Interleukin 2 receptor expression by human blood lymphocytes after vaccination with pneumococcal polysaccharides.

Proliferative responses of unseparated peripheral blood mononuclear cells (PBMC) and blood T cells to recombinant interleukin 2 (rIL-2) were significantly increased 7-21 days after the vaccination with pneumococcal polysaccharides (PPS). In contrast, non-T cells expressed increased responsiveness to rIL-2 only on post-vaccination day 7. Analysis of the proliferative response to rIL-2 among lymphocyte subsets (CD4+Leu8+, CD4+Leu8-, CD8+Leu8+, CD8+Leu8-, CD20+) in cultures of unseparated PBMC revealed that the CD8+Leu8- T cells expressed increased responsiveness 7-14 days after vaccination, whereas neither CD4+ (Leu8+ and Leu8-) nor CD8+Leu8+ T cells showed significantly increased responsiveness after vaccination. The CD20+ B cells, like non-T cells, expressed increased responsiveness to rIL-27 days after the vaccination only. Expression of the 55 kD low-affinity interleukin 2 receptor (IL-2R, CD 25) on freshly isolated PBMC, as judged by direct fluorescence staining with a MoAb anti-55 kD chain, was low (less than 3%) and an increased expression of this receptor was not detected following vaccination. In contrast, binding of 125I-labelled IL-2 to freshly isolated PBMC increased following vaccination (day 7). Scatchard plot analysis revealed a modest increase in the expression of high-affinity IL-2R (Kd = 1-2 pM), whereas the increase in expression of the 75-kD, intermediate-affinity IL-2R (Kd = 300 pM) was more pronounced (from 195 to 295 (means) receptors per PBMC). It is concluded that, following vaccination with PPS increased IL-2R expression is induced on blood lymphocytes. These investigations suggest a role for T cells in the human immune response against PPS.     

Recombinant interleukin 2 inhibits pokeweed mitogen-induced proliferation of human adult peripheral blood and cord blood mononuclear cells

We studied the effects of recombinant interleukin 2 (rIL-2) on pokeweed mitogen (PWM)-induced proliferation of unfractionated human mononuclear cells from the peripheral blood (PBMCs) and cord blood (CBMCs). rIL-2 was found to inhibit PWM-induced proliferation of both PBMCs and CBMCs in a dose-dependent manner. The response was statistically significant at concentration 10 U/ml. The inhibition of adult PBMC proliferation was relatively mild, but in newborns up to 75% inhibition was found. The inhibitory effect of rIL-2 was best detectable at day 4, at the same time as PWM-induced proliferation peaked. However, also at days 8 and 10, the response induced by PWM plus rIL-2 was much lower than that induced by rIL-2 alone. These finding suggest that the inhibition was due to rIL-2-mediated stimulation of the function of PWM-activated suppressor cells. CD8+ T cells were, however, not alone responsible for the rIL-2-induced inhibition of PWM-induced proliferation, since the responses were essentially similar independent of whether CD8+ T cells were present or absent. In addition, the release of interferon-gamma (IFN-gamma) in response to rIL-2 was not a major cause of the inhibitory effects, because rIL-2 inhibited PWM-induced proliferation of CBMCs, which are deficient in producing IFN-gamma. Our results provide novel data to the ongoing discussion of IL-2 as a down-regulator of immune functions.     

T lymphocyte anergy during acute infectious mononucleosis is restricted to the clonotypic receptor activation pathway.

