Expression of Fc mu receptors on human natural killer cells

A treatise on endothelial biology and exosomes: homage to Theresa Maria Listowska Whiteside

Exosomes are the current primary research focus of Dr. Theresa L. Whiteside. They are key mediators of intercellular communication in the head and neck, as well as other sites. Their effects in the tumor microenvironment are manifold and include suppression of immunity, promotion of angiogenesis, enabling of metastasis, as well as reprogramming of fibroblasts and mesenchymal stromal cells. The aim of this communication is to summarize Dr. Whiteside's contribution to the field of exosome research and details the interactions of exosomes with endothelial cells leading to recent findings on how to target endothelial cells using exosomes as a therapeutic approach.

Obstacles to ideal anti-HIV antibody-dependent cellular cytotoxicity responses

A safe and effective vaccine against HIV is a global health priority. Large-scale phase III clinical vaccine trials based on neutralizing antibodies and cytotoxic T-lymphocytes have failed to provide protection, highlighting the lack of understanding of basic immune correlates of protection against HIV. The partial success of the RV144 vaccine trial, however, sparked an intense research effort to identify and describe the protective potential of non-neutralizing antibodies. Correlates of protection analyses have identified antibodies that induced antibody-dependent cellular cytotoxicity (ADCC) as potentially important. Despite the attractiveness of utilizing ADCC antibodies for HIV vaccine design, it is important to note that effective ADCC responses are contingent on many factors. As discussed in this review, these factors are important considerations for determining the feasibility of designing an optimal ADCC antibody-inducing vaccine construct. Important determinants of ADCC responses include characteristics of the antibody, such as isotype and subclass, antigen-specificity, titer, durability and glycosylation of the constant region. Second, ADCC immune responses are highly contingent on the natural killer (NK) cell effectors. This review will describe the current state of knowledge regarding the ontogeny of NK cells, highlighting the continuous "education" they undergo that determines their functional potential upon stimulation. Other important NK cell factors, such as constant region receptor polymorphisms, cellular exhaustion, and the effects of the cytokine milieu on cellular function, will also be covered. Finally, an exciting, but yet untested, role for NK cell-mediated ADCC lies in its potential ability to eliminate latently infected cells, which harbor the viral reservoir. The review will address the potential of a two-pronged attack, where latently infected cells are induced to express HIV antigens and then eliminated by NK cells via an ADCC mechanism, with the goal of inducing a cure.

Reactive hemophagocytic syndrome in adult-onset Still disease: clinical features and long-term outcome: a case-control study of 8 patients

Reactive hemophagocytic syndrome (RHS) is a rare, life-threatening, and little-known complication of rheumatic diseases. This disorder is characterized by fever, pancytopenia, liver failure, coagulopathy, and neurologic symptoms. RHS may develop in patents who have lymphoma, organ transplantation, serious infection, and rheumatic diseases, most notably systemic lupus erythematosus and adult-onset Still disease (AOSD). Observations of specific cases of RHS in AOSD remain rare, and the significance of this syndrome during the course of AOSD remains unknown. We retrospectively studied 16 episodes of AOSD-associated RHS in 8 patients. To determine whether RHS is associated with a particular phenotype of AOSD, we conducted a case-control study from the cohort of AOSD patients seen during the same period. The estimated frequency of RHS in AOSD patients from our cohort was 15.3% (8/52). The median age at RHS diagnosis was 44.5 years. We collected clinical and laboratory data. RHS was the first manifestation of AOSD in 7 cases. The main symptoms were fever (n = 8), salmon rash (n = 6), arthralgia (n = 7), lymphadenopathy (n = 6), and shock (n = 4). Serum ferritin concentration was consistently elevated (>1000 microg/L in 8 cases), and the level of glycosylated ferritin was low in all cases (<5% in 7 cases, 15% in 1 case). Six patients presented with coagulopathy; hypertriglyceridemia was found in 6 cases. Admission to the intensive care unit was required in 4 cases. Treatment included corticosteroids (n = 8) and intravenous immunoglobulin (n = 6), cyclophosphamide in 2 cases, infliximab in the same 2 cases, and cyclosporine in 1 case. With a follow-up ranging from 2 to 15 years, the patients were in remission with prednisone plus methotrexate (n = 4), prednisone plus infliximab (n = 2), and low-dose prednisone alone (n = 2). We compared the 8 patients included in this study with 44 control patients with AOSD without RHS. Low haptoglobin levels, very high ferritin levels (>10,000 microg/L), and a normal or low neutrophil count seem to be predictive factors of the occurrence of RHS in AOSD.

