Enhancement of base hexose-monophosphate shunt activity of human polymorphonuclear leucocytes by human beta-interferon

The effect of human fibroblast interferon (HuIFN-beta) on the HMP shunt activity of human polymorphonuclear leucocytes (PMNLs) was examined. HuIFN-beta caused an increase in the base level of the HMP shunt activity. No significant increase was observed in the same PMNLs stimulated with opsonized zymosan. The augmentation of this property, generally associated with antimicrobial and cytotoxic properties of the PMNLs, may be of potential importance in host defences against microbial and malignant diseases.     

Ligand inhibition studies on the role of Fc receptors in antibody-dependent cell-mediated cytotoxicity

Subjection of human peripheral blood lymphocytes to a temp shift from 4 to 37 degrees C resulted in a shedding of Fc receptors (termed FcRI) from 40-50% of FcR-positive cells followed by their re-expression within 4 hr; a phenomenon which had no effect on the cells' antibody-dependent killing capacity. Removal of lymphocytes having an immobile form of the Fc receptor resistant to the effects of the temp shift (termed FcRII), or removal of lymphocytes bearing both FcRI and FcRII, resulted in a similar amount of reduction in ADCC activity. This was attributed, therefore, to the loss of FcRII-positive cells. The influence of isolated (shedded) FcRI and Clq on ADCC activity was investigated. Soluble FcRI was shown to inhibit ADCC mediated through the immobile Fc receptors (FcRII), despite its lack of an ability to block EA rosette formation through these receptors. Clq also had a dose-dependent inhibitory effect on ADCC. These observations are consistent with earlier findings that FcRII possesses two active binding sites; and suggest that a prerequisite for killing in ADCC is the interaction of these with the C gamma 2 and C gamma 3 domains. The ability of synthetic peptides representative of human gamma 1-chain sequences to inhibit ADCC was determined, in an attempt to locate those sites within the IgG antibody Fc region involved in interaction with two FcR binding sites. Preliminary evidence was obtained to suggest that one of these is situated within the C gamma 2 domain, in the region of residues 274 (Lys)-294 (Glu).     

The adherence of human Fc receptor bearing lymphocytes to immobilized antigen—Antibody complexes I. Specificity and use as preparative separation technique

The surfaces of polystyrene tissue culture vessels were coated with antigen—antibody complexes by trinitrophenylation of an adsorbed layer of protein followed by treatment with rabbit anti-hapten antibody. A subpopulation of human peripheral blood lymphocytes bearing Fc receptors adheres to such immobilized antigen—antibody complexes. This adhesion is antibody-dependent, requires an intact antibody Fc, and can be inhibited by preincubation of the cells with antigen—antibody complexes. Used as a preparative procedure, human lymphocytes can be fractioned with good yields into a non-adherent population depleted of cells bearing easily detectable Fc receptors and of cells mediating ADCC. This non-adherent population contains a slightly greater proportion of lymphocytes bearing surface immunoglobulin and complement receptors (i.e. B cells) than the original population and is enriched for E rosette-forming cells. After removal from the antigen—antibody complex coated surface, the adherent lymphocytes retain rabbit antibody from the substrate on their surfaces. These cells do not bear surface immunoglobulin nor complement receptors, although about half form E rosettes. After 24 hours of culture, rabbit antibody is no longer detected on the cell surfaces and the cells are able to bind new antigen—antibody complexes to their Fc receptors. Although the non-adherent fraction is always depleted of cells mediating ADCC when compared to the unnseparated population, the adherent population recovered from the substrate is variable in its ADCC activity. However, if trypsin is used to remove the adherent cells, after culture this population shows enhanced ADCC activity.     

The Use of Salmonella Schottmulleri for Mapping and Separation of Human Lymphocyte Subpopulations1

Human lymphocyte subpopulations (B cells, B₁, B₂, T₁, T₂, T₃, and T₄ cells; our denomination) have been previously identified and isolated by bacterial adherence and functional differences between them have been demonstrated. Here we examined the binding properties of Salmonella schottmulleri to human lymphocytes in peripheral blood smears and found that it binds to more lymphocyte subpopulations, namely B, T₁, T₂ and T₃ cells, than any bacteria previously tested. Thus, using only four bacteria: Salmonella schottmulleri, Brucella melitensis, Arizona hinshawii and Bacillus globigii we identified in blood smears B cells, two B and four T cell subpopulations. When we used gelatin-coupled monolayers of Sal. schottmulleri to isolate lymphocyte subpopulations, we showed that the nonadherent (T₄) cells could be efficiently separated from the adherent cells. Furthermore, we tested the isolated subpopulations for natural killing (NK) activity and for antibody-dependent cell-mediated cytotoxicity (ADCC). Using both NK and ADCC assays, we observed a significantly higher cytotoxic activity in the nonadherent cell population than in the unseparated or adherent cell populations. Also the nonadherent cells contained most of the lymphocytes that have receptors for the Fc portion of IgG and those cells described as large granular lymphocytes. We concluded that Sal. schottmulleri is a valuable new reagent for the identification and separation of human lymphocyte subpopulations.     

