Normal Allogeneic Cells Research Articles

Down-regulation of HLA-A and HLA-Bw6, but not HLA-Bw4, allospecificities in leukemic cells: an escape mechanism from CTL and NK attack?

AbstractHuman leukocyte antigen (HLA) class I antigen defects may have a negative impact on the growing application of T-cell–based immunotherapeutic strategies for treatment of leukemia. Therefore in the present study, taking advantage of a large panel of HLA class I allele–specific human monoclonal antibodies, we have compared HLA class I antigen expression on leukemic cells with that on autologous and allogeneic normal cells. Down-regulation of HLA-A and/or -B allospecificities was present in the majority of the patients studied. However, down-regulation did not affect all HLA class I alleles uniformly, but was almost exclusively restricted to HLA-A allospecificities and to HLA-B allospecificities which belong to the HLA-Bw6 group. The latter allospecificities, at variance from those that belong to the HLA-Bw4 group, do not modulate the interactions of leukemic cells with natural killer (NK) cells. Therefore, our results suggest that the selective down-regulation of HLA-A and HLA-Bw6 allospecificities associated with HLA-Bw4 preservation provides leukemic cells with an escape mechanism not only from cytotoxic T lymphocytes (CTLs), but also from NK cells. As a result T-cell–based immunotherapeutic strategies for leukemia should utilize HLA-Bw4 alloantigens as restricting elements since a selective HLA-Bw4 allele loss would provide leukemic cells with an escape mechanism from CTLs, but would increase their susceptibility to NK cell–mediated lysis. (Blood. 2004;103:3122-3130)

Development of self-recognition systems in natural killer cells.

Differentiation of NK cells is bone marrow dependent. Although all the factors necessary for NK differentiation are yet to be fully characterized, IL-15 has emerged as the most likely candidate that drives terminal differentiation of NK cells. Other cytokines are needed for the expansion and maintenance of the progenitor population. Although the in vivo role for IL-15 cannot be established without the generation of either IL-15 or IL-15R alpha deficient mice, in vitro data suggests that it is responsible for the generation of lytic, NK1.1+ cells from immature progenitors. So far, it has not been possible to obtain Ly-49+ cells from marrow or fetal-derived progenitor cells in vitro. Stromal cells along with cytokines may be necessary to induce expression of Ly-49 on NK1.1+ cells. Expression of the NK receptors seems to be a sequential process with expression of IL-2/15R beta on progenitor cells occurring first followed by the expression of NK1.1 and then probably Ly-49. The same sequence seems to hold true in vivo as well, Ly-49 surface expression on splenic NK1.1+ cells is first detected 4-6 days after birth, and the frequency of cells expressing Ly-49 receptors reaches adult levels by days 20-24. Despite the lack of expression of Ly-49 receptors by fetal NK1.1+ as well as bone marrow derived NK1.1+ cells, they are able to distinguish between MHC class Ihi and class Ilo targets. This suggests that these NK1.1+Ly-49- cells express non-Ly-49 class I receptors. Efforts in the future need to be focused on elements responsible for the expression of Ly49 on these NK1.1+ cells in order to establish an in vitro system in which establishment of the Ly-49 repertoire can be studied.

Adeno-associated virus vectors for gene therapy of the hematopoietic system.

Over the past 30 years, bone marrow transplantation has come to be accepted as standard curative therapy for many pathophysiologic conditions (Forman et al. 1994) including malignancies (Brenner et al. 1993) and metabolic diseases (Blaese 1993). Thus, the reconstitution of the hematopoietic system with normal allogeneic cells capable of providing long term engraftment with disease-free, physiologically functional cells has been used to treat various inherited diseases including severe combined immunodeficiency disease (SCID), lysosomal storage disorders and various hemoglobinopathies. However, difficulties in acquisition of histocompatible marrow cells for transplantation and onset of graft vs host disease has led to the continued search for better therapeutic strategies. Meanwhile, the delineation of the genetic bases of many inherited diseases and the subsequent isolation of appropriate wild-type genes promoted the feasibility of disease correction at the DNA level. To this end, much effort has focussed upon the development of both the identification of genetic strategies as well as efficient methods of delivery of therapeutic genes to appropriate target cells.KeywordsHematopoietic Progenitor CellRous Sarcoma VirusSevere Combine Immunodeficiency DiseaseNondividing CellAdenosine Deaminase DeficiencyThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Specific functions of human NK cells

