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(1/430) Suppression of lymphocyte transformation by plasma from owl monkeys acutely infected with Plasmodium falciparum.

Plasma collected from owl monkeys during the acute phase of Plasmodium falciparum infection was shown to adversely affect several in vitro responses which are considered to be correlates of cell-mediated immune functions of normal monkeys. In the presence of acute-phase plasma, response of normal monkey peripheral blood lymphocytes to stimulation with phytohemagglutinin, concanavalin A, and pokeweed mitogen was severely reduced, as was the ability of peripheral blood lymphocytes to respond to allogenic and xenogenic histocompatible antigens. The transformation response of peripheral blood lymphocytes from normal humans to phytohemagglutinin and concanavalin A was also suppressed. Since acute-phase plasma was not cytotoxic for peripheral blood lymphocytes, decreased responsiveness did not result from cell destruction. Acute-phase plasma appears to block initial steps in lymphocyte transformation.  (+info)

(2/430) Mitogen-induced proliferation increases biotin uptake into human peripheral blood mononuclear cells.

We sought to determine whether the proliferation of immune cells affects the cellular uptake of the vitamin biotin. Peripheral blood mononuclear cells (PBMC) were isolated from healthy adults. The proliferation of PBMC was induced by either pokeweed lectin, concanavalin A, or phytohemagglutinin. When the medium contained a physiological concentration of [3H]biotin, nonproliferating PBMC accumulated 406 +/- 201 amol [3H]biotin. 10(6) cells-1. 30 min-1. For proliferating PBMC, [3H]biotin uptake increased to between 330 and 722% of nonproliferating values. Maximal transport rates of [3H]biotin in proliferating PBMC were also about four times greater than those in nonproliferating PBMC, suggesting that proliferation was associated with an increase in the number of biotin transporters on the PBMC membrane. The biotin affinities and specificities of the transporter for proliferating and nonproliferating PBMC were similar, providing evidence that the same transporter mediates biotin uptake in both states. [14C]urea uptake values for proliferating and nonproliferating PBMC were similar, suggesting that the increased [3H]biotin uptake was not caused by a global upregulation of transporters during proliferation. We conclude that PBMC proliferation increases the cellular accumulation of biotin.  (+info)

(3/430) Comparison of enterovirus-specific cellular immunity in two populations of young children vaccinated with inactivated or live poliovirus vaccines.

Enterovirus-specific cellular immunity was studied in Estonian and in Finnish children at the age of 9 months. The aim was to evaluate the level of responsiveness in two neighbouring countries with different poliovirus immunization practices and striking differences in the incidence of insulin-dependent diabetes mellitus (IDDM), a disease in which early enterovirus infections are an aetiological risk factor. The Estonian children immunized with live attenuated polio vaccine had stronger T cell responses to coxsackievirus B4 and poliovirus type 1 when compared with Finnish children immunized with inactivated polio vaccine (median stimulation indices 10.4 and 6.3 in Estonian children and 1.9 and 2.9 in Finnish children, respectively; P < 0.05). Lymphocytes stimulated by poliovirus type 1 antigen expressed interferon-gamma (IFN-gamma) mRNAs, which strongly correlated with the level of proliferation responses. Lymphocytes of Estonian children had a tendency towards stronger expression of IFN-gamma upon poliovirus challenge when compared with Finnish children. The number of children who had experienced coxsackievirus B infections, as determined by the presence of neutralizing antibodies, did not differ between Estonian and Finnish children. The results show that Finnish children have weaker cellular immunity against enteroviruses at the age of 9 months compared with Estonian children at the same age. This is most probably due to the difference in polio vaccination schedules; in Estonia live poliovirus vaccine is used and given at earlier ages than the inactivated vaccines in Finland. This leads to stronger T cell immunity which cross-reacts with other enterovirus serotypes. This may explain the lower incidence of IDDM in Estonia by providing effective protection against diabetogenic enterovirus strains in Estonian children.  (+info)

(4/430) Enhanced B cell survival in familial macroglobulinaemia is associated with increased expression of Bcl-2.

A family with three cases of macroglobulinaemia of undetermined significance (MGUS), and one case each of immunoblastic lymphoma, Waldentrom's macroglobulinaemia and multiple myeloma was first described 20 years ago. We have previously identified 10 out of 35 healthy family members tested whose lymphocytes produced abnormally high amounts of immunoglobulins in culture. In the present study lymphocyte subpopulations of these hyper-responders have been further characterized and lymphocyte reactivity and survival in vitro have been studied. No differences were detected in the proportions of resting B lymphocytes (CD19+) co-expressing CD5, CD10, CD11b, or CD38, and the CD4/CD8 ratio of T cells was normal before and after stimulation with pokeweed mitogen (PWM). The initial rate of response in terms of immunoglobulin production was not increased, but immunoglobulin levels continued to rise during the second week of culture whereas the production peaked at 8 days in control cultures. This was associated with significantly greater survival of lymphocytes and at 14 days surviving B cells could only be identified in samples from hyper-responders. A lymph node removed because of tuberculosis from a family member 23 years before the diagnosis of multiple myeloma showed very marked Bcl-2 expression in a B cell follicle. This was not seen in a tuberculous lymph node from an unrelated subject. Stimulated cultures from three hyper-responders tested demonstrated significantly higher retention of Bcl-2 in B cells compared with one family control and six unrelated controls. We conclude that the increased production of immunoglobulins previously observed in this family with an inherited tendency for benign and malignant B cell proliferation is the result of enhanced B cell survival, which is associated with increased expression of Bcl-2 following stimulation.  (+info)

(5/430) Stimulation of human B lymphocytes by Listeria cell wall fraction.