Human monoclonal antibodies produced in transgenic BABκ,λ mice recognising idiotypic immunoglobulins of human lymphoma cells

Clonal idiotypic immunoglobulins of follicular lymphomas can be isolated by somatic fusion procedures. Idiotypic IgMs (Id-IgM) were isolated from two patients and used to immunise a strain of mice, deficient in mouse antibody production and engineered with yeast artificial chromosomes (YAC) containing fragments of the human immunoglobulin (Ig) micro/delta heavy chain and kappa/lambda light chain loci. Sequence analysis showed that hybridomas prepared from spleen cells of immunised mice expressed exclusively one of the six VH genes (VH1-2) present in the YAC transgene with different D/J rearrangements, and secrete fully human monoclonal antibodies (mAb) that recognised the tumour-specific IgM proteins. Further studies of the reactivity of the monoclonal anti-human Id-IgM antibodies revealed that they are specific for the individual protein of each patient and probably react with idiotypic determinants. In one case studied, the antibody recognised specifically the lymphoma cell expressing the corresponding idiotypic IgM and lysed those cells in the presence of complement. This is the first example of a human monoclonal antibody with such characteristics and may be of further use in the therapy of patients with B cell malignancies.

Channel catfish NK-like cells are armed with IgM via a putative FcmicroR

Two-color flow cytometry demonstrated that 4-8% of channel catfish PBL are positive for both F and G IgL chain isotypes, suggesting that they passively acquire serum IgM via a putative FcmicroR. These cells show spontaneous killing toward allogeneic targets, and in vitro stimulation of PBL with allogeneic cells results in an increase of double IgL chain positive cells with a concomitant increase in nonspecific cytotoxicity. Long-term cultures of alloantigen-stimulated PBL contain both sIgM(+) and sIgM(-) cytotoxic cells that transcribe message for the catfish homolog of the FcepsilonR gamma chain, but not for Igmicro and TCR-alpha,-beta, or -gamma chains. Immunoprecipitation of lysates from sIgM(+) NK-like cells with anti-IgM co-immunoprecipitated a putative FcmicroR of approximately 64 kDa. Finally, removal of IgM from sIgM(+) NK-like cells and replacement with anti-hapten antibody enabled antibody-armed effectors to kill haptenated targets that were refractory to killing by effectors armed with normal IgM. This is the first report suggesting that teleost NK-like cells express a putative FcmicroR which participates in antibody-dependent cell-mediated cytotoxicity.

Ig-binding receptors on human NK cells as effector and regulatory surface molecules

The receptors on human natural killer 9NK cells which can specifically bind the Fc portion of immunoglobulin molecules (Fc receptors) have been extensively studied. The best known and studied Fc receptor on human NK cells is FcgammaRIIIa. Interactions of NK cells with IgG antibodies via this receptor are well known to induce a signal transduction cascade and lead to antibody-dependent cell-mediated cytotoxicity (ADCC) as well as release of various cytokines. In addition, interactions with monomeric IgG and FcgammaRIIIa have been demonstrated, which result in negative regulation of NK activity and other immunomodulatory effects. Over the past several years, it has also become increasingly appreciated that human NK cells express a variety of other Fc receptors, including FcmuR, which also can mediate effector and immunoregulatory functions. Also, a novel form of FcgammaR has been demonstrated on human NK cells, termed FcgammaRIIc. Recent molecular studies have shown considerable polymorphism in the genes for FcgammaIIc and the functional consequences are being dissected. This appears to include cross-talk between FcgammaRIIIa and at least some forms of FcgammaRIIc, which may have important functional consequences.