The transient T cell anergy associated with acute infectious mononucleosis (IM) caused by the Epstein-Barr virus has been analysed in a sample of 14 IM children. Peripheral blood mononuclear cells (PBMC) obtained from IM patients showed a significant specific impairment in their proliferative response to both phytohaemagglutinin (PHA; P less than 0.05) and to an anti-CD3 MoAb (P less than 0.001), although both responses reached normal control levels by addition of a submitogenic dose of either phorbol myristate acetate (PMA) or recombinant IL-2 (rIL-2). In contrast, activation signals delivered through other surface molecules (CD2, CD28) or other transmembrane pathways (PMA plus a calcium ionophore) elicited normal or high proliferative responses in most IM PBMC. In a group of five patients tested, the synthesis of IL-2 by IM PBMC in the presence of PMA was impaired when PHA or anti-CD3 was used as stimulus, but it reached normal levels with anti-CD2 or ionophore. Lastly, PHA failed to induce IL-2 alpha receptor (IL-2R alpha) expression in IM PBMC from four tested patients, but the presence of PMA completely corrected this defect. Taken together, these results strongly suggest that the T cell anergy associated with acute IM is due to a T cell receptor (TCR)-specific impairment in the induction of genes involved in T cell proliferation (including those coding for IL-2 and IL-2R alpha) upon membrane signalling to otherwise normal T lymphocytes, since CD2, CD28 and certain transmembrane activation pathways are uncoupled from CD3 in these particular pathological conditions (and perhaps in most in vivo situations). This and other similar experimental approaches to transient secondary immunodeficiencies may help to unravel the physiopathological role of different surface molecules in T cell activation.     

The role of monocytes in IL-3 enhancement of human T cell proliferation

We have assessed the role of recombinant human interleukin 3 (rIL-3) in the activation and proliferation of peripheral blood lymphocytes (PBL) and their various subsets. rIL-3 significantly enhanced the CD2-responsiveness of unfractionated PBL. Proliferating cells were mainly T lymphocytes and most of them expressed CD4. This effect was absent following adherent cell depletion from PBL. rIL-3 also failed to directly activate purified lymphocytes, nor did it increase T cell responsiveness to mitogens and/or IL-2. By contrast, rIL-3 induced monocyte functions as enhancement of IL-1 production was observed following treatment of these cells by rIL-3. This effect was removed by anti IL-3 mAb addition to these cultures. In addition, anti IL-1 antibody partially inhibits IL-3-derived responses. Together, these data strongly suggest that IL-3 stimulation of T lymphocytes is related mainly to its ability to enhance monocyte functions.     

Induction of Th2 cell differentiation in the primary immune response: dendritic cells isolated from adherent cell culture treated with IL-10 prime naive CD4+ T cells to secrete IL-4

A number of observations indicate that exposure to IL-4 is essential for the priming of Th2-type effector T cells and that exposure to IL-12 is essential for the priming of Th1-type effector T cells. However, the initial source of IL-4 in the early immune response has not been clearly identified. Dendritic cells (DC) are the most potent antigen- presenting cells (APC) in priming naive T cells. In this report, we show that DC exposed to IL-10 may play an important role in the priming of IL-4-secreting cells in the early immune response. DC isolated from splenic adherent cell cultures treated with rIL-10 (IL-10-DC) primed naive ovalbumin (OVA)-TCR transgenic T cells to secrete IL-4 upon re- stimulation with OVA and splenic APC. By contrast, DC isolated from rIL- 12, rIL-4 or control treated cultures induced almost exclusively Th1- type effector T cells. IL-4 secretion was detected in the primary cultures of IL-10-DC plus naive CD4+ T cells and the priming of IL-4- secreting T cells by IL-10-DC was dependent on endogenous IL-4 production in the priming culture since anti-IL-4 neutralizing antibody completely abrogated the priming of IL-4-secreting cells. Anti-B7-2 but not anti-B7-1 inhibited the ability of IL-10-DC to prime T cells to secrete IL-4. Furthermore, the ability of IL-10 DC to prime for IL-4- secreting T cells was closely related to the down-regulation of CD40 ligand-mediated IL-12 p70 production by DC in the primary cultures and was markedly reduced by adding exogenous IL-12 to the priming cultures. Thus, our findings indicate that early immunologic events that drive Th2 differentiation involve the effects of IL-10 on DC.      