Cell wall fraction of Listeria monocytogenes (LCWF), a B cell mitogen for mouse spleen cells, is also mitogenic for human adult and cord peripheral blood lymphocytes. Purified B-cell suspensions responded to LCWF in vitro proliferation, to a similar extent as the unfractionated suspensions. Furthermore, LCWF-induced B cell differentiation into IgM-containing cells and their percentage correlated significantly with the extent of lymphocyte proliferation.  (+info)

(6/430) Activated self-MHC-reactive T cells have the cytokine phenotype of Th3/T regulatory cell 1 T cells.

In the present study, we show that human self-MHC-reactive (autoreactive) T cell clones are functionally distinct from Ag-specific T cell clones. Self-MHC-reactive T cells exhibited helper function for B cell Ig production when cultured with non-T cells alone, and they exhibit suppressor function when cultured with PWM- or rCD40 ligand (rCD40L)-activated non-T cells, whereas tetanus toxoid (TT)-specific clones exhibited only helper function in the presence of TT with or without PWM or rCD40L. Addition of neutralizing Abs to the cultures showed that the suppression was mediated by TGF-beta but not by IL-10 or IFN-gamma. The self-MHC-reactive clones also inhibited proliferation of primary CD4+ T cells and TT-specific T cell clones, but in this case the inhibition was mediated by both IL-10 and TGF-beta. In further studies, the interactions between self-MHC-reactive T cell clones and non-T cells that led to suppressor cytokine production have been explored. We found that prestimulation of non-T cells for 8 h with PWM or for 48 h for rCD40L results in non-T cells capable of inducing self-MHC-reactive T cell to produce high levels of TGF-beta and IL-10. In addition, these prestimulation times coincided with peak induction of HLA-DR and costimulatory B7 molecule (especially CD86) expression on B cells. Finally, addition of CTLA-4/Fc or blocking F(ab')2 anti-CTLA-4 mAb, plus optimally stimulated non-T cells, to cultures of self-MHC-reactive clones inhibited the induction of TGF-beta but not IL-10 or IFN-gamma production. In summary, these studies show that activated self-MHC-reactive T cells have the cytokine phenotype of Th3 or T regulatory cell 1 and thus may be important regulatory cells that mediate oral and peripheral tolerance and prevent the development of autoimmunity.  (+info)

(7/430) CD9 expression enhances the susceptibility of myeloma cell lines to cell-mediated cytolysis.

Myeloma tumor cells, both freshly excised and cultured, are extremely resistant to cell-mediated cytolysis. As evidence suggests that B-cell susceptibility to lysis is dependent upon its state of differentiation and activation, we tested the ability of a variety of B-cell proliferation and differentiation agents, including pokeweed mitogen (PWM), to enhance the sensitivity of myeloma cells to cell-mediated lysis. PWM was found to significantly enhance the susceptibility of myeloma cell lines and freshly isolated myeloma cells to interleukin-2 (IL-2)-activated cell-mediated cytolysis. This effect was seen with the use of both IL-2-stimulated natural killer (NK) cells and T cells as effectors. The enhanced sensitivity of myeloma cells to cytolysis correlated with an increase in their cell surface expression of CD9, a pre-B cell marker and member of the transmembrane 4 superfamily. Incubation of PWM-stimulated myeloma cells with either monoclonal antibodies or antisense oligonucleotides directed against CD9 abrogated the effect of PWM. In order to determine whether there was a direct relationship between the expression of CD9 and enhanced sensitivity to cytolysis, myeloma cell lines that lacked CD9 expression were transfected with the CD9 gene. The level of cell surface CD9 expression correlates with enhanced susceptibility to lysis. Therefore, CD9 appears to be an important component in enhancing the sensitivity of myeloma cells to lysis mediated by IL-2-activated T cells and NK cells.  (+info)

(8/430) Shipment impairs lymphocyte proliferative responses to microbial antigens.

Lymphocyte proliferation assays (LPAs) are widely used to assess T-lymphocyte function of patients with human immunodeficiency virus infection and other primary and secondary immunodeficiency disorders. Since these assays require expertise not readily available at all clinical sites, specimens may be shipped to central labs for testing. We conducted a large multicenter study to evaluate the effects of shipping on assay performance and found significant loss of LPA activity. This may lead to erroneous results for individual subjects and introduce bias into multicenter trials.  (+info)