Refractory period phenomenon in the induction of tissue factor expression on endothelial cells

Tissue factor (TF) is the first factor of the extrinsic pathway of coagulation. Normally, TF is not expressed on the surface of endothelial cells. However, expression of TF can be induced in these cells in response to stimulation by diverse inflammatory mediators such as interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), lipopolysaccharide (LPS), and phorbol 12-myristate 13-acetate (PMA). We have studied the effect of these mediators on the kinetics of the induction of TF-related procoagulant activity (PCA) on human umbilical vein endothelial cells (HUVECs). PCA is transiently induced on HUVECs, attaining a peak some 4 to 8 hours after addition of inflammatory agents, with maximal accumulation of TF messenger RNA (mRNA) occurring 3 to 5 hours earlier. Because the expression of PCA by treated HUVECs returns to basal levels by 20 to 30 hours, we examined the response of these cells to a second inflammatory stimulus. Continuous incubation of cells with a single inflammatory agent for 24 to 48 hours induces a hyporesponsive state with respect to the reinduction of TF expression by the same agent (14% of the initial stimulation for IL-1 beta, 39% for TNF-alpha 30% for LPS, and 7% for PMA). Such a diminution in PCA was also observed in the levels of TF mRNA. By contrast, pretreatment of HUVECs with one agent did not dramatically affect the reinduction of TF by any of the three other factors. We subsequently focused our attention on the induction of the autologous refractory period by IL-1 beta. De novo protein synthesis was not required during the preincubation of ECs for hyporesponsiveness to be observed. The establishment of the refractory state did not depend on the downmodulation of IL-1 beta receptor affinity or expression. Moreover, pretreatment of HUVECs with IL-1 beta increased prostacyclin (PGI2) production in response to a second stimulation by IL-1 beta, although such cells were unable to reexpress TF under the same conditions. This result suggests that distinct secondary messenger pathways are involved in TF induction and PGI2 synthesis by IL-1 beta in HUVECs.

An HIV-1 and HIV-2 cross-reactive cytotoxic T-cell epitope

The HLA-B27-restricted HIV gag cytotoxic T-lymphocyte (CTL) epitope, 265-279, is highly conserved amongst HIV-1 isolates, only one, HIV-1ELI, having a single amino acid substitution. Over the same region HIV-2 differs by five amino acids. As a broadly cross-protective AIDS vaccine should protect against infection from all isolates of HIV-1 and HIV-2, we tested CTL specific for the HIV-1 265-279 epitope with peptide analogues from HIV-1ELI, HIV-2 and two simian immunodeficiency virus (SIV) isolates, and with recombinant vaccinia viruses expressing the respective gag genes, to determine whether there was any cross-reactivity for this CTL epitope. CTL from the HIV-1-infected donor could recognize the HIV-1ELI peptide, the HIV-2 peptide and recombinant vaccinia virus-infected target and one of the two SIV peptide-treated targets. Epitopes that exhibit such cross-reactivity may be valuable in vaccine design.

Pharmacokinetics of idarubicin after oral administration in elderly leukemic patients

We have studied the plasma pharmacokinetics of idarubicin (4-demethoxy daunorubicin) in 11 elderly patients suffering from acute myeloblastic leukemia receiving orally 30 mg/m2 per day for 3 consecutive days. Idarubicin culminated in plasma 4 hr after administration and followed three similar time courses after the three administrations. Idarubicinol (13-dihydro-4-demethoxy daunorubicin) was the only fluorescent metabolite in plasma and no aglycone could be detected; idarubicinol concentration was always higher than that of unchanged idarubicin. Due to its protracted half-life (64 hr in this study), this metabolite progressively accumulated and the ratio of the areas under the curve (0-24) idarubicinol/idarubicin increased from day to day. By comparison to results obtained after i.v. administration of the drug in another study, the bioavailability of idarubicin alone can be estimated to about 21%, whereas the bioavailability of the sum idarubicin + idarubicinol is about 41%.