Since natural killer (NK) cells lack both CD3/TCR molecules and surface Ig, it is generally thought that they are unable to recognize antigens. However, CD3-CD16+ cells were found to respond in MLC against irradiated allogeneic mononuclear cells and to lyse normal PHA blasts derived from the stimulating donor, but not autologous cells or cells derived from most allogeneic donors. A similar pattern was obtained with cloned NK cells, thus indicating that the ability to specifically recognize given normal allogeneic cells is a clonally distributed function. Moreover, analysis of NK clones for their ability to lyse either tumor cells or normal PHA blasts (both derived from individual cancer patients) indicated that the two phenomena are distinct. Analysis of a large number of NK clones derived from a given individual for their ability to lyse a panel of allogeneic donors allowed the identification of at least four groups of clones characterized by unique patterns of reactivity ("specificities"). We further studied the mode of inheritance of the various NK-defined specificities: all the characters "susceptibility to lysis" by NK clones (displaying one or another specificity) segregated independently, were inherited in an autosomic recessive manner and were carried by chromosome 6. The finding of clonally distributed specific functions in NK cells suggested the existence of clonally distributed receptor molecules. Along this line mAbs were raised against NK clones, and screened for their ability to trigger the immunizing clones: two mAbs (termed GL183 and EB6) were directed against a novel family of 58-kDa surface molecules.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo induction of γ/δ T cells with highly potent and selective anti‐tumor cytotoxicity

High frequencies of CD5+TcR alpha/beta- T cells were induced in the peritoneal cavity of rats immunized with syngeneic W439 lymphoma cells. These TcR alpha/beta- cells expressed TcR delta mRNA as analyzed by the polymerase chain reaction technique. The delta + (TcR gamma/delta +) T cells were of the CD2+, CD3+, CD4-, CD8+, CD45RB+ phenotype and showed stronger anti-tumor cytotoxicity compared to the TcR alpha/beta + T cells. The cytotoxic effects of both alpha/beta and gamma/delta T cells were selective for the W439 lymphoma cells and were not directed to other syngeneic tumors, natural killer targets and syngeneic or allogeneic normal cells. T cells, including both alpha/beta and gamma/delta cells, were induced when WF rats were immunized with allogeneic BN spleen cells. In this case the gamma/delta T cells showed allo-selective cytotoxicity, although weaker compared to the TcR alpha/beta + T cells. The gamma/delta T cells, induced by immunization with either W439 cells or BN spleen cells, were selective for the immunogen used and had no effect on irrelevant target cells, indicating that these effector cells were not activated by a shared gamma/delta T cell-related superantigen. Since highly potent tumor-selective gamma/delta cytotoxic T lymphocytes could be induced by syngeneic lymphoma cells, we suggest a role for gamma/delta T cells in the defense against certain types of tumors.

Susceptibility or resistance to lysis by alloreactive natural killer cells is governed by a gene in the human major histocompatibility complex between BF and HLA-B.

The specificity recognized on normal allogeneic cells by a given alloreactive (1-anti-A) natural killer clone is controlled by a gene locus termed EC1. Because the EC1 locus was previously shown to be located on chromosome 6, families characterized by a recombinant major histocompatibility complex haplotype were analyzed to map this locus more precisely. The breakpoint of recombination was studied by standard HLA typing, complement typing, and restriction fragment length polymorphism analysis of a series of genes located between the complement cluster genes and HLA-B within the major histocompatibility complex region. Three of 10 families analyzed were informative. From the data obtained, the EC1 locus maps between BF and HLA-B and presumably is one of the normal genes recently described in this region.

Identification of four subsets of human CD3-CD16+ natural killer (NK) cells by the expression of clonally distributed functional surface molecules: correlation between subset assignment of NK clones and ability to mediate specific alloantigen recognition.

