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The antigen-induced DNA synthesis in vitro in lymphocytes from patients with acute Plasmodium falciparum malaria was investigated. The patients and healthy controls from Sweden or Colombia were the same as those studied in the accompanying paper (Troye-Blomberg el al., 1983). The malarial antigens used were sonicated membrane preparations or purified and concentrated supernatants from in vitro cultures of P. facliparum, similar preparations derived from normal human erythrocytes served as control antigen. In the patients' lymphocytes P. falciparum antigens induced a weak or moderate but significant stimulation of DNA synthesis, peaking after 3-4 days of incubation. This early response was specific for P. faleiparum since it was not obtained with lymphocytes from healthy donors nor with those from patients with acute P. vivax or P. ovale malaria. No antigen-induced response was seen in about half of the P.falciparum patients. However in a few negative eases, available for consecutive testing, positive reactions were seen with lymphocytes taken 2 weeks after infection when the blood of these patients was free of parasites. The early response induced in patients' lymphocytes to the P. falciparum antigens was not obtained with RBC antigen, however, these preparations frequently induced a response rising to significant levels later during incubation (day 5-6)- Similar delayed responses were obtained when either- patients' or control donors' lymphocytes were exposed to the P. falciparum antigens. This indicates that both the RBC and the parasite preparations contained mitogenic substances affecting human lymphocytes in general and easily obscuring the P, falciparum specific responses seen only in the patients. This latter response was relatively low and short lived, suggesting that it reflected a secondary in vitro stimulation of in vivo primed lymphocytes and that it was regulated by suppressor mechanisms. [ABSTRACT FROM AUTHOR]

Lack of serum IgG2, IgA and IgE was found in a healthy male adult blood donor. No secretory IgA could be demonstrated. In vitro activation of lymphocytes did not induce IgA secreting cells although no class specific suppressor cells could be found. Normal or slightly subnormal titres to a variety of bacterial and viral antigens were demonstrated whereas anti-carbohydrate antibodies (anti-teichoic acid, anti-dextran and anti-pneumococcal polysaccharide) were virtually absent. Isoagglutinins and heteroagglutinins were present in somewhat lower concentrations than normal. [ABSTRACT FROM AUTHOR]

Nearly two billion people are latently infected with Mtb (LTBI). Detection of LTBI with high risk to develop active tuberculosis (aTB) is considered the cornerstone to control the disease. The current challenge is to identify markers that better classify LTBI versus aTB. It has been previously shown that Rv0140, a reactivation‐associated antigen of Mtb, induces significantly higher IFN‐γ production in LTBI individuals as compared to aTB patients. Herein, we show that Rv0140 induces high granzyme B level by PBMCs derived from LTBI (n = 34) as compared to aTB (n = 18). Receiving operator characteristic (ROC) curves were used to evaluate the capacity of Rv0140 to discriminate between LTBI and aTB by measuring IFN‐γ and granzyme B secretion. Our results show that, in response to Rv0140, granzyme B seems to allow better discrimination of LTBI from aTB with areas under the curve (AUC) of 0.88 (95% CI 0.79–0.98) as compared to IFN‐γ with AUC of 0.85 (95% CI 0.74–0.96) even though CI overlap. Intracellular staining (ICS) experiments and the use of anti‐MHC I antibody showed that granzyme B is mainly produced by CD8+ T cells in response to Rv0140. Thus, we propose granzyme B as a host marker to help identify LTBI individuals. Rv0140‐induced Granzyme B biomarker discriminates TB infection status [ABSTRACT FROM AUTHOR]

Affinity maturation of antibodies during immune responses is achieved by multiple rounds of somatic hypermutation and subsequent preferential selection of those B cells that express B cell receptors with improved binding characteristics for the antigen. The mechanism underlying B cell selection has not yet been defined. By employing an agent-based model, we show that for physiologically reasonable parameter values affinity maturation can be driven by competition for neither binding sites nor antigen--even in the presence of competing secreted antibodies. Within the tested mechanisms, only clonal competition for T cell help or a refractory time for the interaction of centrocytes with follicular dendritic cells is found to enable affinity maturation while generating the experimentally observed germinal centre characteristics and tolerating large variations in the initial antigen density. [ABSTRACT FROM AUTHOR]