Simian immunodeficiency viruses with defective nef genes show increased susceptibility to the noncytotoxic antiviral activity of CD8+ lymphocytes

The noncytotoxic soluble factor produced by CD8+ T cells inhibits replication of HIV and SIV in vitro and is thought to play a crucial role in combatting infection in vivo. We determined the effect of human CD8+ lymphocytes on the in vitro replication potential of both wild-type and nef-defective mutants of the simian immunodeficiency virus SIVmac251. Although replication of wild-type SIVmac251 in unstimulated human PBMC supplemented with IL-2 was unaffected by the presence of CD8+ T cells, the nef mutants were susceptible to the inhibitory effects. The effect of exogenous IL-2 depended upon the culture conditions: (i) in nonstimulated human PBMC depleted of CD8+ T cells, addition of IL-2 had a positive effect on the growth of the nef-defective viruses; (ii) in total human PBMC, IL-2 appeared to reinforce the CD8+ T-cell-dependent inhibition of the same mutant viruses. This strongly suggests that IL-2 stimulates the noncytotoxic anti-HIV/SIV response of CD8+ cells present in PBMC cultures. PHA stimulation of unfractionated human PBMC overrode the suppression of viral replication by CD8+ T cells. Depletion of activated T cells expressing the IL-2 receptor alpha-chain (CD25+ T cells), present in small amounts in these primary T cell cultures, dramatically reduced viral replication, indicating that the depleted cell population harbors the target cells permissive for viral replication. Furthermore, using neutralizing antibodies we could show that inhibition by the beta-chemokines MIP-1alpha, MIP-1beta, and RANTES and the inhibitory effect of CD8+ lymphocytes on nef mutant SIVmac viruses are harbored on different levels.     

1,25-Dihydroxyvitamin-D3 regulation of interleukin-2 and interleukin-2 receptor levels and gene expression in human T cells

1,25-Dihydroxyvitamin-D3 (1,25-D3) is known to inhibit DNA synthesis, immunoglobulin and lymphokine production [interleukin-2 (IL-2), gamma interferon (G-IFN), and granulocyte-monocyte colony-stimulating factor (GM-CSF)] by mitogen-stimulated human peripheral blood mononuclear cells (PBMCs). Recent data suggest these inhibitory effects are mediated at the gene level through inhibition of mRNA accumulation of specific lymphokines in the activated cells. In previous studies, we have demonstrated the CD8+ T cell population was less sensitive to the anti-proliferative actions of 1,25-D3 than CD4+ T cells. The purpose of this investigation was to further assess ability of 1,25-D3 to regulate CD4+ and CD8+ T cell functions. Initial experiments showed that 1,25-D3 inhibited both IL-2 production and mRNA accumulation in mitogen-stimulated PBMC. However, IL-2 receptor (IL-2R) expression and mRNA accumulation in stimulated PBMC was not affected by 1,25-D3. Both FACS sorted CD4+ and CD8+ T cells expressed IL-2R equally upon stimulation and neither showed an inhibitory effect on this expression by 1,25-D3. Human CD4+ and CD8+ T cells showed a stimulus-specific production of IL-2. CD4+ cells stimulated with mitogen and HLA-DR positive accessory cells produced measurable levels of IL-2 that were completely inhibited by 1,25-D3. CD8+ T cells did not generate measurable amounts of IL-2 in this system. However, CD4+ and CD8+ T cells produced large amounts of IL-2 when stimulated with mitogen and a protein kinase C activator, phorbol myristate acetate (PMA). Under these circumstances, both CD4+ and CD8+ T cell IL-2 production was inhibited completely by 1,25-D3. These data suggest that IL-2R expression in PBMCs and T cell subsets is equal and unaffected by 1,25-D3 while IL-2 production in T cell subsets is stimulus-specific and completely inhibited by 1,25-D3.     