Structural homologies between two HLA B27-restricted peptides suggest residues important for interaction with HLA B27

Recently we described an HLA B27-restricted peptide derived from HIV gag p24 protein. In this study we have isolated an HLA B27-restricted peptide from the nucleoprotein (NP) of influenza A virus. The shortest fragment recognized by cytotoxic T lymphocyte (CTL) is eight amino acids long, residues 384-391. Comparison of the sequence of these two HLA B27 restricted peptides reveals homologies which can be aligned from one peptide to the other. Of the eight residues, two are identical: tryptophan and isoleucine. Both peptides have a positively charged residue at the N terminus, lysine at position 265 of gag and arginine at position 384 of NP. Using modified peptides we have shown that lysine or arginine is crucial for the interaction with HLA B27. The wild-type gag peptide blocked CTL recognition of NP peptide by influenza-specific CTL, but removal of the lysine prevented inhibition of NP peptide recognition. The importance of these charged residues was confirmed by the observation that truncated NP and gag peptides where the lysine or arginine was removed were not recognized by specific CTL. Further studies showed that the tryptophan residue influenced the association of the gag peptide with HLA B27, because the affinity of the gag peptide for B27 was strongly increased after replacing this residue with a leucine or a tyrosine. However, these peptides were not recognized by gag-specific CTL, suggesting that the tryptophan may interact with both HLA B27 and T cell receptor. These observations should help in the identification of HLA B27-restricted peptides from other viruses or organisms.

CD44 contributes to T cell activation

We demonstrate here that the CD44 molecule, which mediates lymphocyte adhesion to high endothelial venules (HEV), is also involved in the delivery of an activation signal to the T cell. We have produced a CD44 mAb (H90) which is able to block the binding of lymphocytes to high endothelial venules. H90 had no effect on [3H]TdR incorporation of whole PBL stimulated by lectins, allogeneic cells, or CD3 mAb in the soluble phase; in contrast, it strongly increased [3H]TdR incorporation of PBL stimulated by CD2 pairs of mAb or by CD3 mAb linked to the plastic culture plates, when purified T cells were used, H90 mAb could efficiently induce them to proliferate after a primary signal of activation delivered via cross-linked CD3 or via CD2, an effect mediated by Il-2 synthesis and Il-2R expression. Thus, the effect of H90 mAb resembles the mitogenic effect of CD28 "9.3" mAb. However, several results show that CD28 and CD44 mediate different signals to the T cells: i) in contrast to CD28 mAb, CD44 mAb cannot complement the signal delivered by a soluble CD3 mAb, lectins, or PMA; ii) CD44 mAb, at the difference of CD28 mAb, cannot induce CD3+ thymocytes to proliferate in conjunction with a first signal provided via cross-linked CD3 or via CD2; iii) F(ab) fragments of H90 were efficient, whereas divalent fragments of CD29 9.3 mAb are required to produce activation signals; and iv) CD44 and CD28 mAb produce a very strong synergistic effect on T cell proliferation. These results fit with previous ones showing that endothelial cells can play the role of accessory cell in T cell activation and that a hierarchy of signaling can be delivered to T cells via CD3 and CD2.

CD44 contributes to T cell activation

We demonstrate here that the CD44 molecule, which mediates lymphocyte adhesion to high endothelial venules (HEV), is also involved in the delivery of an activation signal to the T cell. We have produced a CD44 mAb (H90) which is able to block the binding of lymphocytes to high endothelial venules. H90 had no effect on [3H]TdR incorporation of whole PBL stimulated by lectins, allogeneic cells, or CD3 mAb in the soluble phase; in contrast, it strongly increased [3H]TdR incorporation of PBL stimulated by CD2 pairs of mAb or by CD3 mAb linked to the plastic culture plates, when purified T cells were used, H90 mAb could efficiently induce them to proliferate after a primary signal of activation delivered via cross-linked CD3 or via CD2, an effect mediated by Il-2 synthesis and Il-2R expression. Thus, the effect of H90 mAb resembles the mitogenic effect of CD28 "9.3" mAb. However, several results show that CD28 and CD44 mediate different signals to the T cells: i) in contrast to CD28 mAb, CD44 mAb cannot complement the signal delivered by a soluble CD3 mAb, lectins, or PMA; ii) CD44 mAb, at the difference of CD28 mAb, cannot induce CD3+ thymocytes to proliferate in conjunction with a first signal provided via cross-linked CD3 or via CD2; iii) F(ab) fragments of H90 were efficient, whereas divalent fragments of CD29 9.3 mAb are required to produce activation signals; and iv) CD44 and CD28 mAb produce a very strong synergistic effect on T cell proliferation. These results fit with previous ones showing that endothelial cells can play the role of accessory cell in T cell activation and that a hierarchy of signaling can be delivered to T cells via CD3 and CD2.