We studied T cell responses to four glutathione S transferase (GST)-fused mite antigens prepared in our laboratory using peripheral blood lymphocytes from mite-sensitive patients with bronchial asthma. Of the four recombinant antigens, purified GST-Mag3 had the strongest ability to cause patients' lymphocytes to proliferate, and its potency was almost comparable to that of crude mite bodies (Dfb) and faeces (Dff) antigens and a purified major antigen, Der f 2. The responder lymphocytes were mainly T cells, because the proliferative response was depleted by the treatment of lymphocytes with anti-CD3 antibody and complement, but not with anti-CD20 antibody and complement. The responsiveness of lymphocytes to GST-Mag3 correlated with that to Der f 2, but GST-Mag3 displayed slightly higher activity to stimulate lymphocytes than Der f 2. Simultaneously, the levels of Dff- and GST-Mag3- specific IgE antibodies correlated with the responsiveness of lymphocytes to GST-Mag3. These results suggest that Mag3 is a new valuable antigen for the response of T cell proliferation in mite-sensitive patients. [ABSTRACT FROM AUTHOR]

This study pertains to classification and antigenic analysis of mycobacterial plasma membrane proteins in relation to human T cell proliferative responses, using a 'fast grower' Mycobacterium fortuitum as model. Membrane vesicles, prepared by sonication and differential centrifugation, were subjected to biphasic Triton X-114 extraction for isolation of integral (detergent phase) and peripheral (aqueous phase) proteins. Neither protein pool showed any appreciable overlap serologically. SDS-PAGE showed five prominent bands in peripheral and three in the integral protein pool, whereas immunoblotting with rabbit antisera identified only two major antigens (60 and 67 kD) in the former and five (24. 34, 42, 51 and 54 kD) in the latter, ELISA with a panel of anti-mycobacterial MoAbs revealed that nine out of 2 previously known antigens were present in the peripheral protein pool. Only two of them (33 and 40 kD) were additionally detected amongst integral proteins. The membrane-associated immunosuppressive moiety lipoarabinomannan was semiquantitatively located in aqueous phase. In bulk T cell proliferation assays, seven out of 10 subjects belonging to a 'responder" background (BT-BB leprosy patients and healthy contacts) showed high responses for Myco. foruiitum antigens. Proliferative response with integral proteins was comparable to that with whole membrane, but it was significantly higher (P < 0.0005) than the response with peripheral proteins. The distinction and relevance of integral membrane proteins as a class of mycobacterial antigens make them worthy of consideration in a subunit vaccine design. [ABSTRACT FROM AUTHOR]

The T cell response to different Leishmania donovani antigens was investigated using peripheral blood mononuclear cells (PBMC) from Kenyans cured of visceral leishmaniasis and non-exposed Danes. Crude promastigote and amastigote antigens both induced proliferation and interferon-gamma (IFN-γ) production in PBMC from cured patients, while cells from non-exposed donors gave weak responses. A similar pattern was induced by lipophosphoglycan-associated protein (LPGAP). By contrast, the major surface protease of Leishmania, gp63, induced only a weak proliferative response without IFN-γ production in five of 17 samples from cured patients. Four of the five responding cultures produced IL-4, i.e. the response to this antigen was of the Th2 type. Furthermore, sera from acutely ill visceral leishmaniasis patients contained high levels of IgG antibodies to gp63. The Th2-like response to gp63 in patients cured of visceral leishmaniasis differs from the Th1-like response to the same antigen observed in patients cured of cutaneous leishmaniasis. [ABSTRACT FROM AUTHOR]

