plasma cell differentiation as assessed by cytoplasmic staining with fluorescein-conjugated anti-immunoglobulin. When the kinetics of cellular immunoglobulin synthesis and secretion were analyzed by 3H- leucine incorporation into immunoglobulin, synthesis was 2-5 fold greater, and secretion 3-10-fold greater in cell cultures with 2 mM L-glutamine supplementation. By electron microscopy, only the glutamine-supplemented cells showed development of rough endoplasmic reticulum consistent with active immunoglobulin production. L-glutamine supplementation had no apparent effect on cell recovery, viability, % B cells, % T cells, % monocytes, or % helper and suppressor T cells. Thus, L-glutamine is essential for both lymphoblastic transformation and plasma cell differentiation. Future investigation of the selective nutritional requirements of cultured cells should yield further insights into the biochemical control of immune cell differentiation and function.

Cardiopulmonary bypass and host defense functions in human beings: II. Lymphocyte function

In 47 patients undergoing open-heart surgical procedures, the influence of cardiopulmonary bypass (CPB) on lymphocyte function was investigated by studying in vitro the mitogen responses of lymphocytes in whole blood cultures. Subnormal mitogen responses before operation that likely resulted from dexamethasone medication were found in half of the patients studied. During operation, changes in phytohemagglutinin responses were uniform in a group of 23 patients. No significant effect of anesthesia and operation was observed until the patients were heparinized (i.e., before CPB). At the end of operation, the phytohemagglutinin response was below normal. In a group of 24 other patients, postoperative mitogen responses were studied. A tendency toward restoration of mitogen responses was observed in most patients the first morning after operation. However, no uniform pattern of normalization of mitogen responses was found. In an attempt to relate postoperative mitogen responses to trauma resulting from CPB, we observed that perioperative (in comparison with postoperative) administration of blood coincided with a significantly higher incidence of subnormal phytohemagglutinin and pokeweed mitogen responses on postoperative day 1. No correlation between laboratory data and clinical findings could be established.

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.

Immunological aspects of retinoids in humans. II. Retinoic acid enhances induction of hemolytic plaque-forming cells

The effects of retinoic acid (RA) on the induction of antibody-producing cells from human tonsillar lymphocytes sensitized to sheep erythrocytes (SRBC) have been evaluated. Our results indicated that 10(-5) to 10(-7) M RA caused up to a three-fold increase in the number of plaque-forming cells (PFC) and a qualitative increase in the size of the plaques during the induction of PFC in 5- to 7-day cultures. Enhancement also occurred when tonsil cells were preincubated with RA for 24 hr and then washed, or when RA was added any time in the first 4 days after initiation of the culture. When T- and B-cell fractions were pretreated with RA for 24 hr, washed, and recombined with SRBC, RA-induced augmentation of PFC occurred only in conjunction with RA treatment of the B-cell fraction. Pretreatment of the T-cell fraction had no effect on PFC induction or on the RA-enhanced response when the B-cell fraction was simultaneously treated with RA. Other experiments suggested that RA did not modulate PFC induction by influencing regulatory functions of adherent accessory cells. Our study demonstrates that RA can enhance human antibody responses and shows that this effect is not caused by increased activity of T cells or adherent accessory cells, but is instead the result of a direct effect of RA on B-cell populations.

Immunohistochemical identification of lymphocyte subsets and accessory cells in human hyperplastic lymph nodes. The functional significance of the compartmentalization of lymphoid tissue