Suppressor effects and cyclic AMP accumulation by the CD29 molecule of CD4+ lymphocytes

Integrins are a superfamily of related molecules whose function, where known, is to mediate adhesion. The so-called very-late-activation antigen (VLA) family includes at least five distinct heterodimers, each composed of a unique alpha-subunit non-covalently associated with a common beta-subunit. Several members of the family have been shown to bind extracellular matrix proteins, but the function of VLA-4 is so far unknown. VLA-4 is the only member of the family detected on thymocytes and resting T cells. We show here that an antibody which recognizes the beta-subunit of VLA-4 (CD29) on T cells can inhibit CD4+ cell proliferation triggered by CD2 or CD3, and that binding of this antibody to activated T cells leads to an increase in cyclic AMP levels which is comparable to that elicited by forskolin. These negative signalling effects are unique to this antibody: other CD29 antibodies do not affect the growth of activated CD4 cells but enhance the proliferation of whole T cell populations and abrogate the suppressive effects of mitomycin-treated CD8 cells on CD4-cell growth. Taken together, our results indicate that VLA-4 functions in cell-cell interactions and that it is the target for the suppressive effects of CD8 cells on CD4 cells.

A 19-kDa human erythrocyte molecule H19 is involved in rosettes, present on nucleated cells, and required for T cell activation. Comparison of the roles of H19 and LFA-3 molecules in T cell activation

We have previously described a molecule on the SRBC surface which, in addition to the sheep equivalent of LFA-3, is involved in the process of rosette formation. It is made of a single, 14- to 19-kDa, polypeptide chain, and we termed this molecule S14. We have now identified, on the human E a molecule with a similar Mr albeit somewhat higher (19 kDa). The mAb against H19 efficiently block autologous or homologous rosettes by binding to human E. In addition, purified H19 molecules block rosettes made with human E and SRBC in a dose-dependent manner. The H19 molecule, like LFA-3, is not limited to the E surface, but is also present on many nucleated cells, including T cells and monocytes. Moreover H19, like LFA-3, is required for T cell activation: when we stimulated whole PBMC anti-H19 blocked [H3]TdR incorporation triggered via CD3, but not via CD2, in contrast to anti-LFA-3 that inhibited activation via both pathways. When a mixture of highly purified T-PBL and autologous paraformaldehyde fixed accessory cells (AC) was cultivated, anti-H19 or anti-LFA-3 mAb bound to AC blocked T cell proliferation. When high amounts of rIL-1 (100 U/ml) were added to purified T-PBL, no AC were required to sustain their proliferation upon stimulation via CD2, contrary to stimulation via CD3. When lower amounts of rIL-1 (10 U/ml) were used, fixed AC were still necessary to sustain proliferation via CD2. In this latter situation, anti-H19 mAb bound to AC could no longer inhibit T cell proliferation, whereas the anti-LFA-3 mAb was still inhibitory. When T-PBL were stimulated via CD2 in the presence of 100 U/ml of rIL-1, anti-LFA-3 did not induce any inhibition. Thus the inhibitory effect of anti-H19 and anti-LFA-3 mAb can both be accounted for by an effect on the AC molecules only, and not on the T cell molecules. F(ab')2 fragments of anti-H19 mAb produced the same pattern of inhibition as the whole Ig molecule, excluding an effect via the FcR. Moreover, purified preparations of the H19 molecules also produced inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

A 19-kDa human erythrocyte molecule H19 is involved in rosettes, present on nucleated cells, and required for T cell activation. Comparison of the roles of H19 and LFA-3 molecules in T cell activation

We have previously described a molecule on the SRBC surface which, in addition to the sheep equivalent of LFA-3, is involved in the process of rosette formation. It is made of a single, 14- to 19-kDa, polypeptide chain, and we termed this molecule S14. We have now identified, on the human E a molecule with a similar Mr albeit somewhat higher (19 kDa). The mAb against H19 efficiently block autologous or homologous rosettes by binding to human E. In addition, purified H19 molecules block rosettes made with human E and SRBC in a dose-dependent manner. The H19 molecule, like LFA-3, is not limited to the E surface, but is also present on many nucleated cells, including T cells and monocytes. Moreover H19, like LFA-3, is required for T cell activation: when we stimulated whole PBMC anti-H19 blocked [H3]TdR incorporation triggered via CD3, but not via CD2, in contrast to anti-LFA-3 that inhibited activation via both pathways. When a mixture of highly purified T-PBL and autologous paraformaldehyde fixed accessory cells (AC) was cultivated, anti-H19 or anti-LFA-3 mAb bound to AC blocked T cell proliferation. When high amounts of rIL-1 (100 U/ml) were added to purified T-PBL, no AC were required to sustain their proliferation upon stimulation via CD2, contrary to stimulation via CD3. When lower amounts of rIL-1 (10 U/ml) were used, fixed AC were still necessary to sustain proliferation via CD2. In this latter situation, anti-H19 mAb bound to AC could no longer inhibit T cell proliferation, whereas the anti-LFA-3 mAb was still inhibitory. When T-PBL were stimulated via CD2 in the presence of 100 U/ml of rIL-1, anti-LFA-3 did not induce any inhibition. Thus the inhibitory effect of anti-H19 and anti-LFA-3 mAb can both be accounted for by an effect on the AC molecules only, and not on the T cell molecules. F(ab')2 fragments of anti-H19 mAb produced the same pattern of inhibition as the whole Ig molecule, excluding an effect via the FcR. Moreover, purified preparations of the H19 molecules also produced inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