A wide spectrum of different immunologic abnormalities have been postulated as being responsible for the impairment of specific antibody production and the decrease in all or selected immunoglobulin isotypes present in common variable immunodeficiency (CVID). These abnormalities include impaired B cell differentiation and/or function, defective macrophage function, and significant T cell defects. The aim of the present study was to delineate whether the accessory molecule CD28 is involved in the impaired antigen response of T cells from patients with CVID. Our results demonstrate that CD28 costimulation was functional in T cells stimulated with anti-CD3 or anti-TCR MoAb, but could not correct the impaired response of patients' peripheral blood T cells to tetanus toxoid. Analysis of patients' long-term cultured T cells further confirmed these results. Exogenous rIL-2, another costimulus, augmented but did not correct the defective proliferation and lymphokine production in patients' antigen-driven peripheral blood T lymphocytes or in long-term cultured T cells. These findings indicate that the CD28 signalling pathway in these patients' T cells is unimpaired, and that costimulation via C'D28 cannot correct the defect occurring in the course of TCR-mediated T cell activation. [ABSTRACT FROM AUTHOR]

Children living in hyperendemic malarious regions have high immunoglobulin levels and an increased frequency of Burkitt's lymphoma. In a study of Gambian children which endeavours to explain these findings we showed that acute P. falciparum malaria caused spontaneous activation and growth of their B lymphocytes in vitro. A high proportion of these cells contained Epstein Barr nuclear antigen (EBNA). In ancillary experiments aimed at explaining these findings. CD4 helper cells from adult donors were destroyed with monoclonal antibody and complement. This manoeuvre resulted in loss of cytotoxic T cell control of their B lymphocytes when infected with Epstein Barr virus (EBV). In children with acute malaria., both spontaneous immunoglobulin and antibody production by B cells was increased yet CD4 helper cell control over these cells, as measured by responses to pokeweed mitogen, was found to be intact. Spontaneous and concanavalin A-driven lymphocyte proliferation was depressed. We infer from these findings that in patients with P. falciparum malaria loss of cytotoxic T cell control of the EBV in B cells, possibly due to destruction or dysfunction of a subset of CD4 cells responsible for induction ot suppressor/cytotoxic CD8 cells, leads to activation and proliferation of foci of B cells containing EBV. The expanded pool and rapid turnover of these cells may increase chances of malignant transformation leading to the genesis of Burkitt's tumor. Partial loss of suppressor mechanisms coupled with normal CD4 helper/inducer activity may result in high serum levels of immunoglobulin which are characteristic of persons living in malarious regions. [ABSTRACT FROM AUTHOR]

When Meth-A fibrosarcoma-bearing BALB/c mice were injected subcutaneously with 10 µg of recombinant human interleukin 2 (rIL-2) once a day for 10 days, tumour growth inhibition was in the range of 22-31% of that of the control animals. Anti-tumour effector cells against Meth-A were detected in the spleen cells of the tumour-bearing BALB/c mice injected with rIL-2, using a modified Winn-type neutralization assay with the auxiliary injection of rIL-2. To induce the strongest anti-tumour activity in this assay system, the following were necessary: 1) the effector cells were derived from tumour-bearing BALB/c mice; 2) the donors of the effector cells were injected with rIL-2:3) the recipient mice in the Winn assay were auxiliarily injected with rIL-2 (a modified Winn assay). The anti-tumour effector activity detected in the modified Winn assay was inhibited by treatment with anti-CD8 or anti-asialo GM1 antibodies plus complement (C), but not completely. We supposed that at least two kinds of anti-Meth-A effector cells with different surface antigens, positive for CD8 and asiato GM1 antigens, were induced in the Meth-A-bearing BALB/c mice injected with rIL-2; these populations seemed to function independently and at least partly as anti-tumour effector cells in this tumour-host system. These spleen cells showed in vitro cytoloxicity against Meth-A cells, which are resistant to NK cells, if the activity was measured inn 24 h 51Cr-release assay in the presence of rIL-2. [ABSTRACT FROM AUTHOR]