Biopsies from 21 lymph nodes with benign hyperplasia were examined by immuno-enzymatic labelling of frozen sections with a panel of monoclonal antibodies. B-cells (B1+, HLA-DR+, C3b receptor+/-) localized in primary follicles, secondary follicles, and areas adjacent to the subcapsular sinus. The B-cells in primary follicles and mantle zones of secondary follicles were indistinguishable ( SmIgD +, SmIgM +, CyIg -, T10-, CALLA-). B-cells adjacent to the subcapsular sinus demonstrated a higher density of SmIgM , and a weaker expression of SmIgD . The germinal centre cells showed a more differentiated phenotype ( SmIgD -, SmIgM +, CyIgM +/-), and also expressed T10 and CALLA. T-cells ( Lyt3 +, Lyt2+, Leu4 +, OKT6-, OKT10 -) localized in paracortial and interfollicular areas, and demonstrated a relative predominance of T-helper/inducer cells ( Leu3 +). T-helper/inducer cells were also identified in secondary follicles. The B-cell areas contained dendritic reticulum cells (R4/23+, C3b-receptor+). Interdigitating reticulum cells (HLA-DR+, OKT6+/-) localized in T-cell regions. The cells in sinuses demonstrated monocyte/macrophage properties (MO2+, Ig+, C3b-receptor+, HLA-DR+/-).

Rapid screening for humoral immune deficiency

A preliminary report on a fast, easy and inexpensive screen-test for the detection of humoral immune deficiency is presented. The method is based on the presence of heterophilic antibodies in normal human serum. Multitested normal individuals and immunodeficient patients showed a clearcut dichotomy in this screening procedure.

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)

Control of cell differentiation during proliferation. I. Monocytic differentiation of HL-60 promyelocytes

The cell proliferation relating an uncommitted precursor cell to a differentiated terminal cell has been quantitated. HL-60 promyelocytes, a bipotent precursor cell capable of differentiating along either the myeloid or monocytic pathway, were induced by a human lymphocyte-conditioned medium (CM) to differentiate into macrophage-like cells. The promyelocytes had a generation time of approx. 42 h. Most promyelocytes which differentiated became macrophage-like cells after only one cell division. Some, a minority, underwent more than one division. The time between induction of differentiation and expression of differentiated characteristics could thus be very short. Labelled S-phase promyelocytes could differentiate after traversing S. G2 and undergoing mitosis. Some, approx. 21%, required a subsequent complete cell cycle before differentiating. The data suggest a model in which cells must undergo a S-phase-specific differentiation control event in the presence of CM in order to differentiate in the subsequent G1 phase. This model proposes that a discrete time in S phase exists when cells are susceptible to exogenous regulation directing them to yield differentiated daughter cells.

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.

Radioimmunoassay of human IgG, IgA and IgM

Radioimmunoassay procedures for the quantitation of nanogram quantities of human immunoglobulin are described. The techniques have been successfully used to measure immunoglobulin secretion in culture supernatants by cultured human lymphocytes. Compared with previously published assays to assess lymphocyte function in vitro these procedures are simple, quick and reliable. A comparison of double-antibody and solid-phase radioimmunoassay is made. Similar sensitivity and variability in IgG and IgA assays were observed but it was not possible to develop a reliable double antibody radioimmunoassay for IgM. The solid-phase assay has several advantages over the double-antibody radioimmunoassays being quick to perform and using standard commercial reagents without necessity for exhaustive absorption.

Induction and abrogation of suppressor cell function in humans: effect on B cell activation by different polyclonal activators

In a reverse plaque forming cell (PFC) assay, the effect of concanavalin A (Con-A)-induced suppressor cells on polyclonally activated B lymphocytes was studied. Differentiation to PFC, as induced by pokeweed mitogen (PWM), Staphylococcus aureus or Epstein-Barr virus (EBV) was in all cases suppressed by the addition of ConA-pretreated cells. The EBV-stimulated cells showed the smallest PFC response and appeared least amenable to suppression. IgA-secreting cells were less suppressible than IgM- and IgG-secreting cells regardless of the polyclonal B lymphocyte activator used. The suppressor cells were radiosensitive.

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.