In previous studies we identified a surface molecule (termed GL183) capable of mediating cell activation and selectively expressed by a subset of human CD3-CD16+ natural killer (NK) cells. In this study we analyzed whether other subset-specific functional molecules were expressed in GL183- NK cells. To this end, mice were immunized with the PE29 (CD3-CD16+GL183-) NK clone. Monoclonal antibodies (mAbs) were selected by screening the hybridoma supernatants for their ability to trigger the cytolytic activity of clone PE29 against the human myelomonocytic leukemia U937. The EB6 mAb (IgG1) triggered the PE29 clone, but not a GL183+ clone used as a control. EB6+ cells ranged between 1 and 13% of peripheral blood lymphocytes and were largely included in the CD3-CD16+CD56+ cell populations (only less than 2% of EB6+ cells were CD3+). Analysis of resting or activated CD3-CD16+ populations, or clones for the expression of EB6 or GL183 mAbs, allowed us to identify four distinct, phenotypically stable, NK subsets (EB6+GL183-; EB6+GL183+; EB6-GL183+; EB6-GL183-). Similar to GL183 mAb, the EB6 mAb selectively triggered the NK subset expressing the corresponding surface antigen to lyse human tumor cell lines including U937, IGROV-I, M14, and A549. In addition, EB6 mAb sharply inhibited the cytolytic activity of EB6+ clones against P815, M12, and P3U1 murine target cells. In EB6+GL183+ ("double-positive") clones both EB6 and GL183 mAb inhibited the redirected killing of P815 cells induced by anti-CD16, anti-CD2 mAbs and phytohemagglutinin (PHA). Similar to GL183 molecules, molecules precipitated by EB6 mAb were represented by either single 58-kD chain or double chains of 55 and 58 kD (with no detectable differences in EB6+GL183- or EB6+GL183+ clones). In sequential immunoprecipitation experiments using the double-positive clones CEG52 and CA25.50, preclearing of cell lysates with EB6 or GL183 mAb removed only EB6 or GL183 molecules, respectively, thus indicating that the two antigenic determinants are carried by two distinct molecules. Peptide map analysis indicated that EB6 (or GL183) molecules precipitated from double-positive clones were identical to the corresponding molecules isolated from single-positive ones. On the other hand, comparison of the EB6 and GL183 maps revealed peptides that were unique to each molecule, although most of the major peptides migrated to identical positions. We further investigated whether correlation existed between the phenotypic assignment of NK clones and their ability to mediate specific lysis of normal allogeneic cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Early Development of CD8‐Negative and CD8‐Positive MHC‐Unrestricted Cytotoxic Cells Induced by Alloantigen Inoculation in Mice

Peritoneal cells (PC) in C57B1/6 (B6, H-2b) mice receiving an intraperitoneal (i.p.) injection of allogeneic BALB/c (H-2d) spleen cells demonstrated potent cytotoxic activity against syngeneic, xenogeneic, third-party allogeneic tumors as well as H-2d derived tumors. Maximum cytotoxic activity against various tumors other than H-2d derived tumor, B16 (H-2b) was elicited on day 3 post allosensitization and decreased drastically thereafter, whereas cytotoxic activity against P815 (H-2d) peaked 3 days after the inoculation and maintained the peak activity thereafter. Surface phenotype of PC responsible for the cytotoxic activity against B16 was Thy-1+/-, Lyt-2-, L3T4-, asialo GM1 (AGM1)+, and that of PC against P815 was Thy-1+, Lyt-2+ (or Lyt-2+/-), L3T4-, AGM1+. These phenotypes showed similar phenotypes to the counterparts against B16 and against P815 in spleen cells induced by intravenous inoculation of alloantigen. When mice were pretreated i.p. with anti-AGM1 antibody before the allosensitization, anti-P815 cytotoxic-activity in PC was completely diminished. Similar activity in spleen, however, was enhanced by i.v. treatment with the antibody before the i.v. inoculation of alloantigen. The data clearly demonstrate that in vivo inoculation of B6 mice with normal allogeneic cells induces "NK-like" CD8- cytotoxic cells and "anomalous" CD8+ cytotoxic cells in PC.

Specific recognition of human CD3-CD16+ natural killer cells requires the expression of an autosomic recessive gene on target cells.