Clinical and pharmacokinetic study of 96-h infusions of doxorubicin in advanced cancer patients

A phase I and a pharmacokinetic study of 96-h infusions of doxorubicin were performed in order to evaluate the maximum tolerated dose with this schedule of administration. Seventeen patients suffering from a digestive carcinoma were included in the study and a total of 71 courses of treatment were performed. The starting dose was 15 mg/m2/day and was increased in 2.5 mg/m2/day increments. The main toxicities observed were neutropenia and mucositis, which became limiting from 22.5 mg/m2/day (90 mg/m2 over a 96-h period); this dose was therefore defined as the maximal tolerated dose. No objective response to treatment was observed. For further studies, the recommended dose should not exceed 20 mg/m2/day. A plasma plateau concentration of doxorubicin was reached within 24 h. Despite a constant infusion rate, the plasma concentration of doxorubicin showed transient variations in several patients. However, an average plasma concentration could be evaluated for 33 courses of treatment, and this was linearly related to the dose. Doxorubicinol was the only detected metabolite of doxorubicin and its plasma concentration progressively increased throughout infusion. A detailed pharmacokinetic study was performed in 13 courses of treatment. The mean plasma clearance of doxorubicin was 25.2 l/h/m2 and the mean terminal half-lives of doxorubicin and doxorubicinol were respectively 43.6 and 66.2 h. Urinary excretion of doxorubicin plus metabolite was regular from the 24th to the 96th hour of infusion; however, the proportion of doxorubicinol progressively increased in urine. The protracted half-life of this metabolite probably explains its accumulation during infusion.

Differentiation of Burkitt lymphoma cells by hexamethylenbisacetamide

Hexamethylenbisacetamide (HMBA) can induce the Burkitt lymphoma Raji cells to enter the differentiation process as evidenced by the decrease of HLA-DR antigens. This event is preceded by a decrease of c-myc expression and of the phosphorylation of cellular proteins, due to either a decrease of tyrosine protein kinase activity or an increase of tyrosine phosphatase activity. These three events form a sequence and are part of the genetic program for differentiation and growth though they may not be causally related.

Comparison of signals delivered through CD3 and CD2 for T-cell activation: the role of calcium influx and interleukin 1

In the absence of monocytes, resting T lymphocytes extensively purified from human peripheral blood failed to proliferate when stimulated with a mixture of calcium ionophore, which elevates intracellular calcium levels, and TPA, which activated protein kinase C. A third signal, i.e., the triggering via CD3 or CD2 molecules, was necessary in order to observe proliferation. These highly purified T cells required the presence of monocytes in both CD3 and CD2 systems for their proliferation. Exogenous interleukin 1 clearly substituted for monocytes in CD2- but not in CD3- triggered T-cell proliferation. In contrast, the effect of CD2 and CD3 antibodies on Ca++ influx was apparently not dependent on the presence of monocytes. In the presence or absence of the monocytes, CD3, as well as certain combinations of CD2 monoclonal antibodies including the D66 monoclonal antibody, were able to increase the intracellular calcium concentration as measured by Quin 2 fluorescence. EGTA, a Ca++ chelator, completely inhibited CD2- and CD3- mediated T-cell proliferation, indicating that calcium uptake is necessary during the T-cell proliferation. The addition of TPA abrogated the inhibitory effect of EGTA and completely restored the response of the T cells stimulated by CD3, but not by CD2, monoclonal antibodies. In the CD2 pathway, EGTA-inhibited proliferation of T cells could be completely restored by addition of exogenous interleukin 2 as well as exogenous recombinant interleukin 1. Our results indicate that EGTA inhibits the production of interleukin 1 but has no direct effect on either interleukin 2 production or on Tac antigen expression. In this system, recombinant interleukin 1 alpha demonstrated a more potent ability for restoring the T-cell response than did recombinant interleukin 1 beta. These results suggest that interleukin 1 could act as a potent costimulatory factor in the non-antigen-specific T-cell activation.