High recombinant interleukin-2 sensitivity of peripheral blood lymphocytes from patients with myasthenia gravis: correlations with clinical parameters

Myasthenia Gravis (MG) is an autoimmune disorder of neuromuscular transmission associated with antibodies (Ab) against acetylcholine receptor (AChR). Autoantibody production is a T-cell-dependent phenomenon perhaps caused by aberrant immunoregulation. So far, a possible role for immunoregulatory molecules has not been investigated in the pathogenesis of MG. Since interleukin-2 (IL-2) is able to induce peripheral blood mononuclear cell (PBMC) proliferation without a previous activating signal and to upregulate IL-2-receptor expression, we have evaluated the activation state of PBMC in patients with MG, by cytofluorographic analysis of CD25 expression and by testing their sensitivity to recombinant IL-2 (rIL-2) without any known previous stimulation. We found no significant difference in CD25 expression in a large group of patients compared to controls. However, proliferative responses to rIL-2 were significantly higher in MG patients than in controls. In MG, as in controls, this response was time- and dose-dependent, was inhibited by an anti-IL-2 receptor Ab and correlated with an increased percentage of CD25+ T cells after rIL-2 exposure. The response was greater in patients with a high anti-AChR Ab titer and a severe form of the disease, and in patients tested before thymectomy. Thus blood T cells in MG showed functional signs of preactivation (high sensitivity to rIL-2 alone) without detectable CD25 expression on fresh cells, raising the possibility of aberrant IL-2 receptor regulation and/or expression in MG T cells. Decreased sensitivity to rIL-2 after thymectomy, associated with general clinical improvement, suggests a role for activated cells originating from the thymus in the pathogenesis of MG, and is of clinical relevance in patient follow-up. Our findings also provide a new approach in the study of MG pathogenesis: the search for aberrant immunoregulation mechanisms linked to defects in lymphokine circuits.     

Deregulated cytokine network and defective Th1 immune response in multiple myeloma

Intracellular cytokine production by peripheral blood mononuclear cells (PBMC) was analysed in 51 patients with multiple myeloma (MM), 22 with monoclonal gammopathy of undetermined significance (MGUS) and 20 healthy subjects, as a parameter of immunological dysfunction in MM. An increased proportion of T cells and HLA-DR+ cells producing IL-6 was observed in MM patients with active disease (at diagnosis and relapsing) compared with patients in remission and with MGUS, whereas no difference of IFN-gamma+, IL-2+ PBMC between patients and controls was evident. Determination of serum cytokine levels demonstrated that the imbalanced IL-6 production by T cells and the defective anti-tumour Th1 cell activity were related to elevated levels of IL-6 and IL-12. In vitro studies of PHA- and anti-CD3/anti-CD28 MoAbs stimulation of PBMC demonstrated the ability of lymphocytes from MM patients to differentiate towards the Th1 subset in the presence of rIL-12. By contrast, addition of exogenous rIL-6 impaired IFN-gamma production by rIL-12-prompted T cells. Inhibition of Th1 polarization of the immune response by IL-6 was direct on T cells and not mediated by dendritic cells (DC). Evaluation of the ability of MM-derived DC to stimulate cell proliferation of allogenic T lymphocytes and produce IL-12 in vitro, in fact, suggested that MM-derived DC were functionally active. Taken as a whole, these results indicate that a deregulated cytokine network occurs in active MM. They also suggest that increased IL-6 production by peripheral T lymphocytes contributes to the immune dysfunction observed in MM, and enables tumour cells to escape immune surveillance by preventing the anti-tumour Th1 immune response.     

DNA activates human immune cells through a CpG sequence-dependent manner.

While bacterial DNA and cytosine-guanosine-dinucleotide-containing oligonucleotides (CpG ODN) are well described activators of murine immune cells, their effect on human cells is inconclusive. We investigated their properties on human peripheral blood mononuclear cells (PBMC) and subsets thereof, such as purified monocytes, T and B cells. Here we demonstrate that bacterial DNA and CpG ODN induce proliferation of B cells, while other subpopulations, such as monocytes and T cells, did not proliferate. PBMC mixed cell cultures, as well as purified monocytes, produced interleukin-6 (IL-6), IL-12 and tumour necrosis factor-alpha upon stimulation with bacterial DNA; however, only IL-6 and IL-12 secretion became induced upon CpG ODN stimulation. We conclude that monocytes, but not B or T cells, represent the prime source of cytokines. Monocytes up-regulated expression of antigen-presenting, major histocompatibility complex class I and class II molecules in response to CpG DNA. In addition, both monocytes and B cells up-regulate costimulatory CD86 and CD40 molecules. The activation by CpG ODN depended on sequence motifs containing the core dinucleotide CG since destruction of the motif strongly reduced immunostimulatory potential.     