Isolation of human NK cells and generation of LAK activity

This unit describes the preparation of natural killer (NK) cells from normal human peripheral blood and their incubation in vitro in the presence of interleukin 2 (IL-2) to yield lymphokine-activated killer (LAK) cells. A protocol is presented for isolating highly purified NK cell populations from PBMC, and another method presents steps for generating LAK cells from these purified NK cells via IL-2 stimulation. An alternate protocol describes the generation of LAK cells directly from whole, unseparated PBMC preparations instead of purified NK populations. The caveat with the alternate protocol is that LAK activity generated in this manner represents the total cytotoxic potential of all LAK precursor cells--i.e., all those PBMC that are capable of responding to IL-2 by up-regulation of cytotoxicity against NK-resistant targets. In PBMC, LAK precursor cells are found among subpopulations of both NK cells and T lymphocytes.

Expression of Functional CD32 Molecules on Human NK Cells Is Determined by an Allelic Polymorphism of the FcγRIIC Gene

Human natural killer (NK) cells were thought to express only FcγRIIIA (CD16), but recent reports have indicated that NK cells also express a second type of FcγR, ie, FcγRII (CD32). We have isolated, cloned, and sequenced full-length cDNAs of FcγRII from NK cells derived from several normal individuals that may represent four different products of the FcγRIIC gene. One transcript (IIc1) is identical with the already described FcγRIIc form. The other three (IIc2-IIc4) appear to represent unique, alternatively spliced products of the same gene, and include a possible soluble form. Analyses of the full-length clones have revealed an allelic polymorphism in the first extracellular exon, resulting in either a functional open reading frame isoform or a null allele. Stable transfection experiments enabled us to determine a unique binding pattern of anti-CD32 monoclonal antibodies to FcγRIIc. Further analyses of NK-cell preparations revealed heterogeneity in CD32 expression, ranging from donors lacking CD32 expression to donors expressing high levels of CD32 that were capable of triggering cytotoxicity. Differences in expression were correlated with the presence or absence of null alleles. These data show that certain individuals express high levels of functional FcγRIIc isoforms on their NK cells.

Expression of Functional CD32 Molecules on Human NK Cells Is Determined by an Allelic Polymorphism of the FcγRIIC Gene

Human natural killer (NK) cells were thought to express only FcγRIIIA (CD16), but recent reports have indicated that NK cells also express a second type of FcγR, ie, FcγRII (CD32). We have isolated, cloned, and sequenced full-length cDNAs of FcγRII from NK cells derived from several normal individuals that may represent four different products of the FcγRIIC gene. One transcript (IIc1) is identical with the already described FcγRIIc form. The other three (IIc2-IIc4) appear to represent unique, alternatively spliced products of the same gene, and include a possible soluble form. Analyses of the full-length clones have revealed an allelic polymorphism in the first extracellular exon, resulting in either a functional open reading frame isoform or a null allele. Stable transfection experiments enabled us to determine a unique binding pattern of anti-CD32 monoclonal antibodies to FcγRIIc. Further analyses of NK-cell preparations revealed heterogeneity in CD32 expression, ranging from donors lacking CD32 expression to donors expressing high levels of CD32 that were capable of triggering cytotoxicity. Differences in expression were correlated with the presence or absence of null alleles. These data show that certain individuals express high levels of functional FcγRIIc isoforms on their NK cells.

Tumor necrosis factor-induced expression of porcine glycoproteins gp65 and gp100 recognized by human xenoreactive natural antibodies

In the pig-to-primate model of xenotransplantation, graft rejection is initiated by binding of the recipient's xenoreactive natural antibodies (XNA), mainly of the IgM type, to antigens constitutively expressed on donor endothelial cells (EC). As a consequence of XNA binding and complement fixation, the EC become activated, which is considered to be a major mechanism promoting hyperacute as well as later phases of graft rejection. It is not clear whether binding of XNA to activated EC also contributes to delayed rejection. We asked whether EC activation by cytokines results in the expression of other novel surface antigens recognized by XNA which might become relevant in progressive stages of graft rejection. We activated porcine aortic EC and smooth muscle cells with tumor necrosis factor (TNF), interleukin 1, or lipopolysaccharide and studied expression of new XNA-binding antigens. Expression of two glycoproteins, gp65 and gp100, was strongly induced by recombinant human TNF in EC but not in smooth muscle cells. Notably, gp100 expression was specific to TNF activation, whereas gp65 could also be induced by interleukin 1 or lipopolysaccharide. Cell surface labeling indicated that gp65 is expressed on the plasma membrane. Recognition of XNA-binding antigens on resting EC occurs via alpha-galactosyl epitopes. In contrast, gp65 and gp100 were recognized independently of this epitope. Our data show that gp65 and gp100 represent selective cytokine-induced markers on EC that may have importance in a porcine-to-primate model of xenotransplantation. Conceivable functions of gp65 and gp100 are discussed.