The required interaction between monocytes and peripheral blood T lymphocytes (T-PBL) upon activation via CD2 or CD3. Role of HLA class I molecules from accessory cells and the differential response of T-PBL subsets

Previously, we have shown that paraformaldehyde-fixed monocytes are able to fully complement, in terms of [3H]dThd incorporation, a primary stimulus delivered to purified T cells by monoclonal antibodies (mAb) reacting with CD3 or CD2 molecules. Here, we show that depending on the stimulus used (CD3 mAb or different pairs of CD2 mAb) HLA class I molecules from monocytes are directly involved in complementary signals provided to T cells. This was evidenced by the following observations: (a) mAb reacting with the heavy or light chain of class I molecules, or their Fab fragments, completely blocked proliferation of peripheral blood lymphocytes (PBL) activated by CD3 mAb; (b) mAb against the heavy chain of HLA class I but not against beta 2-microglobulin partially blocked (approximately equal to 50%) PBL activation by the CD2 "GT2 + T111" mAb pair but did not block activation by CD2 "D66 + T111" mAb; (c) this pattern of inhibition was observed when anti-class I mAb were used in the soluble phase or when they were bound to monocytes subsequently fixed with paraformaldehyde and cultivated with purified autologous T cells; (d) fixed monocytes are able to restore interleukin (IL) 2 receptor expression on purified T cells stimulated by CD3 mAb or CD2 "GT2 + T111", contrary to anti-HLA class I mAb-pretreated monocytes. The inhibitory effects of anti-HLA class I mAb bound to monocytes were not found to be reversed by recombinant IL2 or recombinant IL1. We assume that HLA class I would be involved in two or more signals delivered to T cells by monocytes, the requirement in those signals depending on the initial stimulus applied to T cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics and metabolism of pirarubicin in advanced cancer patients

We have studied the pharmacokinetics and metabolism of pirarubicin (4'-O-tetrahydropyranyldoxorubicin) in six patients included in an EORTC phase II study. Pirarubicin was injected as an i.v. bolus of 5 min on 3 consecutive days at a dose of 20 mg/m2 per day. Blood samples were collected at regular times after each injection. Urine was collected over 12 h periods for 3 days and then over 24 h periods. Pirarubicin and metabolites were extracted on Sep-pak cartridges, and analyzed by HPLC with fluorometric detection. Unchanged pirarubicin followed three similar plasma concentration curves, which could be fitted by a two-compartment model with successive half-lives of 22.0 min and 12.7 h. Total plasma clearance of the drug was 90 l/h/m2 and total volume of distribution 1380 l/m2. Doxorubicin was the main metabolite in plasma after an injection of pirarubicin; its concentration was lower than that of pirarubicin but progressively increased from day to day and exceeded the level of pirarubicin 8 h after the 3rd injection of the drug until the end of the blood sampling. Pirarubicinol and doxorubicinol were also metabolites of pirarubicin in plasma; pirarubicinol followed similar plasma concentration curves during the 3 days of treatment whereas doxorubicinol progressively increased from day to day. Total urinary excretion represented about 6% of the dose injected. The same metabolites as in plasma were found in urine. Whereas the total amount of pirarubicin and pirarubicinol was the same in urine during the 24 h after each injection, the amounts of doxorubicin and doxorubicinol excreted increased from day to day, so that doxorubicin became progressively the main compound in urine after the end of the treatment. The progressive accumulation of pirarubicin metabolites (doxorubicin and doxorubicinol) after the repetitive injections of pirarubicin are probably due to the protracted half-lives of these compounds as compared to that of pirarubicin.

The reversal of doxorubicin resistance by verapamil is not due to an effect on calcium channels

Using a model of doxorubicin-resistant rat glioblastoma cells, we have studied the relationship between the reversal of multi-drug resistance by verapamil and calcium fluxes into the cells. Although it is known to be a voltage-dependent calcium channel blocker, verapamil exerted no effect on calcium entry into the cells. In the absence of calcium in the medium, drug resistance was not affected and verapamil was still active. It was possible to modify calcium fluxes into the cells by using manganese ions (decreasing calcium uptake) or the calcium ionophore A23187 (increasing calcium uptake). These agents had only a marginal effect on the expression of drug resistance by the cells and did not prevent the action of verapamil on its reversal.