The effect of interleukin 2 (IL-2) on cord blood mononuclear cells (CBMC) was studied, with special reference to B cell function. The study shows that CBMCs proliferate in response to recombinant interleukin 2 (rIL-2) without in-vitro preactivation. The response was also detected when whole blood cultures were used. CBMCs not preactivated in vitro proliferated in response to rIL-2 even after T cell and monocyte depletion. Thus, rIL-2 affects both non-T cells and T cells of newborns without preactivation in vitro. IL-2 receptors on unstimulated CBMCs appear to be distinct from Tac antigen, as the mean number of Tac antigen-positive cells among CBMCs was only 0.8%. Furthermore, rIL-2 inhibited PWM-induced proliferation and the response was more prominent in newborns than in adults. Thus, rIL-2 seems to cause a higher increase of suppressor cell function in CBMCs than in adult peripheral blood mononuclear cells. Neither rIL-2 nor Staphylococcus aureus Cowan 1 (SAC) stimulated any IgM synthesis, but a dose-dependent IgM synthesis was obtained by combining SAC and rIL-2. Alone, however, rIL-2 appears to be an insufficient factor to induce differentiation of SAC-activated cord blood B cells, as no IgM production in response to rIL-2 occurred in T cell and monocyte-depleted cell populations. The results of this study suggest both increased suppressor cell function and intrinsic B cell deficiency as causes of a weak humoral immune response in newborns. [ABSTRACT FROM AUTHOR]

In the burn patient, the mechanisms leading to impaired T lymphocyte activity are unclear. The capacity for T cell proliferation and the expression of Tac antigen (IL-2 receptor) was assessed during the post-burn period in patients with injuries ranging from 5-68%, total body surface area. T cell-dependent (polyclonal) immunoglobulin synthesis, mixed lymphocyte reaction and Interleukin-2 production were also determined in these patients and correlated with survival. Surviving patients demonstrated a transient reduction while terminal patients exhibited a permanent reduction in the number of Tac lymphocytes, unrelated to the absolute number of T cells, during the post-burn period. The reduced percentage of lL-2 receptor-expressing T cells coincided with the suppressed antibody response and reduced alloreactivity. Although the concentration of IL -2 was decreased in all patients throughout the hospitalization period, surviving patients showed a gradual increase in its production while terminal patients gradually decreased to undetectable levels. Exogenous recombinant IL-2 induced a significant enhancement of in-vitro polyclonal immunoglobulin production and blastogenesis in the mixed lymphocyte reaction in immunosuppressed patients who demonstrated up to 50%, reduction in the percentage of IL-2 receptor positive cells. Thus, the reduced capacity for production of and response to lL-2 alter thermal injury may lead to the immunosuppression due to a lack of T lymphocyte clonal expansion. The permanent nature of this detect in patients who died from fatal sepsis may suggest a causative relationship. [ABSTRACT FROM AUTHOR]

We studied mitogen- and antigen-induced interleukin 2 (IL-2) production in HTLV-Ill LAV infected and non-infected individuals and compared the results with T cell subpopulations. and with mitogen- and antigen-induced DNA synthesis and production of leucocyte migration inhibitory factor (LIF in order to understand the controversial findings related to IL-2 production in HTLV-III/V infection. The HTLV-llI/LAV antibody positive group showed immunologial defects: low T helper (Th) cells, high Th- suppressor (Th) cells, reduced mitogen- and antigen-induced DNA-synthesis. but LIE production comparable to the HTLV-lll/LAV antibody negative group. The total amount of IL-2, produced either as a response to a mitogenic stimulus or as a response to a soluble antigenic (purified protein derivative of tuberculin, PPD) stimulus, was lower in the HTLV-III/LAV antibody positive group. However, adjusting the IL-2 production to the amount of Th-cells showed that the IL-2 produced by a standard number of Th-cells after mitogen induction was similar in HTLV-lll/LAV infected and non-infected individuals. In contrast, the ability of Th-cells of infected persons to produce IL-I or to proliferate as a response to a soluble antigenic stimulus, was considerably diminished. We conclude that HTLV-lll infection leads to a selective incapability to mount a specific Th- cell response either due to an intrinsic defect in the Th-cell population or due to metabolic and/or functional disturbances in antigen-processing and presenting accessory cells. [ABSTRACT FROM AUTHOR]