Sequential changes of the T lymphocytes following ER rosette formation in guinea pigs. I. Expression of Fc and complement receptors

Changes in proportions of the Fc and complement receptor (FcR, CR) positive T lymphocytes from guinea pigs following their interaction with rabbit erythrocytes (ER) were studied using EA and EAC rosette forming assays. Significant increases in the percentages of EA and EAC rosette forming cell (RFC) were observed when thymocytes or lymph node cells were assayed after ER rosette formation. Furthermore, T-enriched fraction by the ER monolayer adherence technique also showed similar or somewhat higher increases in the proportions of both EA and EAC RFC than those of unfractionated cells after contact with ER. The double rosette assay by ER with EA or EAC showed that 50-80% of the Fc and/or complement receptor positive lymphocytes bound rabbit erythrocytes simultaneously. These findings strongly suggest that at least a subset of the guinea pig T cells is altered to express Fc and/or complement receptors on their surfaces following the interaction with ER.     

Isolation of Ia-like antigen-bearing cells from human peripheral lymphocytes through the use of a monoclonal antibody to framework determinants of Ia-like antigens

A non-complement fixing monoclonal antibody (Q2/70) to framework determinants of human Ia-like antigens was used to develop a method for isolating Ia-like antigen bearing, i.e., Ia-like (+) cells and cells lacking these antigens, i.e. Ia-like (?), from human peripheral blood lymphocytes (PBL). The method was based on sensitization of PBL with the antibody Q2/70, followed by rosetting with sheep (ShE) coated with purified rabbit anti-mouse Ig antibodies, differential centrifugation on a Ficoll-Hypaque gradient, and finally recovery of Ia-like (+) and Ia-like (?) cells from the bottom and the interface of the gradient respectively. Marker analysis of the two cell subpopulations showed that the majority of the bottom cell fraction were Ia-like (+) and carried B cell markers such as membrane bound immunoglobulins (MbIg) and C3 receptors. On the other hand, the majority of the interface cell fraction were Ia-like (?) and carried T cell markers such as receptors for 2-aminoethylisothiouronium treated sheep erythrocytes (AETShE) and goat erythrocytes (GoE). Serological and functional studies showed that the Ia-like (+) cells (1) were useful targets in complement mediated cytotoxicity assays for HLA-DR typing; (2) served as stimulator but not as responder in unidirectional mixed lymphocyte reactions (MLRs); (3) did not display lytic activity in natural killer (NK) cell cytotoxicity and in antibody dependent cellular cytotoxicity (ADCC); and (4) proliferated in response to pokeweed mitogen (PWM) stimulation in the presence of helper T cells. On the other hand, the Ia-like (?) cells (1) responded to but failed to stimulate allogeneic lymphocytes in the MLRs; (2) were highly active in NK and ADCC assays; and (3) provided helper activity in PWM stimulation of purified B cells.     

Ability of rosetting or non-rosetting individual control and inflammatory macrophages to kill Escherichia coli X43 intracellularly

An autoradiographic method combined with a rosette technique was used to assess the bactericidal activity of individual control and inflammatory peritoneal macrophages (PM phi) in the presence or absence of expression of Fc receptor for IgG (FcR). There was a lack of FcR reactivity in a certain percentage of both categories of PM phi exposed to E. coli X43, a bacterium which is readily phagocytosed in the presence of specific antibody. Both rosetting and non-rosetting PM phi were capable of phagocytosing E. coli X43, but inflammatory PM phi showed a marked reduction in their capacity to ingest these bacteria compared with control PM phi. Once ingested the E. coli X43 were killed equally well by non-rosetting and rosetting control and inflammatory PM phi.     