We analyzed the recently defined ability of CD3-CD16+ cells to specifically recognize and lyse normal allogeneic target cells (PHA-induced blasts). The susceptibility to lysis by a given alloreactive natural killer (NK) clone ("1 anti-A") was expressed by PHA blasts derived from 9 of 38 random donors analyzed. In all instances, the specific lysis of "susceptible" target cells was greater than 35% while that of "nonsusceptible" targets was less than 6% at an E/T cell ratio of 5:1. In addition to 1 anti-A, A anti-1 specific CD3-CD16+ clones could also be isolated from the reverse MLC combination. The relationship existing between lysis of normal allogeneic cells or tumor cells by the same CD3-CD16+ effector cell has been investigated: 1 anti-A specific CD3-CD16+ clones lysed PHA blasts of three of six cancer patients, while they lysed fresh tumor cells (ovarian carcinoma) from all six patients. The type of inheritance of the character "susceptibility to lysis" was analyzed in representative families. This analysis revealed that the character is inherited in an autosomic recessive fashion, and it is therefore different from MHC. We further investigated the type of segregation of the opposite character "resistance to lysis" (which is inherited in a dominant mode). The finding that this character segregated in all donors expressing given MHC haplotypes indicated that the gene regulating the expression of the NK-defined alloantigen is present on chromosome 6.

Human Monoclonal Antibodies Reactive with Cell Surface Antigens on Human Leukemia Cell Lines: Many Antibodies Are (Auto)antibodies

Primary Epstein Barr Virus (EBV) transformants from peripheral blood mononuclear cells (PBM) established in macrocultures were screened for the secretion of antibodies reactive with cell surface antigens on one or another of two indicator human leukemic cell lines and fused with the HMMA2.11TG/O human fusion partner. Human monoclonal antibodies (HuMAbs) were readily obtained. Relative oligoclonality of the primary EBV macrocultures was documented by the number of antibody secreting hybridomas (1-100%). The method permitted preselection for fusion of transformants producing antibodies of certain specificities and/or class. Fourteen HuMAbs, primarily of the IgM class, have been obtained. Those IgM HuMAbs obtained from patients with active diseases, e.g. Acute Lymphoblastic Leukemia (3 HuMAbs), and HIV infection (4 HuMAbs), were found to have a relatively broad spectrum of reactivity with cell lines of various hematopoietic lineages and normal cells, although several show selective reactivity with T cell lineage tumors or a selected population of cells. HuMAbs from normal donors of both the IgG and IgM class were obtained. The IgM HuMAbs from one volunteer reacted primarily with autologous and allogeneic macrophages (autologous PBM from the other patients were not available) as well as a diverse number of hematopoietic cell lines. From others, the IgG HuMAbs demonstrated a more restricted spectrum of reactivity, while the IgM HuMAbs reacted with both autologous and allogeneic normal cells. Thus, the B cell repertoire contains cells capable of secreting cell surface reactive antibodies and many of these antibodies express characteristics of autoantibodies. Those that did not react with autologous or allogeneic PBM may react with other autoantigens which have been expressed on the malignant cells used as screening targets or may represent true antitumor antibodies.

Molecular interactions required for triggering alloantigen-specific cytolytic T lymphocytes.

Affinity-purified class I proteins in detergent solution can be directly immobilized on plastic by a simple dilution procedure. The immobilized Ag retains its native structure and will trigger specific, TCR-mediated degranulation of cloned CTL. Stimulation of the response is dependent on the surface density of Ag, and displays a critical threshold density below which response does not occur. Individual clones differ with respect to the threshold density required for activation, but these differences are not large. With one exception, the cloned lines examined respond to Ag densities comparable to that found on normal allogeneic cells, and critical threshold densities varied over about a fourfold range. Coimmobilization of alloantigen and nonantigenic class I protein of a different specificity has the effect of decreasing the threshold density of alloantigen required for response to occur. This augmentation is specific for class I, coimmobilized class II protein does not affect responses, and is very likely mediated by Lyt-2 (CD8) interaction with nonpolymorphic determinants on the class I protein. Thus, class I alloantigen is the necessary and sufficient ligand for activation of most allogeneic CTL clones, and both TCR and Lyt-2 interactions contribute to the response. The results described here for effector CTL are compared with those previously found in examining the ligand requirements for activation of precursor CTL.