Interleukin 2 up-regulates its own production

It has been previously reported that a combination pair of anti-CD2 monoclonal antibodies (mAb) T11(2)+T11(3) induces a strong proliferation of T cells, which does not require the involvement of accessory cells and exogenous interleukin 2 (IL-2). More recently, we have shown that the requirement for optimal T cell proliferation depends on the combination pairs of anti-CD2 mAb used. Among them, anti-GT2+T11(1) mAb do not allow optimal proliferation of TA4 helper cloned T cells due, at least in part, to a low level of IL-2 production. This observation offered us the opportunity to study the effect of IL-2 on its own production. We show here that stimulation of cloned TA4 cells with anti-GT2+T11(1) mAb induces only a marginal level of IL-2 production. By contrast, significantly higher levels of IL-2 activity are detected in the culture supernatant of TA4 cells preincubated with recombinant IL-2 (rIL-2) before stimulation with anti-GT2+T11(1) mAb. This effect is dose-dependent over a wide range (5 to 50 IU/ml) of rIL-2 concentrations added during preincubation time. In addition, it is not due to carryover of rIL-2 bound during the preincubation time, or to lesser IL-2 consumption by these cells, or to increasing numbers of IL-2-producing cells induced by exogenous IL-2. Moreover, the observation was confirmed with IL-2 mRNA. Although neither rIL-2 nor anti-GT2+T11(1) mAb alone could induce a significant production of IL-2, rIL-2 appears to up-regulate its own production when the TA4 cells are activated by the anti-CD2 mAb-mediated second signal.

Interleukin 2 up-regulates its own production

It has been previously reported that a combination pair of anti-CD2 monoclonal antibodies (mAb) T11(2)+T11(3) induces a strong proliferation of T cells, which does not require the involvement of accessory cells and exogenous interleukin 2 (IL-2). More recently, we have shown that the requirement for optimal T cell proliferation depends on the combination pairs of anti-CD2 mAb used. Among them, anti-GT2+T11(1) mAb do not allow optimal proliferation of TA4 helper cloned T cells due, at least in part, to a low level of IL-2 production. This observation offered us the opportunity to study the effect of IL-2 on its own production. We show here that stimulation of cloned TA4 cells with anti-GT2+T11(1) mAb induces only a marginal level of IL-2 production. By contrast, significantly higher levels of IL-2 activity are detected in the culture supernatant of TA4 cells preincubated with recombinant IL-2 (rIL-2) before stimulation with anti-GT2+T11(1) mAb. This effect is dose-dependent over a wide range (5 to 50 IU/ml) of rIL-2 concentrations added during preincubation time. In addition, it is not due to carryover of rIL-2 bound during the preincubation time, or to lesser IL-2 consumption by these cells, or to increasing numbers of IL-2-producing cells induced by exogenous IL-2. Moreover, the observation was confirmed with IL-2 mRNA. Although neither rIL-2 nor anti-GT2+T11(1) mAb alone could induce a significant production of IL-2, rIL-2 appears to up-regulate its own production when the TA4 cells are activated by the anti-CD2 mAb-mediated second signal.

Regulation of helper T cell clone proliferation via the CD2 molecule

We have investigated the requirements for CD2-induced proliferation of a CD4+, CD8-, CD3+, CD2+ antigen-specific, class II-restricted proliferating cloned cell line. A combination pair of two monoclonal antibodies (MoAb) recognizing, respectively, TII1 and D66 epitopes on the CD2 molecule was used as a stimulus. The regulatory function of accessory cells and various interleukins in this proliferation was determined. The results show that although this clone was able to proliferate in the absence of accessory cells (AC) or interleukin 1 (IL-1) when stimulated by these MoAb, AC constantly enhanced the response to these MoAb. AC acted by increasing high-affinity IL-2 receptor expression. On the contrary they did not play any role in IL-2 production. This regulation of IL-2 receptor expression by AC was specific of adherent cells, did not involve Fc receptors, was impaired when AC were metabolically inactivated and did not require T cell-AC interaction via LFA1, CD4, or HLA molecules. The AC function was not abrogated by anti-IL-1 antibodies and could not be replaced by exogenous IL-1. These results were compared to previously described AC effects on resting T-cell proliferation when stimulated with the same pair of anti-CD2 MoAb. Clear differences in activation requirements in resting and activated T cells via CD2 molecules were found.