Decreased CD95 expression on naive T cells from HIV-infected persons undergoing highly active anti-retroviral therapy (HAART) and the influence of IL-2 low dose administration. Irhan Study Group

The functional recovery of the immune system in HIV-infected persons receiving HAART and the role of adjuvant immune therapy are still matters of intensive investigation. We analysed the effects of HAART combined with cytokines in 22 naive asymptomatic individuals, randomized to receive HAART (n = 6), HAART plus a low dose (1000 000 U/daily) of rIL-2 (n = 8), and HAART plus rIL-2 after previous administration of granulocyte colony-stimulating factor (n = 8). After 3 months of therapy, increased CD4+ T cell counts and diminished viral loads were observed in all patients, independently of cytokine addition. A decreased expression of CD95 (Apo 1/Fas) was evident in all groups when compared with values before therapy. The percentages of peripheral blood mononuclear cells (PBMC) expressing CD95 after therapy decreased by 15%, 22% and 18% in the three treatment groups, respectively (P < 0.05). Analysis of PBMC subsets demonstrated that CD95 expression was significantly reduced on CD45RA+CD62L+ naive T cells (25.3%, 22.4%, and 18.6%, respectively; P < 0.05) in each group, after therapy. Accordingly, all patients showed a reduced rate of in vitro spontaneous apoptosis (P < 0.05). Another effect induced by HAART was a significant increase in IL-2Ralpha expression on total PBMC (P < 0.05), independently of cytokine addition. Altogether, our results suggest that very low dose administration of rIL-2 (1000 000 U/daily) may be not enough to induce a significant improvement in the immune system as regards HAART alone. The employment of higher doses of recombinant cytokines and/or different administration protocols in clinical trials might however contribute to ameliorate the immune reconstitution in patients undergoing HAART.     

Regulation of interleukin-4 production in human mononuclear cells.

Interleukin (IL)-4 is a cytokine with a broad range of effects on immune cells, however, little is known regarding the regulation of its production in freshly isolated human peripheral blood mononuclear cells (PBMC). Here we report the production of IL-4 in such cells following stimulation with monoclonal antibodies (mAb) directed against different cell surface antigens. We show that triggering via CD2 is more efficient for IL-4 production than triggering via the CD3 complex. The addition of a CD28 mAb enhances IL-4 production approximately threefold. Cell depletion experiments show that among CD2 plus CD28-stimulated PBMC the production of IL-4 is restricted to the CD8-CD45RA-T cell subpopulation. mAb interfering with the binding of IL-2 to its receptor can inhibit the production of IL-4 in CD2 plus CD28-stimulated PBMC. As IL-2 induces cell proliferation and production of interferon-gamma, but not production of IL-4, it follows that IL-2 is necessary but not sufficient for IL-4 production.     

Induction of CD4 T cell proliferation and in vitro Th1-like cytokine responses to measles virus

Mechanisms that lead to induction of life-long immunity to measles virus (MV) are poorly understood. In the present study, we have assessed the activation, proliferation and cytokine secreting function of peripheral blood T cells from MV immune individuals. Expression of cell blastogenesis markers, such as increased forward light scatter and CD38 expression, peaked 5-7 days after infection of peripheral blood mononuclear cells (PBMC) with the live attenuated Edmonston strain of MV. Subset analysis revealed that both CD3- and CD3+ cells expressed activation markers but that the CD3+ T cells predominated late in the culture period corresponding to maximal proliferation and cell recovery. The majority of CD3+ T cells consisted of CD4+CD8- cells. IFN-gamma and IL-4 production similarly showed optimal production late in culture. Depletion of CD4 cells prior to culture and MV stimulation completely abrogated both IFN-gamma and IL-4 production, whereas depletion of CD8 cells did not diminish production, suggesting that CD4+CD8- T cells were principally involved in production of these cytokines. Finally, optimal IFN-gamma production was elicited at high MV doses and IL-4 at much lower doses. These results suggest that among MV immune individuals, in vitro responses to measles are dominated by CD4+ T cells that, depending on antigen dose, primarily produce a Th1-like and, to a lesser extent, a Th1/Th2-mixed pattern of cytokine release.     

