With a recently introduced method for measurement of low-avidity anti-DNA, the polyethylene glycol (PEG) precipitation assay (Riley et al., 1979), high levels of DNA binding by normal human serum ...(NHS) were found when circular PM2-DNA was used as antigen. THe nature of this DNA binding was studied. The removal of low-density lipoproteins (LDL) from the serum, e.g., by Aerosil absorption, eliminated DNA binding by NHS. Purified LDL bound DNA to the same extent as NHS. Non-specific binding of NHS or LDL to DNA was prevented by adding dextran sulphate to the incubation mixture. Analysis on sucrose gradients showed that only large DNA-anti-DNA complexes were precipitated by 3.5% PEG. The PEG assay with dextran sulphate is a sensitive assay for low-avidity anti-DNA antibodies. It adds important information to results obtained with the Farr assay, which mainly detects antibodies of high avidity.
The proliferative response of purified malignant B cells from 26 patients with chronic lymphocytic leukemia (CLL) was investigated in vitro. In the majority of these patients, a proliferative ...response could be induced by the combination of tumor necrosis factor (TNF)- alpha and PMA. The concentration of PMA was found to be critical and showed a sharp optimum. In most cases maximal proliferation was obtained with as little as 0.1 ng/mL PMA. In all cases tested, TNF- alpha-induced proliferation could be inhibited completely by the addition of low doses of interleukin-4 (IL-4). Maximal inhibition was already found with 400 pg/mL IL-4. Inhibition by IL-4 was not caused by a downmodulation of TNF receptors. Apart from TNF-alpha, IL-2 was also in synergy with PMA able to induce proliferation in B-CLL cells of some patients. This IL-2-induced proliferation could be inhibited both by IL- 4 and by neutralizing anti-TNF-alpha antibodies. This shows that TNF- alpha also can act as an autocrine growth factor. These data indicate that TNF-alpha is an important growth factor for neoplastic B-CLL cells and that IL-4 provides a tool to interfere with this TNF-alpha response.
In this study, we investigated the pharmacokinetics of rituximab in patients with CD20 positive non-Hodgkin lymphoma, to get more insight into the factors that influence the pharmacokinetics of ...rituximab. This may aid to understand variability of treatment outcome, in patients with a CD20 positive malignancy treated with rituximab.
In this study, patients with a CD20 positive B-cell malignancy who were treated with rituximab containing regimens were included. Induction treatment schedules consisted of a combination of rituximab with chemotherapy for 4-8 cycles. Maintenance treatment consisted of a 2 or 3-monthly dose of 375 mg/m2 rituximab intravenously for 2 years. On the day of the treatment with rituximab, preinfusion blood samples were taken. Also, after the end of treatment, selected blood samples were taken. Rituximab levels were measured with a validated enzyme-linked immunosorbent assay (ELISA). An antigen binding assay was applied for determination of human-antibodies against chimeric-antibodies (HACAs).
Eight patients were on induction therapy. Rituximab levels of one patient on induction therapy remained very low after the first course. This patient had a chronic lymphoid leukemia with circulating tumor cells and a high tumor burden. Apart from one patient with mantle cell lymphoma, all patients on induction therapy had a complete response. Five patients were on maintenance therapy. Trough levels of 4 patients on three-monthly schedule maintenance therapy remained constant, with a median concentration of 6 mu g/mL (range 0.5-11.7 microg/mL). One patient had a relapse during his maintenance treatment. The elimination half-life at steady state of rituximab in all patients was estimated to be 19.2 (+/- 15.2%) days with a between-subject variability of 54%, indicating wide variability. Possible pharmacokinetic-pharmacodynamic relationship was observed as rituximab levels of the non-responders remained low compared to the rituximab levels of the responders. For all patients, concentration of HACAs remained below the quantification limit.
Considerable inter-individual variability of rituximab levels was observed. Although the patient population was small, the results support the need for more research into the pharmacokinetics and factors that might influence the pharmacokinetic-pharmacodynamic relationships of rituximab in patients with non-Hodgkin lymphoma.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We produced three murine monoclonal antibodies (mAb) directed against the human T-cell differentiation antigen CD2 (formerly T11) and analysed their epitope specificity by E-rosette inhibition, ...cross-blocking and proliferation-induction experiments. When added together, two mAb (both IgG1 kappa) were able to induce proliferation in peripheral blood T cells. This proliferation was found to be strictly dependent on the presence of monocytes. The polymorphism of Fc receptors (FcR) expressed on human monocytes for murine IgG1 antibodies, which is readily demonstrable in anti-CD3-induced T-cell activation, was not found in the anti-CD2-driven system. Moreover, mAb directed against the 40,000 MW FcRII were unable to inhibit proliferation induced by the mitogenic anti-CD2 combination. Still, F(ab')2 fragments of the mitogenic anti-CD2 antibody combination could not initiate T-cell mitogenesis, despite their ability to induce a rise in the free intracellular Ca2+. The contributions of monocytes and of antibody Fc moieties to T-cell proliferation, induced by combinations of anti-CD2 mAb, will be discussed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Most in vitro systems for the induction of IgE production by human B cells require both IL-4 and the presence of T cells. Little is known about the mechanism of T cell help or the ability of ...different T cell subsets to provide this helper activity. In the present study we demonstrate that, in the presence of exogenous IL-4, anti-CD3 stimulated naive T cells (CD4+CD45RA+) are potent helper cells for human IgE production. In their presence, as little as 750 autologous B cells can produce up to 100 ng/ml IgE. This response was found over a broad range of anti-CD3 concentrations. IgE helper activity by naive T cells was inhibited by IL-2. Under all conditions tested, naive T cells were unable to provide help for IgM production. This is in contrast to activated memory T cells (CD4+CD45RO+), which are very efficient helper cells for IgM or IgE production, provided that IL-2 or IL-2 plus IL-4 are present respectively.