CBA/Ca mice were infected by either the intravenous or intraperitoneal route with Mycobacterium microti and the subsequent changes in local macrophage populations examined. Following infection, the number of macrophages increased and they showed greater expression of both MHC Class II molecules. This response was not dependent on viability of the mycobacteria, in contrast to reports with other microorganisms such as Listeria. Studies in sublethally irradiated mice indicated that persistent antigen could give rise to a response after a period of host recovery which was radiation dose dependent. This procedure also highlighted differences in the regulation of different murine class II antigens in vivo as seen by delayed re-expression of I-E antigens. Macrophage accessory cell function, as assessed by an in vitro T cell proliferation assay, correlated with la expression after fixation, but not after indomethacin treatment; this highlights the diverse nature of regulatory molecules produced by these cells. [ABSTRACT FROM AUTHOR]

Addition of 40 μM 2'deoxyguanosine (2'd Guo) results in enhancement of human lymphocyte cultures stimulated with pokeweed mitogen. assessed by staining intracytoplasmic immunoglobulins. Furthermore, B cell responses were enhanced under experimental conditions favouring T cell suppression rather than help. Experiments with enriched B cell fractions indicate that 2'dGuo does not directly stimulate B cell responses. The enhancement by 2'dGuo was still observed in the presence of irradiated (non-proliferating) T cells. The mechanism of enhancement by 2'dGuo is discussed in terms of its effect on proliferation-independent suppressor T cells. [ABSTRACT FROM AUTHOR]

Interactions of human T cells and macrophages/monocytes (MØs) following stimulation by a Gram negative micro-organism (E. coli) have been investigated. Immunoadsorption studies showed that the E. coli-induced proliferative response of human T cells was antigen specific. The T cell pool could be selectively depleted of E. coli reactive cells by short exposure to autologous E. coli pulsed Møs, This treatment did not remove T cell reactivity directed towards an unrelated antigen (tetanus toxoid). This demonstrated the antigen specificity of the immunoadsorption step, which was further confirmed by reconstitution of E. coli reactivity after supplementing the adsorbed T cell pool with E. coli specific T cells. The MØ requirement for the E. coli-induced T cell response was confirmed and kinetic studies showed a dose-dependence with respect to the amount of E. coli used for both E. coli-induced T cell proliferation and the efficiency of immunoadsorption. [ABSTRACT FROM AUTHOR]

Human thymus and T cell antigens were identified by using four distinct monoclonal antibodies (MoAb). designated 2D5, 5B3, 7A5 and 9D4, 2D5 antibody reacted with most human thymocytes and a few peripheral Lymphocytes as well as with a subpopulation (20%) of bone marrow cells, and precipitated a 45K molecular weight (mol. wt.) component from 125I-labelled thymus cell lysate. 7A5 antibody also reacted with the majority (80%) of thymocytes but neither with peripheral lymphocytes nor with bone marrow cells. The antigen detected by 7A5 was a glycoprotein consisting of 48K and 12K mol. wt. components, which were non-covalently associated with each other. 5B3 reacted with virtually all of human thymus and T cells but not with the majority of B cells and bone marrow cells. This reagent precipitated a 72K mol. wt. glycoprotein from thymus and T cells. An additional 65K mol. wt. glycoprotein was precipitated by 5B3 together with the 72K mol. wt. component, but with poor reproducibility. 9D4 antibody, on the other hand, reacted with a 200K mol. wt. component from thymus and T cells as well as 220K and 2JOK components from the non-T cell fraction of tonsil lymphocytes. Whereas antigens detected by 2D5 and 7A5 appeared to be highly expressed on cortical thymocytes, the antigen defined by 5B3 occurred much more abundantly on medullary thymocytes and peripheral I cells than on cortical thymocytes. Based on the data described above, it is suggested that 7A5, 5B3 and 9D4 MoAb recognize human homologues of mouse TL. Ly-1 and Ly-5 antigens, respectively, whereas 2D5 antibody seems to resemble OKT10, as described by others. [ABSTRACT FROM AUTHOR]