Proliferation of human CD4+45R+ and CD4+45R- T helper cells is promoted by both IL-2 and IL-4 while interferon-gamma production is restricted to IL-2 activated CD4+45R- T cells

Recombinant IL-2 (rIL-2) and IL-4 (rIL-4) promote proliferation of human CD4+ T cells activated in the presence of PHA, TPA or OKT-3 monoclonal antibody (MAb), whereas the production of interferon-gamma (IFN) can be induced only by rIL-2. rIL-4 induced strong proliferative responses both in accessory cell independent assays and in the presence of autologous monocytes, but has failed to induce IFN production in any of these systems. The ability of rIL-2 to induce IFN production was strongly enhanced by the addition of monocytes, although a similar proliferative response was recorded in the absence or presence of monocytes. The MAb anti-Tac inhibited the proliferative response and the production of IFN by CD4+ T cells activated in the presence of rIL-2, whereas the proliferative response to rIL-4 was unaffected. CD4+45R+ and CD4+45R- T helper cell subsets proliferated in response to both IL-2 and IL-4. A kinetic analysis demonstrated that the production of IFN throughout a five day activation period was restricted to stimulation of CD4+45R- T cells with rIL-2. This report clearly demonstrates a dissociation of IFN production and T cell proliferation in man. While proliferation can be induced by both IL-2 and IL-4 in both the helper T cell subsets studied, IFN production was induced only in the CD4+45R- subsets and only in response to IL-2.     

HIV-1 matrix protein p17 prevents loss of CD28 expression during IL-2-induced maturation of naïve CD8(+) T cells

Na?ve CD8(+) T cells differentiate into effectors secreting various cytokines that modulate immune functions. A striking finding for most HIV-1-infected patients is that they accumulate CD8(+) T cells belonging to early and intermediate differentiated elements. Structural HIV-1 proteins, and among these the matrix protein p17, have been associated with loss of functional competence by different immune cells. We therefore evaluated the influence of p17 on na?ve CD8(+) T-cell activation and maturation. Anti-CD3 mAb preactivation and subsequent IL-2 stimulation are able to drive human naive CD(+) T cells to an effector phenotype characterized, among other features, by downregulation of the co-stimulatory molecule CD28. Strikingly, however, IL-2-induced downmodulation of CD28 was completely prevented by p17, and cells derived from p17-stimulated cultures showed a strong Tc1 polarization that was fourfold higher than that observed in IL-2-stimulated cultures.Moreover, p17 preserved a markedly high proportion of CD8(+) T cells that were able to respond to CD28 triggering with a proinflammatory cytokine storm. Our evidence suggests that p17 has important effects on cytokine polarization and phenotype of terminally differentiated CD8(+) T cells, and that new p17-based therapeutic approaches could control or prevent HIV-1-related immune disorders.     