Surface molecules involved in CD3-negative NK cell function. A novel molecule which regulates the activation of a subset of human NK cells

Natural killer cells are characterized by the lack of CD3/TCR molecules and by the expression of CD16 and CD56 (NKHI or Leu19) surface antigens. In addition to their ability to lyse certain tumor target cells, they release lymphokines including tumor necrosis factor and interferon gamma. Another unexpected functional capability of at least some NK cells is the ability to specifically recognize and lyse certain normal allogeneic cells (PHA-induced blasts). MAbs directed to CD2 or to CD16 surface molecules induced triggering of NK cells leading to target cell (p815) lysis in a redirected killing assay. Importantly, different from induction of T cell activation, single anti-CD2 MAbs were sufficient to trigger NK cell function. Another MAb (GL183) inducing NK cell triggering recognized a novel surface molecules expressed on 20-50% of resting or cultured NK cells. Cloned GL183+ cells displayed a variable degree of cytolytic activity against a number of human target cells of different histotype; moreover, this activity was strongly enhanced by the addition of GL183 MAb. On the other hand, GL183 MAb inhibited lysis of murine lines (including P815). Thus on P815 target cells GL183 MAb has an effect antithetical to that of other stimuli including PHA, anti-CD2 or anti-CD16 MAbs. GL183 MAb, added simultaneously to one or another of the stimuli above, strongly inhibited the target cell lysis induced by these stimuli. Thus, GL183 may represent an important molecule in the process of activation/regulation of phenotypically-defined NK cell subsets.

LY-2+ effectors cytotoxic for syngeneic tumor cells: generation by allogeneic stimulation and by supernatants from mixed leukocyte cultures.

The present study was aimed at gaining insight into means by which stimulation of mouse spleen cells with allogeneic normal cells in mixed leukocyte cultures (MLC) can result in the generation of effector cells cytotoxic for syngeneic tumor or transformed cells. Stimulation of lymphocytes from BALB/c or C3H mice for 5 days with cells from mice of every allogeneic strain tested, in medium containing mouse serum and lacking xenogeneic serum, resulted in the activation of effectors cytotoxic for syngeneic cells transformed spontaneously or by SV40, polyoma or adenovirus. In each experiment, all of the syngeneic transformed cell lines, as well as clones derived from these lines, were lysed to the highest degree by effectors obtained from the same culture, and therefore stimulated with cells from the same allogeneic strain. Although the particular allogeneic sensitizing strain that induced the highest cytolytic activity varied between experiments, effectors obtained from the culture with the highest cell recovery always exhibited the greatest cytotoxicity against all the syngeneic transformed cells and clones. Lysis was mediated predominantly by Ly-2+ effectors; total lytic units of cytotoxicity recovered after treatment with monoclonal anti-Ly-2 antibody and complement (C) were reduced by 85 to 90% compared to cells treated with C alone. Lysis of syngeneic tumor cells by the allosensitized effectors in cytotoxicity assays was not inhibited by the addition of unlabeled "blocking" lymphocytes from the allogeneic strain used for sensitization. In addition, it was found that lymphocytes cultured without stimulating cells for 5 days in medium supplemented with supernatants from secondary MLC that are known to contain high levels of lymphokines, mediated high levels of cytotoxicity on all the transformed cells tested, but lacked detectable cytotoxic activity for syngeneic or allogeneic Con A blasts. The MLC supernatant-activated effectors that lyse the transformed cells are phenotypically CTL, because treatment with anti-Ly-2 and C reduced lytic activity by approximately 75%. Taken together, these findings suggest that the generation in MLC of Ly-2+ effector cells cytotoxic for syngeneic transformed cell lines might not be due, in some cases, to lymphocyte responses to particular alloantigens on the stimulating cells that are cross-reactive with "alien" histocompatibility antigens on transformed cells, but rather is due to effector cell activation by lymphokines produced during allogeneic stimulation.

Transient Immunodeficiency During Asymptomatic Epstein-Barr Virus Infection

In vivo and in vitro humoral and cellular immune responses were studied in a 2 1/2-year-old girl immediately before, during, and after an asymptomatic infection with Epstein-Barr virus. During the acute EBV infection, the patient's peripheral blood mononuclear cells were deficient in immunoglobulin synthesis and suppressed the in vitro immunoglobulin synthesis of normal allogeneic cells. In vitro mitogen transformation of lymphocytes was reduced. In vivo antibody responses to the T cell-dependent antigens bacteriophage phi X 174 and Keyhole limpet hemocyanin were markedly depressed. These studies suggest that suppressor cells induced during acute EBV infection not only suppress immunoglobulin synthesis in vitro, but also interfere with in vivo antibody synthesis.

Depletion of human NK cells with monoclonal antibodies allows the generation of cytotoxic T lymphocytes without NK-like cells in mixed cultures.