Differences in the expression and release of DR, BR, and DQ molecules in human cells treated with recombinant interferon gamma: comparison to other interferons

This study presents a comparative analysis of the effects of different interferons (IFN) on the three recognizable subsets of human HLA class II molecules: DR, BR, and DQ. Both cellular expression and shedding of class II molecules have been determined on three different cell types. The results can be summarized as follows: class II molecules are markedly increased by IFN gamma; IFN beta has a lower enhancing effect, and IFN alpha has only a slight, if any, effect. Kinetically, the action of IFN gamma is prompter and longer lasting than that of IFN beta. DQ expression is much more enhanced by IFN gamma than either DR or BR; IFN beta has the same effect on all three subsets. Parallel changes of the cellular expression and of the shedding of these molecules are observed. A melanoma and a lymphoblastoid cell line and peripheral blood mononuclear cells show qualitatively similar modifications.     

NK cell expression of Tim-3: First impressions matter

Given the heightened interest in manipulation of co-signaling cascades for cancer immunotherapy, we sought to determine how/whether tumors decorated with therapeutic monoclonal antibodies (mAbs) impact the expression of co-signaling molecules on human NK cells. Stimulation of NK cells with aggregated IgG1 resulted in the upregulation of HAVCR2 – the gene encoding T-cell immunoglobulin and mucin-containing domain (Tim)-3 – known to be involved in the induction of peripheral T cell tolerance. This upregulation of HAVCR2 was recapitulated at the protein level, following NK cell stimulation by either mAb opsonized tumors, recombinant human IgG1 Fc multimer, and/or non-Fc stimuli e.g. IL-12/IL-18. The patterns of Tim-3 expression were temporally distinct from the FcR mediated induction of the co-signaling molecule, 4-1BB (CD137), with Tim-3 increases observed twenty minutes following exposure to Fc multimers and remaining at high levels for at least six hours, while increases in CD137 expression were first observed at the four-hour time point. Importantly, these Tim-3+ NK cells were functionally diverse, as evidenced by the fact that their ability to produce IFN-γ in response to an NK cell responsive tumor was strictly dependent upon the stimuli employed for Tim-3 induction. These data suggest that Tim-3 upregulation is the common end-result of NK cell activation by a variety of unique and overlapping stimuli and is not an independent marker of NK cell exhaustion. Furthermore, our observations potentially explain the diverse functionality attributed to Tim-3+ NK cells and should be considered prior to use of anti-Tim-3 inhibitory mAbs for cancer immunotherapy.     

In vivo anti- and pro-tumour activities of the TLR2 ligand FSL-1

TLR ligands as Th1 inducers have been investigated as potential anti-tumour agents. However, few attempts have been made to investigate the anti-tumour activity of TLR ligands as Th2 inducers. This study, therefore, was carried out to determine whether the TLR2 ligand FSL-1 as a Th2 inducers affects the growth of a QRsP tumour, a fibrosarcoma derived from the C57BL/6 (TLR2^+/+) mouse in vivo. Tumour volumes in TLR2^+/+ mice immunized with both FSL-1 and tumour-associated antigens were significantly smaller than those in control mice. Immunization with both FSL-1 and tumour-associated antigens increased the survival rate of TLR2^+/+ mice. However, surprisingly, immunization with FSL-1 alone significantly enhanced the growth of tumour. Both anti- and pro-tumour activities of FSL-1 were not observed in TLR2^−/− mice. Immunization of both FSL-1 and tumour-associated antigens induced tumour-associated antigen-specific cytolytic T cells, antibody-dependent cell-mediated cytotoxicity of natural killer cells by production of the tumour-specific antibodies, tumour lysis by complement activation and reduction of the number of regulatory T cells in the draining lymph node. Immunization with FSL-1 alone increased the number of regulatory T cells in the draining lymph node, and in vivo administration of anti-CD25 antibody into mice abrogated the pro-tumour activity of FSL-1, suggesting that regulatory T cells are involved in the pro-tumour activity.This study demonstrated that FSL-1 exhibited TLR2-mediated anti- and pro-tumour activities when immunized with and without tumour-associated antigens, respectively.     

Functional and phenotypic characteristics of bovine natural cytotoxic cells

Bovine natural cytotoxic (NC) cell activity of peripheral blood leukocytes (PBL) was studied in a chromium release assay, using xenogeneic tumor cells (YAC-1, P815) and herpes virus-infected bovine fibroblasts. The activity pattern resembled that of murine natural killer cells, in that YAC-1 cells were readily lysed, whereas P815 cells were resistant. However, 10-16 h of incubation were usually required to give appreciable cell lysis. Low, but consistent NC-activity was expressed against virus-infected fibroblasts. Using various biophysical and biochemical cell-separation methods, it was found that the effector cell active against both the xenogeneic tumor cells and virus-infected fibroblast belonged to the mononuclear phagocyte system. The indications are that at least two subpopulations of the blood monocytes, differing perhaps in maturation or clonal derivation, express NC-activity.