CpG-oligodeoxynucleotides enhance T-cell receptor-triggered interferon-gamma production and up-regulation of CD69 via induction of antigen-presenting cell-derived interferon type I and interleukin-12

Bacterial cytidine-phosphate-guanosine (CpG-DNA) activates antigen-presenting cells (APC) and drives T helper 1 (Th1)-polarized immune responses in the mouse. Claims have been made that CpG-DNA costimulates murine T cells. We examined the direct and indirect effects of CpG-oligodeoxynucleotides (CpG-ODN) on human T-cell activation. CpG-ODN failed to costimulate purified human T cells activated with alpha-CD3 or alpha-T-cell receptor (TCR)alphabeta antibodies. In contrast, CpG-ODN sequence-specifically caused increased expression of CD69 on CD4 and CD8 T cells when peripheral blood mononuclear cells (PBMC) were stimulated via alpha-CD3. CpG-ODN and alpha-CD3 stimulation synergized to induce interferon-gamma (IFN-gamma) in T cells and natural killer (NK) cells, as shown by intracellular fluorescence-activated cell sorter (FACS) staining. These effects of CpG-ODN on human T cells were caused by the release of IFN type I (IFN-I) and interleukin-12 (IL-12) from PBMC. Enhancement of CD69 expression on alpha-CD3-triggered T cells could be reproduced in a coculture transwell system of purified T cells and PBMC, was inhibited by neutralizing antibodies to IFN-I and could be mimicked by adding exogenous IFN-I. Furthermore, neutralization of either IFN-I or IL-12 diminished, and in combination abolished, IFN-gamma production. These findings show that CpG-ODN potentiate TCR-triggered activation of human T cells in an APC-dependent manner.     

Activation of the immune system of cancer patients by continuous i.v. recombinant IL-2 (rIL-2) therapy is dependent on dose and schedule of rIL-2.

The effect of dose and schedule of continuous i.v. rIL-2 infusions on leucocyte subset counts, activation status of CD56+CD3- natural killer (NK) and CD3+ T lymphocytes, and cytolytic activities of peripheral blood mononuclear cells (PBMC) was studied. A single 4-day course of rIL-2 in escalating doses (0.9-11.5 x 10(6) U/m2 per day) was given to 18 patients with various types of metastatic cancer. The serum IL-2 concentration during rIL-2 therapy ranged between 23 and 64 U/ml and was proportional to the administered rIL-2 dose, as was the rebound lymphocytosis following therapy. Before therapy, the CD56+CD3- NK cells expressed low levels of the p75 chain of the IL-2 receptor (IL-2R) and virtually no IL-2R(p55). Most CD3+ T cells were IL-2R(p55-,p75-). Between 2 and 4 days following therapy, i.e. at the time of lymphocytosis, the percentage of CD56+,CD3- NK cells among the lymphocytes had increased proportional to the administered rIL-2 dose. The levels of IL-2R(p75) expression by the CD56+,CD3- NK cells had increased. The percentages of CD3+ T cells expressing IL-2R(p55), HLA-DR and CD45RO had increased proportional to the administered rIL-2 dose. The level of lymphokine- activated killer (LAK) activity against Daudi cells was also positively correlated with rIL-2 dose. Subsequently, seven patients received 4-weekly cycles of rIL-2 (2.9-4.4 x 10(6) U/m2 per day) during 4 consecutive weeks. This schedule led to marked increments in lymphocyte and eosinophil counts, and to increased cytolytic activities compared with pretreatment. We conclude that CD56+,CD3- NK and CD3+ T cells are activated differentially by continuous i.v. rIL-2 proportional to dose and duration of treatment.     

Effect of contaminating red blood cells on OKT3-mediated polyclonal activation of peripheral blood mononuclear cells

Erythrocytes are typically present as impurities in the majority of peripheral blood mononuclear cell (PBMC) preparations. This study was undertaken to investigate the effects of contaminating red blood cells (RBC) on the ability of OKT3 to activate CD4(+) and CD8(+) T cells. Surprisingly, the levels of gamma interferon, tumor necrosis factor alpha, and interleukin-1 beta (IL-1 beta) produced by PBMC upon stimulation by OKT3 were increased (P < 0.05) in a dose-dependent manner when increasing amounts of autologous RBC (RBC-to-PBMC ratios of 2:1, 10:1, and 50:1) were spiked into PBMC preparations. The OKT3-driven induction of the IL-2 receptor (CD25) and the proliferation of T lymphocytes in response to phorbol myristate acetate were not affected by the addition of RBC.