In vitro stimulation of human mononuclear cells with x-irradiated autologous lymphoblastoid cell line (LCL) or allogeneic normal cells in mixed leukocyte cultures (MLC) was previously shown to result in the generation of OKT3+ OKT8+ cytotoxic T lymphocytes (CTL) lytic for allogeneic and autologous LCLs and also of natural killer- (NK) like cells that are OKT3- and primarily OKT8- and are lytic for HLA- NK-sensitive K562 cells. The origin of the NK-like cells was not previously known because, although the majority of fresh human NK cells react with monoclonal antibodies OKM1 and B73.1, lymphocytes bearing these markers are not detected several days after the onset of MLC, when NK-like cells are present. In this study, experiments were undertaken to determine whether NK-like cells generated after stimulation with x-irradiated pooled allogeneic normal cells (poolx) or with autologous LCL are derived from cells expressing antigens reactive with monoclonal antibodies OKM1 or B73.1, which react with fresh NK cells. Mononuclear cells, depleted of monocytes, were stained with OKM1 or B73.1 and fluorescein-labeled goat anti-mouse IgG. Lymphocytes depleted of OKM1+ or B73.1+ cells, by fluorescence-activated cell sorting, and lymphocytes that were stained but not sorted were stimulated for 7 days with either poolx or autologous LCL. The generation of NK-like activity was decreased at least 90% after depletion of cells reactive with OKM1 or B73.1, whereas the generation of CTL against autologous and allogeneic LCL was minimally affected. These findings show that NK-like cells generated in MLC are derived from cells that express the phenotype of fresh NK cells (OKM1+ or B73.1+) and that CTL can be generated in cultures in which relatively little NK-like activity is concomitantly detected, by depleting NK cells with monoclonal antibodies before stimulation.

Alloreactivity and Tumor Antigens: Generation of Syngeneic Antilymphoma Killer Lymphocytes by Alloimmunization of Mice With Normal Cells<xref ref-type="fn" rid="fn2">2</xref><xref ref-type="fn" rid="fn3">3</xref>

The possibility of obtaining a syngeneic antitumor effect by immunization with normal allogeneic cells was investigated by tests of the lytic activity of peritoneal exudate cells (PEC) of BALB/c mice immunized with lymphoid cells of either a single strain or a pool of six different allogeneic strains on the syngeneic Moloney virus-induced lymphoma YC8 target and on one of its clones designated YC8-D1. Significant cytotoxicity on both targets but not on two other BALB/c lymphomas was obtained with PEC of BALB/c mice singly immunized to the non-H-2-incompatible but H-2-compatible DBA/2 or B10.D2 lymphoid cells. The lack of lysis of YC8 cells by PEC of BALB/c mice immune to B10.A (H-2k,d) suggests that the in vitro killing was restricted by Kd-IEd region products of the major histocompatibility complex. Pool immunization was effective in generating antitumor cytotoxic lymphocytes only when DBA/2 lymphoid cells were included in the pool. The pattern of reactivity of effectors elicited in (BALB/c x DBA/2)F1 and in (BALB/c x B10.D2)F1 mice by immunization with DBA/2 and B10.D2 cells showed that at least two sets of antigens are recognized on YC8 targets, one shared by DBA/2 and B10.D2 tissues and the other expressed by DBA/2 cells only. Cold target blocking experiments indicated that the same effectors recognized non-H-2 antigens of DBA/2 and the cross-reacting YC8 determinants. The antitumor effect was mediated by T-cells, since it was abrogated by treatment of effectors with anti-Thy 1.2 serum plus complement. These data indicate that determinants defined by cytotoxic T-lymphocytes are expressed on the BALB/c lymphoma YC8 and cross-react with non-H-2 antigens of DBA/2 and B10.D2 strains.