Human T cell lines with antigen specificity and helper activity

Human T blasts, obtained by stimulation of peripheral blood mononuclear cells (PBM) with tetanus toxoid, diphtheria toxoid or Candida albicans, were expanded in long-term culture using alternate periods of antigen restimulation and growth in media containing interleukin 2. The cells gave a proliferative response only to the antigen originally used for stimulation. Such as response was strictly dependent upon the presence of autologous but not of allogeneic mitomycin C-treated mononuclear cells. When added to autologous PBM depleted of E-rosetting cells together with the specific antigen, the T blasts induced a polyclonal proliferation and differentiation of B cells. Allogeneic B cells were activated by antigen-stimulated T blasts only in the presence of irradiated mononuclear cells autologous to the responding T blasts. The above responses seemed not to be regulated solely by the release of soluble factors; apparently cell to cell interactions had to take place to obtain an efficient B cell activation.

A micromethod for the induction and assay of specific in vitro antibody responses by human lymphocytes

Human lymphocytes obtained from peripheral blood or spleen were cultured with influenza virus in a microculture system to produce strain specific antibody which was detected by the enzyme linked immunosorbent assay (ELISA). Nanogram amounts of specific antibody could be detected in cultures of 4 x 10(5) cells.

Self-reactive T cells. IV. Self-reactive T cells induce polyclonal differentiation of IgM-producing B cells in vivo and in vitro

Intravenous injection of lymphoblasts (generated in vitro by different T- or B-specific mitogens) induced a polyclonal activation of IgM-producing B cells in vivo in the spleens of syngeneic recipient mice. This polyclonal differentiation of host-derived B cells to IgM-producing plaque-forming cells was stimulated by host-derived self-reactive T cells activated in the splenic lymphoid cell population in response to the syngeneic lymphoblast graft. We found a stable factor in the supernatants of cultures of proliferating self-reactive T cells that induced (antigen-independent) polyclonal maturation, but not proliferation of IgM-producing B cells.

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.

Self-reactive T cells. V. T cell-mediated suppression of B cell responsiveness to LPS

The intravenous injection of polyclonally activated lymphoblasts elicited a proliferative T cell reaction in the spleens of syngeneic recipient mice. In the non-fractionated cell populations obtained from these spleens 6 days after lymphoblast transfer, the LPS-induced proliferation and differentiation of B cells in vitro was suppressed. This suppressive effect was mediated by T cells, as i) treatment with anti-Thy-1 antiserum plus complement restored responsiveness of B cells to LPS in the spleen cell population that had responded in vivo to a syngeneic lymphoblast graft, and ii) the responsiveness of B cells to LPS was not impaired in non-fractionated spleen cell populations of nu/nu mice injected with syngeneic lymphoblasts. The relationship of this nonspecific T suppressor cell activity to the previously described non-specific T helper cell activity for B cell activation is discussed.

Dysfunctions of pokeweed mitogen-stimulated T and B lymphocyte responses induced by gammaglobulin therapy

Lymphocytes obtained from nonimmuno deficient children treated with commercially available preparations of gammaglobulin failed to proliferate and to mature into plasma cells in vitro after stimulation with pokeweed mitogen. The influence of the treatment on lymphocyte functions varied according to the cell population considered. A T helper cell activity was detected in these patients but only in the cell subset bearing receptors for IgG after irradiation. T lymphocytes exerted a suppressive effect that disappeared after irradiation or incubation at 37 degrees C. The suppressive cells were found among E rosette-forming cells depleted of leukocytes bearing receptors for IgG. Their suppressive effect was expressed only in the presence of normal radioresistant T lymphocytes that did not bear Fc receptors for IgG. Similar dysfunctions could be induced in vitro by incubation of normal T and B lymphocytes with gammaglobulin preparations. Because F(ab)'2 fragments or deaggregated preparations of gammaglobulin failed to activate T suppressor lymphocytes, this activation was likely triggered by attachment of Fc portion of denatured IgG to the corresponding membrane receptor. This activation step was prostaglandin E(2)-dependent, suggesting that activated monocytes were involved in the activation process. B lymphocyte responses appeared directly inhibited by attachment of denatured gammaglobulin on membrane Fc receptor. Our observations suggest that immunological effects of gammaglobulin therapy are not limited to antibody transfer, since it also induces subtle modifications of in vitro pokeweed mitogen-stimulated T and B cell responses. These modifications must be considered in interpreting results obtained in immunodeficient patients investigated under gamma-globulin therapy.