The relationship between the expression of T3 and T6 antigens and the capacity lo respond to phytohaemagglutinin (PHA) has been studied in the lymphocyte component of nine human thymomas. It appears that there is a positive correlation between the mitogen responsiveness of thymoma lymphocytes and the relative proportion of T3 positive (T3+),T6 negative (T6- ), peanut receptor negative and IgM-Fc receptor positive cells. Moreover we have comparatively investigated the dexamethasone (Dex) inhibitory effect on the mitogenesis of T lymphocytes from thymoma, normal thymus and peripheral blood. In the presence of the macrophage product interleukin 1, the capacity of Dex to inhibit the mitogenesis of peripheral blood purified T cells (PBT) is inversely correlated with the PHA concentration used. Conversely. Dex completely (>90%) inhibits thymocyte mitogenesis irrespective of PHA concentration. The entity of Dex inhibitory effect on thymoma lymphocyte mitogenesis shows a great variability ranging between that observed in normal thymocytes and that observed in PBT. In each thymoma case the degree of inhibition appears to be dependent on the size of the more mature thymocyte pool being positively correlated with the number of T6+ but negatively with that of T3+ cells. Our data demonstrate a high degree of variability among thymomas relative to the phenotypic and functional properties of their lymphocyte component. On the other hand, in some thymomas the phenotypic and functional characteristics of lymphocyte component seem to represent only a narrow span of normal thymocyte maturative pathway. In this respect, human thymoma may constitute a profitable tool for studying the intrathymic T lymphocyte maturative steps. [ABSTRACT FROM AUTHOR]

Peripheral blood mononuclear cells from atopic donors were stimulated in vitro with allergens (Rye group I or Dermatophagoides pteronyssinus). T cell lines were originated and maintained in long term culture using lL-2 and periodical restimulations with allergen. The lines were antigen specific (i.e. responded to the allergen used to raise them and not to other antigens) and required that the antigen was presented by autologous cells (i.e. they were restricted). The restriction elements were probably at the level of HLA-DR antigens since the proliferative response was specifically blocked by anti-HLA-DR antibodies. Surface marker analysis revealed that the lines comprised mainly cells with an helper/inducer phenotype, although cells with markers of the suppressor/cytotoxic T cells were also present. The lines could be cloned by limiting dilution and clones with the same restriction and specificity as the parental line were isolated. These studies demonstrate the possibility of obtaining a large number of allergen specific human T cells that can be used for further in vitro studies on the regulation of the IgE response. [ABSTRACT FROM AUTHOR]

Purified B lymphocytes obtained from human tonsil cell populations by removing; E. rosette-forming cells by density sedimentation did not proliferate at three days in response to PHA and Con A, but showed a significant ³H-labelled thymidine incorporation when the PHA response was assessed at day 6 of culture. The 6th-day response, which was completely abolished by the reduction of T-cell contamination to less than 0-1% by re-rosetting and a second separation, was due in part to a direct activation by PHA of contaminating T cells and in part to a T cell-mediated B-cell response. When purified B cells were stimulated for 3 days by PHA in the presence of an equal number of autologous or homologous mitomycin-treated T lymphocytes a highly significant uptake of ³H-labelled thymidine was demonstrated. The majority of List cells obtained at day 4 in these cultures were unable to form E rosettes and showed surface immunoglobulin by immuno-fluorescence stain. This response was markedly decreased by previous treatment of B cells with mitomycin C and it was abolished when B cells were killed by heating at 56°C for 1 hr. Purified B lymphocytes from human tonsils did not respond in vitro when cultured for 6 days in the presence of soluble antigens (PPD and Candida). However, a highly significant response to the same antigens could be demonstrated when B cells were cultured in the presence of autologous mitomycin-treated T cells. These models of T-B co-operation could provide an interesting tool for studying the differentiation and antibody production in vitro of human B lymphocytes. [ABSTRACT FROM AUTHOR]