Role in T-cell activation for HLA class I molecules from accessory cells: further distinction between activation signals delivered to T cells via CD2 and CD3 molecules

The immunological function of major histocompatibility complex molecules, including HLA class I molecules, is to present antigens and/or their processed peptides to various lymphocyte subpopulations. Thus, they play a pivotal role in regulatory interactions between cells of the immune system, which can result in the activation and function of T cells. We looked for a role of major histocompatibility complex molecules during T-cell activation induced by monoclonal antibody (mAb) or combinations of mAb recognizing the two well-characterized T-cell surface molecules CD3 and CD2. To activate T-cell peripheral blood lymphocytes, we used a CD3 mAb or two different pairs of CD2 mAb, CD2 "GT2 + T11(1)" and CD2 "D66 + T11(1)," which, as we have previously shown, deliver different signals of activation to T cells. Anti-HLA class I mAb blocked the activation induced by CD3 mAb or by CD2 GT2 + T11(1), but it did not block activation induced by CD2 D66 + T11(1). We observed this pattern of inhibition according to the stimulus used to activate T cells both when the anti-HLA class I mAbs were added to cultures of whole peripheral blood mononuclear cells and when they were fixed to monocytes only. In the latter case, purified monocytes were first incubated with the anti-HLA mAb (whether whole immunoglobulin or Fab fragment) and then fixed with paraformaldehyde before culture with autologous purified T cells. Anti-HLA class I fixed on monocytes prevented both interleukin 2 (IL-2) receptor expression and IL-2 synthesis on T cells. The inhibitory effects of anti-class I mAb bound to monocytes were not reversed by adding large amounts of recombinant IL-2 or recombinant IL-1, a finding consistent with the observations that accessory cells surface components can fully complement the signals directly delivered to T cells by CD2 or CD3 mAb. We conclude that HLA class I from accessory cells plays an important role in the early phase of T-cell activation when direct contacts between accessory cells and T cells are required.

Pharmacokinetics of idarubicin after daily intravenous administration in leukemic patients

We have studied the plasma pharmacokinetics of idarubicin (4-demethoxy-daunorubicin) in eight leukemia patients receiving five daily i.v. injections (7-9 mg/m2 per day) of this new anthracycline. For unchanged idarubicin, similar pharmacokinetic parameters were exhibited after the 1st and the 5th injection. Idarubicinol (13-dihydroidarubicin) was identified as the only detectable metabolite of idarubicin in plasma. Due to a protracted half-life (40 h) this compound progressively accumulated in plasma without the occurrence of peaks after the injections. This administration schedule provides therefore an interesting method of dose fractionation of a new anthracycline.

T cell activation via CD2 [T, gp50]: the role of accessory cells in activating resting T cells via CD2

Monoclonal antibody (MAb) GT2 defines a unique epitope on the CD2 molecule. GT2 triggers T cell mitosis in combination with any MAb directed against 9.6/T11(1) or D66, two previously defined CD2 epitopes. We have shown already that accessory cells (AC) are required for plenary T-PBL activation by any pair of Ab directed against D66 + 9.6/T11(1). In this study, we further investigated their role and found it to vary with the anti-CD2 pair used. When purified T-PBL preparation is used, the level of [3H]TdR incorporation observed with anti-(GT2 + 9.6/T11(1)) Ab was not significant; however, it did prove significant, although greatly reduced, with the other anti-CD2 pairs tested. This was due to qualitative differences in the process of T-PBL activation, and the role of AC, because: anti-(GT2 + 9.6/T11(1)) did not induce IL 2-R expression on purified T-PBL, whereas the other anti-CD2 pairs tested did; anti-(GT2 + 9.6/T11(1)) did not induce detectable IL 2 secretion from purified T-PBL, whereas the other anti-CD2 pairs tested induced a low amount; and anti-CDw18 Ab inhibited the mitogenic effect of anti-(GT2 + 9.6/T11(1)) on PBMC by preventing both IL 2-R expression and IL 2 secretion, whereas anti-CDw18 Ab enhanced the mitogenic effect of the other anti-CD2 pairs tested. Paraformaldehyde-fixed AC fully restored, and recombinant IL 1 partially restored purified T-PBL mitosis triggered by all anti-CD2 pairs tested. To induce IL 2 synthesis, the necessity to cross-link anti-CD2 Ab was demonstrated by coupling one Ab on Sepharose beads and adding the second Ab in the soluble phase: under these circumstances, anti-CD2 pairs were mitogenic solely in the presence of AC. These data can be interpreted as follows. Most anti-CD2 pairs require minimal contact between AC and T-PBL to induce plenary levels of IL 2 synthesis. When anti-(GT2 + 9.6/T11(1)) are used, additional contact is necessary, both for IL 2-R expression and IL 2 synthesis, which would include CDw18 for stabilization. We believe these differences could be related to different conformational changes on the CD2 molecule, depending on the epitope on which the antibodies bind, and could account for different signaling to T cells.