Histocompatibility requirements for T cell help in specific in vitro antibody responses to influenza virus by human blood lymphocytes

Specific antibody responses to influenza virus were obtained in vitro from human blood mononuclear cells (PBM). The response was T cell-dependent, as shown by separation of PBM into E rosette-positive (E+) and -negative (E-) populations. The histocompatibility requirements for T-B cells interactions in this response were analyzed by recombining E- and E+ fractions from donors with varying degrees of HLA compatibility. No antibody formation was obtained from any allogeneic combination except for the special case of HLA identical siblings. As these experiments included combinations with shared or identical HLA-DR specificities, it was unlikely that genetic restriction alone could account for the failure of T-B cell collaboration. Evidence that suppression was responsible for the lack of antibody formation was obtained from experiments in which allogeneic E+ cells profoundly depressed specific antibody responses of intact PBM. In contrast, no such suppression was seen in pokeweed mitogen-driven polyclonal Ig synthesis for which there are no major histocompatibility complex requirements for T cell help. The suppressor activity of allogeneic E+ cells was found to be radiation-sensitive. By irradiating E+ cells, it was, therefore, possible to test for T cell help across an HLA barrier without unwanted suppressor effects. Under these conditions, (irradiated) E+ cells were able to collaborate with allogeneic E- cells even with no HLA alleles in common. This was true even when autologous monocytes were depleted from the helper E+ population. Supernatants collected from antigen-driven cultures of allogeneic E- and E+ cells were able to replace helper T cells in the specific antibody response to influenza virus. The apparent lack of genetic restriction in these responses might, therefore, be explained by the production of a nonrestricted helper factor.

Immunoregulatory T-cell dysfunction in polyclonal gammopathy

The mechanisms responsible for the increased serum immunoglobulines in polyclonal gammopathy states are unknown. We have studied the regulation of peripheral blood B-cell immunoglobulin synthesis and secretion, by T cells of either blood or bone marrow compartments, in 20 patients with polyclonal gammopathy and 27 controls with normal serum immunoglobulin levels. When compared to B-T-cell cocultures of normals, cocultures of polyclonal gammopathy patients had significantly higher levels of immunoglobulin secretion (P less than 0.01). Normal T cells but not T cells from patients with polyclonal gammopathy suppressed B-cell immunoglobulin secretion (P less than 0.01) and not the number of cytoplasmic immunoglobulin-positive cells of the polyclonal gammopathy patients. T cells from patients with polyclonal gammopathy enhanced normal B-cell immunoglobulin secretion (P less than 0.05) but not the number of cytoplasmic immunoglobulin-positive cells. Controls' bone marrow T cells were more efficient than blood T cells in suppressing polyclonal gammopathy B cells (P less than 0.02). T cells in polyclonal gammopathy are predominantly helper cells and could play a role in the enhanced immunoglobulin secretion of B cells. Bone marrow T cells are more efficient than blood T cells in regulating B cells. It seems that T cells predominantly regulate B-cell immunoglobulin secretion and not the number of B cells with cytoplasmic Ig.

Short- and long-term effects of radiation on T-cell subsets in peripheral blood of patients with Hodgkin's disease

The present study was undertaken to determine the effect of radiotherapy on subpopulations of peripheral blood T cells from patients with Hodgkin's disease. T cell were purified from each specimen, and proportions and absolute numbers of T lymphocytes bearing receptors for the Fc portion of IgG (TG) and for Fc portion of IgM (TM) were enumerated by rosetting T cells with ox red blood cells (ORBC), which had been coated with anti-ORBC rabbit IgG or IgM, respectively. In untreated patients, the percentage of TG cells was significantly increased, and the percentage of TM cells was significantly decreased when compared with control values. In patients examined after radiotherapy, there was a severe depletion of total T lymphocytes. The percent and absolute values of TM cells were also markedly decreased in comparison with those found in either normal controls or untreated patients. In contrast, relative proportions of TG cells were significantly increased in the same treated patients, but the absolute numbers of these cells were essentially unchanged in comparison with those found before radiation therapy. There was a partial and progressive restoration of the number of TM lymphocytes some years after the treatment, but reduced percentages of TM lymphocytes and increased percentages of TG lymphocytes were still found in patients in continuous complete remission for at least five years or more. Similar alterations of the two T-cell subsets were also found in the peripheral blood of a small group of patients treated with radiation for testicular seminoma. These data clearly demonstrate that radiation therapy has a differential effect on identifiable and distinct subsets of cells in the human T-cell class.