Studies using an adapted immunofluorescence technique (IFT) on Crithidia luciliae to determine the complement fixing ability of antibodies to dsDNA in relation to disease manifestations, i.e., ...nephritis, have yielded conflicting results. To establish the relevance of these determinations, we studied sera containing antibodies to dsDNA from 64 patients with systemic lupus erythematosus (SLE), and found that anti-dsDNA of 52% of these sera had the ability to fix complement. SLE patients with nephritis demonstrated a much higher incidence of complement fixing anti-dsDNA (83%) than patients without nephritis (17%, p less than 0.01). On the other hand, patients with nephritis also had higher titers of anti-dsDNA (mean 1:400) than patients without nephritis (mean titer 1:75; p less than 0.01). A clearcut correlation between anti-dsDNA titer and complement fixing anti-dsDNA titer (p less than 0.01) was observed which obviously disturbs the correlation between nephritis and complement fixing anti-dsDNA. Comparing matched sera from patients with nephritis and patients without nephritis with the same antidsDNA titer, we found no difference in complement fixing anti-dsDNA. In the IFT used to measure complement fixing anti-dsDNA, incubation of the Crithidia slides with patients' serum was followed by an incubation with fresh normal serum which served as a source of complement. We observed that this incubation with fresh normal serum resulted in elution of anti-dsDNA antibodies from kinetoplast DNA. This elution was caused by IgG present in normal serum.
Studying the production of IL-6 by monocytes, endothelial cells and smooth muscle cells we observed that cytokine inducers like IL-1, TNF alpha, LPS, SAC and PMA could be divided roughly into two ...categories. One, that consisted of LPS and SAC, which had a potent IL-6 inducing effect on monocytes and minor or no effect on endothelial- and smooth muscle cells. The other category, consisting of IL-1, TNF alpha and PMA, induced IL-6 production in endothelial- and smooth muscle cells and of which IL-1 also induced IL-6 in monocytes. Only IL-1 induced IL-6 production in monocytes as well as in endothelial cells and smooth muscle cells. Besides IL-6, also IL-1 and TNF alpha were produced by monocytes however with different kinetics. None of the stimuli had any inhibitory effect on IL-6 production with the exception of PMA. Whereas PMA induced IL-6 production in endothelial cells and it potentiated the induction of IL-6 by IL-1 in these cells, it inhibited LPS-stimulated IL-6 production in monocytes. In line with the effects of PMA, staurosporin induced IL-6 production in monocytes and it inhibited IL-1 driven IL-6 production by endothelial cells.
In order to investigate variations in the microenvironment of oocytes within a cohort of maturing follicles the follicular volumes as well as the intrafollicular concentrations of oestradiol (E2) and ...progesterone (P) were measured in the golden hamster. At 10 h before ovulation the follicular volumes varied from 0.009 to 0.037 mm3 (mean +/- SD: 0.0187 +/- 0.0071 mm3; n = 36). Large follicles (greater than 0.025 mm3; n = 8) contained statistically significantly lower E2 and P levels (30.1 +/- 10.4 and 517 +/- 113 mumol/l, respectively) than the medium sized group (less than 0.025 and greater than 0.015 mm3; n =20): 46.9 +/- 16.0 (P less than 0.02) and 919 +/- 264 (P less than 0.0001) mumol/l, respectively. Small follicles (less than 0.015 mm3) showed the highest steroid levels: 97.0 +/- 33.3 and 1590 +/- 517 mumol/l for E2 and P (P less than 0.001 versus the medium sized group values). Correlation coefficients for the steroid concentrations and the follicular volumes appeared to be -0.674 for E2 and -0.612 for P (P less than 0.001). At the time studied a positive correlation between E2 and P concentrations in the follicles was found: r = 0.655 (P less than 0.001). The mean ratios of intrafollicular over serum steroid concentrations appeared to be approx 36 x 10(3) in the case of E2 and about 17 x 10(3) in the case of P. These results clearly show that there is an inverse relationship between follicular volume and intrafollicular steroid concentrations. The presence of a fine regulatory mechanism for a collective maturation of follicles is hypothesized.
The ability of Escherichia coli-derived lipopolysaccharide (LPS), recombinant (r) interleukin 1-beta (rIL-1 beta), and r murine tumor necrosis factor-alpha (rMuTNF-alpha) to induce interleukin 6 ...(IL-6) production in vivo was investigated. Peak serum IL-6 concentration was attained after 2 hr of LPS injection into mice. The coinjection of antiserum against rMuTNF-alpha with LPS resulted in a reduction of the induced serum IL-6 level, indicating the involvement of endogenous TNF-alpha in LPS induction of IL-6. Recombinant IL-1 beta and rMuTNF-alpha injected directly caused the production of substantial amounts of IL-6 within 30 min. The injection of a combination of rIL-1 beta and rTNF-alpha induced a significantly greater level of IL-6 than either agent alone. The greater level of serum IL-6 was associated with hypothermia and an increased lethality among mice injected with both cytokines. These data demonstrate the abilities of IL-1 beta and TNF-alpha to induce IL-6 production in vivo and indicate that LPS induction of IL-6 may be mediated, at least partially, through TNF-alpha action. The data describe a new in vivo biologic activity shared between IL-1 beta and TNF-alpha and suggest that IL-6 may be an important effector in the manifestation of TNF-alpha and IL-1 beta actions in vivo.
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