Rosette and blastogenesis inhibition by plasma from Hodgkin's disease and other malignancies: Positive correlation in stage I and II Hodgkin's disease

The simultaneous presence of both rosette- and mitogen-induced blastogenesis inhibitors was measured in the plasma from 29 patients with active Hodgkin's disease, 21 patients with advanced lung cancer, nine patients with diffuse histiocytic lymphoma, 25 patients with non-Hodgkin's lymphoma, and 17 patients with a variety of solid tumors. Only patients with active Hodgkin's disease consistently demonstrated factors which interfered with both rosetting and mitogenesis when normal allogeneic cells were utilized. While a similar proportion of patients with early and late Hodgkin's disease possessed plasma which could inhibit both tests, a significant correlation between these tests was observed only in Stage I and II disease. Varying degrees of inhibition of these tests was also observed when plasmas from patients with other malignancies were tested. Both lung cancer and histiocytic lymphoma plasma contained a factor which was capable of significantly inhibiting in the rosette assay when compared to normal human serum. Plasma from these patients also demonstrated inhibition of blastogenesis, but unlike Hodgkin's disease, no correlation between these activities could be demonstrated. Neither patients with diffuse or nodular lymphocytic lymphoma nor patients with solid tumors had significant plasma inhibition in either assay.

Normal Suppressor-Cell Activity in Systemic Lupus Erythematosus. ASstudy on 26 Cases

Suppressor-cell activity of 26 SLE patients suffering from active disease was compared to that of 15 healthy controls. ConA-induced and spontaneous suppression was evaluated. The mitogen-driven proliferation of normal allogeneic cells was significantly impaired by ConAinduced as well as spontaneous suppressor cells. However, no difference in suppressor-cell activity could be demonstrated between SLE patients and controls.

Sensitization of lymphocytes against pooled allogeneic cells. II. Characterization of effector cells cytotoxic for autologous lymphoblastoid cell lines.

Stimulation of human lymphocytes in mixed leukocyte culture (MLC) with x-irradiated pooled allogeneic normal cells (poolx) was previously shown to result in generation of effector cells cytotoxic for autologous Epstein-Barr virus- (EBV) transformed lymphoblastoid cell lines (LCL). This study was undertaken to determine whether lysis of the autologous EBV- transformed LCL cells by pool-stimulated cells is mediated by cytotoxic Tc lymphocytes (Tc) or natural killer- (NK) like cells, both of which are generated in MLC. In the first series of experiments, proliferating cells were eliminated by treatment of pool-stimulated cells with 5 X 10(-5) M 5-bromodeoxyuridine (BUdR) and light. The remaining cells failed to lyse allogeneic normal lymphocytes and autologous LCL cells, whereas cytotoxicity against NK-sensitive K562 leukemia cells was retained. In the second series of experiments, pool-stimulated effector cells were treated with monoclonal anti-human Tc cell antibodies, OKT3 or OKT8, and complement (C). The cells recovered after antibody and C treatment were diminished in their ability to lyse allogeneic normal lymphocytes as well as autologous LCL cells, whereas their cytotoxicity against K562 leukemia cells was unaffected. These combined results provide strong evidence that lysis of autologous LCL cells by lymphocytes stimulated with pooled allogeneic normal cells is mediated by Tc rather than NK-like cells.

Monoclonal antibodies which distinguish between human NK cells and cytotoxic T lymphocytes.

Although it is widely accepted that T cells have a major role in specific tumour immunity, there is now much evidence that natural killer (NK) cells, which exist in many species and spontaneously lyse certain tumour cells in vitro, provide early resistance against tumour growth. Human NK-cell activity can be augmented in vitro by interferon and its inducers, including polyinosinic:polycytidylic acid (poly I:C); furthermore, NK-like activity is generated in mixed leukocyte cultures (MLCs) as is specific cytotoxic T-cell (Tc) activity. When effector cells generated in human MLCs lyse allogeneic or autologous virus-transformed or tumour cells, it has been difficult to evaluate the relative contributions of Tc and NK-like cells to the lysis because the latter, like T cells, can form rosettes with sheep erythrocytes and react with xenogeneic anti-human thymocyte serum. We report here that monoclonal antibodies against human mononuclear cell subpopulations can distinguish Tc from NK and NK-like cells. OKT3 or OKT8 monoclonal antibodies (reactive with virtually all or a subset of T cells, respectively) with complement (C') ablate MLC-generated Tc activity against allogeneic normal cells but do not decrease lysis of HLA-negative, NK-sensitive K562 leukaemia cells by NK, poly I:C-activated NK or MLC-activated NK-like cells. In contrast, OKM1 monoclonal antibody (reactive with a low proportion of non-adherent mononuclear cells as well as macrophages) with C' causes marked diminution of NK and poly I:C-activated NK-cell activity.