Antigen-specific T-cell factors

Antigen-specific T-cell factors are mediator molecules which are produced by helper and suppressor T cells and which can perform the function of those cells in an antigen-specific manner. They probably play an important part in immunoregulation. The major histocompatibility complex has a controlling influence on their structure and activity, while their antigen-recognition properties may be conferred by immunoglobulin V regions. Interest in the factors derives from three related areas of research, namely (i) the problem of T-cell recognition of antigen; (ii) the mechanisms of cellular interactions in antibody production and cell-mediated immunity; and (iii) the genetic control of immune responses. This review discusses the literature up to June 1980 on their production, structure, genetic restriction and mechanism of action.

Suppressor activity of T cells bearing Fc receptors for IgG on lymphoid colony formation

Human T lymphocytes, upon phytohaemagglutinin stimulation, are able to form colonies in semisolid media. Peripheral T cell bearing Fc receptors (TG) were studied for their possible regulatory activity on lymphoid colony development. Although no substantial differences were observed between the cloning efficiency of unfractionated T cells (thus including TG cells) and T cells depleted of TG, a sharp suppression of colony formation occurred when positively selected TG cells were readded to TG-depleted suspensions. Therefore, TG suppressor activity seems to be strictly dependent upon cell interaction with ox IgG immune complexes used for TG cell isolation. Different experimental approaches failed to demonstrate, although did not exclude, that suppression in this system is mediated by soluble factors. gamma-irradiation of TG cells abrogated their suppressor capacity.

Histamine-binding suppressor T cells in rabbit peripheral blood

Peripheral blood leukocytes (PBL) from primed rabbits were able to suppress the in vitro anti-sheep red blood cell (SRBC) plaque-forming cell (PFC) response of autologous spleen cells. A population containing the suppressor cells could be isolated from PBL by cell fractionation on columns of insolubilized histamine. In contrast to spleen cells, PBL generatd a weak secondary anti-SRBC response in vitro. A strong response was obtained with PBL freed from histamine-binding (H+) cells. The addition of these H+ cells to cultures of H-PBL caused strong suppression. The H+ suppressor cell was further characterized as a radioresistant T cell. Low-dose irradiation of H- cells resulted in a supplementary enhanced PFC response suggesting that PBL also contain a radiosensitive regulator cell which is not histamine binding.

Blood lymphocyte subpopulations show characteristic changes during ACTH therapy in acute exacerbations of multiple sclerosis

The percentages of the various lymphocyte subpopulations in blood samples of 22 patients suffering from acute bouts of multiple sclerosis (MS) were determined by E rosette formation and peroxidase staining techniques, respectively, before and during ACTH therapy. In accordance with earlier reports, most of the subjects showed a normal increase of their plasma cortisol concentrations in an ACTH quick test, which was routinely performed before the beginning of therapy. We observed a significant transitory decrease of the absolute and relative T-cell proportions with a minimum around the tenth day of treatment, accompanied by inverse changes of the null-cell numbers. The concentrations of total white blood cells, total lymphocytes, B-cells, and monocytes did not change significantly. Our results are consistent with data reported in the literature on follow-up studies of lymphocyte subpopulations in patients with myasthenia gravis undergoing treatment with ACTH and corticosteroids, respectively. Recent experimental findings indicate that T-helper cell activity can be regulated by a negative feedback control mechanism. In consideration of these reports, we discuss the significance of changes in the distribution of lymphocyte subpopulations for the therapeutic action of ACTH and corticosteroids in MS.