T cell activation via CD2 [T, gp50]: the role of accessory cells in activating resting T cells via CD2

Monoclonal antibody (MAb) GT2 defines a unique epitope on the CD2 molecule. GT2 triggers T cell mitosis in combination with any MAb directed against 9.6/T11(1) or D66, two previously defined CD2 epitopes. We have shown already that accessory cells (AC) are required for plenary T-PBL activation by any pair of Ab directed against D66 + 9.6/T11(1). In this study, we further investigated their role and found it to vary with the anti-CD2 pair used. When purified T-PBL preparation is used, the level of [3H]TdR incorporation observed with anti-(GT2 + 9.6/T11(1)) Ab was not significant; however, it did prove significant, although greatly reduced, with the other anti-CD2 pairs tested. This was due to qualitative differences in the process of T-PBL activation, and the role of AC, because: anti-(GT2 + 9.6/T11(1)) did not induce IL 2-R expression on purified T-PBL, whereas the other anti-CD2 pairs tested did; anti-(GT2 + 9.6/T11(1)) did not induce detectable IL 2 secretion from purified T-PBL, whereas the other anti-CD2 pairs tested induced a low amount; and anti-CDw18 Ab inhibited the mitogenic effect of anti-(GT2 + 9.6/T11(1)) on PBMC by preventing both IL 2-R expression and IL 2 secretion, whereas anti-CDw18 Ab enhanced the mitogenic effect of the other anti-CD2 pairs tested. Paraformaldehyde-fixed AC fully restored, and recombinant IL 1 partially restored purified T-PBL mitosis triggered by all anti-CD2 pairs tested. To induce IL 2 synthesis, the necessity to cross-link anti-CD2 Ab was demonstrated by coupling one Ab on Sepharose beads and adding the second Ab in the soluble phase: under these circumstances, anti-CD2 pairs were mitogenic solely in the presence of AC. These data can be interpreted as follows. Most anti-CD2 pairs require minimal contact between AC and T-PBL to induce plenary levels of IL 2 synthesis. When anti-(GT2 + 9.6/T11(1)) are used, additional contact is necessary, both for IL 2-R expression and IL 2 synthesis, which would include CDw18 for stabilization. We believe these differences could be related to different conformational changes on the CD2 molecule, depending on the epitope on which the antibodies bind, and could account for different signaling to T cells.

Regulation of immunoglobulin synthesis by human T cell subsets as defined by anti-D44 monoclonal antibody within the CD4+ and CD8+ subpopulations

In our previous paper, we demonstrated that anti-D44 MAb can, in the presence of complement, eliminate all the allocytotoxicity generated during a mixed lymphocyte reaction without affecting the alloproliferative response. As approximately 70% of CD4+ cells and 30% of CD8+ will be stained with anti-D44 MAb, we researched the functional role of the D44+ and D44- cells in each of these T cell subsets in the PWM-induced antibody response. We found that most of the helper activity for immunoglobulin (Ig) synthesis was mediated by CD4+ D44+ lymphocytes and that virtually all the suppressive activity was mediated by CD8+ D44- lymphocytes. Surprisingly enough, we noticed that the low level of Ig synthesis induced in B cells by CD4+ D44- lymphocytes could be strongly amplified by the addition of radiosensitive CD8+ lymphocytes, suggesting coexisting opposite immunoregulatory functions within the CD8+ T cell subset. These results, together with previous data, indicate that anti-D44 MAb subdivides T cells into subpopulations with distinct functional repertoires: a CD4+ D44+ helper subpopulation, a CD8+ D44+ cytotoxic subpopulation, and a CD8+ D44- suppressor subpopulation.

Regulation of immunoglobulin synthesis by human T cell subsets as defined by anti-D44 monoclonal antibody within the CD4+ and CD8+ subpopulations

In our previous paper, we demonstrated that anti-D44 MAb can, in the presence of complement, eliminate all the allocytotoxicity generated during a mixed lymphocyte reaction without affecting the alloproliferative response. As approximately 70% of CD4+ cells and 30% of CD8+ will be stained with anti-D44 MAb, we researched the functional role of the D44+ and D44- cells in each of these T cell subsets in the PWM-induced antibody response. We found that most of the helper activity for immunoglobulin (Ig) synthesis was mediated by CD4+ D44+ lymphocytes and that virtually all the suppressive activity was mediated by CD8+ D44- lymphocytes. Surprisingly enough, we noticed that the low level of Ig synthesis induced in B cells by CD4+ D44- lymphocytes could be strongly amplified by the addition of radiosensitive CD8+ lymphocytes, suggesting coexisting opposite immunoregulatory functions within the CD8+ T cell subset. These results, together with previous data, indicate that anti-D44 MAb subdivides T cells into subpopulations with distinct functional repertoires: a CD4+ D44+ helper subpopulation, a CD8+ D44+ cytotoxic subpopulation, and a CD8+ D44- suppressor subpopulation.