Lysis of small cell carcinoma of the lung (SCCL) cells by cytokine-activated monocytes and natural killer cells in the presence of bispecific immunoconjugates containing a gastrin-releasing peptide (GRP) analog or a GRP antagonist

Lung cancer remains the leading cause of cancer deaths in the United States. We have developed a new immunotherapeutic approach to the treatment of small cell carcinoma of the lung (SCCL) by targeting the gastrin-releasing peptide receptor (GRP-R) expressed on the surface of these cells. Bispecific immunoconjugates were constructed by chemical fusion of a GRP analog or a GRP antagonist with monoclonal antibodies directed to the cytotoxic trigger molecules Fc gamma RI and Fc gamma RIII on various immune effector cells. We demonstrated that these bispecific immunoconjugates bound to target SCCL cells in a dose-dependent manner. In the presence of these immunoconjugates, more than 80% of SCCL cells were lysed by cytokine-activated monocytes and natural killer (NK) cells measured by a 51Cr-release assay. These data indicate that bifunctional antibodies targeting GRP may have clinical use.

Potentiation of lysis of leukaemia cells by a bispecific antibody to CD33 and CD16 (Fc gamma RIII) expressed by human natural killer (NK) cells

Bispecific antibodies recognizing tumour-associated antigens and trigger molecules expressed on immune effector cells have been shown to redirect cytotoxicity of several types of peripheral blood cells against relevant tumour targets. Among various effector cells, natural killer (NK) cells appear to play a role in defence against leukaemia. Here we report the successful chemical conjugation of monoclonal antibodies to CD33 and CD16 to create a bispecific antibody (BsAb 251 x 3G8). This bispecific antibody is capable of augmenting the killing of otherwise resistant leukaemia cells by peripheral blood lymphocytes (PBL), purified resting NK (R-NK) cells, and activated NK (A-NK) cells. BsAb 251 x 3G8 may play a role in the therapy of acute myeloid leukaemia (AML) through redirecting the cytotoxic activity of endogenous or adoptively transferred NK cells.

Expression of mRNA for cytokines in tumor-infiltrating mononuclear cells in ovarian adenocarcinoma and invasive breast cancer

Cytokine gene expression in tumor-infiltrating lymphocytes (TIL) in frozen-tissue sections of 2 types of human solid tumor--ovarian adenocarcinoma and invasive breast cancer--was examined by in situ hybridization with 35S-labeled cDNA probes for human cytokines. The proportion of cells containing mRNA able to hybridize to the antisense c-DNA probes for interleukin 2 (IL-2), tumor necrosis factor alpha (TNF alpha), interferon gamma (IFN gamma) or receptors for IL-2 (either p55 or p70) was also determined in human normal peripheral lymphoid tissues and inflammatory tissues. Few cells were positive for IL2 and TNF alpha mRNA in reactive human lymph nodes and tonsils. Inflammatory lesions, such as salpingitis or chronic active hepatitis, contained 10-20 times more cells positive for cytokine mRNA than reactive lymphoid tissue. In contrast, tumor-infiltrating lymphocytes (TIL) in the stroma of ovarian carcinomas or most ductal breast tumors only rarely expressed mRNA for TNF alpha, IL2 or IFN gamma. The intensity of mononuclear cell infiltration in these tumors correlated positively with the percentage of cells which expressed mRNA for IL-2, TNF alpha and IL-2R. In those ductal breast carcinomas which contained intracellular or intraductal mucins, up to 30% of lymphoid cells in the tumor stroma were positive for IL-2, TNF alpha, IFN gamma and IL-2R. Thus, strong evidence for local activation of mononuclear cells in situ, exemplified by the expression of genes for cytokines, was obtained only in inflammatory lesions and in mucin-producing breast carcinomas. In most carcinomas studied, few TIL expressed genes for cytokines as measured by in situ hybridization. Thus, human solid tumors appear to differ in their ability to induce gene expression for cytokines in TIL.