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L Moretta

Publications and source records attributed to L Moretta.

At least 109 records · Page 6Linked to original sources
PubMed1996

The human leukocyte antigen (HLA)-C-specific "activatory" or "inhibitory" natural killer cell receptors display highly homologous extracellular domains but differ in their transmembrane and intracytoplasmic portions.

Natural killer cells express clonally distributed receptors specific for major histocompatibility complex class I molecules. The human leukocyte antigen (HLA)-C-specific receptors have been molecularly identified and cloned. They exist not only as inhibitory (p58) but also as activatory (p50) receptors. Here we show that p50 and p58 are highly homologous in their extracellular regions formed by two Ig-like domains. In contrast, major differences exist in their transmembrane and cytoplasmic portions. Whereas p 58 displays a 76-84-amino acid cytoplasmic tail containing an unusual antigen receptor activation motif, p50 is characterized by a shorter 39-amino acid tail. In addition, whereas p58 has a nonpolar transmembrane portion, p50 contains the charged amino acid Lys. These data strongly suggest that receptors with identical HLA-C allele specificity can mediate functions of opposite sign owing to their different transmembrane/cytoplasmic portions.

Amino Acid Sequence↗
PubMed1996

CD31-triggered rearrangement of the actin cytoskeleton in human natural killer cells.

In this report, we analyze whether CD31, also known as platelet-endothelial cell adhesion molecule-1 (PECAM-1), can transduce an outside-in signal in human natural killer (NK) lymphocytes in vitro. We show that CD31, but not HLA class-I cross-linking triggers an outside-in transmembrane signal in NK lymphocytes, mediating cell spreading and cytoskeletal rearrangement. These phenomena are Mg2+, but not Ca2+ dependent, suggesting that signal transduction elicited by CD31 cross-linking may involve an associated integrin. Two possible candidates would be alpha v and alpha L, whose function is known to depend on Mg2+. However, the CD31-induced cytoskeletal rearrangement was not reduced by the use of alpha v- or alpha L-specific F(ab')2, suggesting that CD31 could transduce a signal by itself or by association with a still-undefined integrin. Moreover, talin, but not vinculin or tubulin, appears to co-localize with actin microfilaments in the membrane ruffles of NK cells that undergo cytoskeleton rearrangement following CD31 cross-linking. Both spreading and cytoskeletal rearrangement appear to be regulated by intracellular cyclic-3',5'-adenosine monophosphate (cAMP). Indeed, the activator of the adenylyl cyclase, forskolin, inhibited cell spreading and cytoskeletal rearrangement induced by CD31 cross-linking. This phenomenon was also observed using the membrane-permeants cAMP analog Sp adenosine-3', 5' -cyclic monophosphothioate (Sp-cAMPS), but not its inactive isomer Rp-cAMPS. Likewise, adhesion of NK lymphocytes to NIH/3T3 murine fibroblasts transfected with the cDNA encoding human CD31 was blocked by increasing intracellular cAMPS levels. We suggest that intracellular cAMP may be involved in CD31-mediated signal transduction, and may regulate NK-endothelial cell adhesion and possibly, the tissue localization of NK cells.

3T3 Cells↗
PubMed1996

Dissection of lymphocyte function-associated antigen 1-dependent adhesion and signal transduction in human natural killer cells shown by the use of cholera or pertussis toxin.

The effect of the guanosine triphosphate-binding protein (G-protein) inhibitors cholera toxin (Ctx) and pertussis toxin (Ptx) has been analyzed on lymphocyte function-associated antigen 1 (LFA-1)-dependent adhesion and signal transduction in human natural killer (NK) cells. Ctx, but not Ptx, inhibited the LFA-1-dependent adhesion of NK cells to tumor target cells which constitutively express the intercellular cell adhesion molecule-1 (ICAM-1) and to NIH/3T3 mouse fibroblasts stably transfected with human ICAM-1. This effect was detectable only by the use of the entire Ctx but not of the Ctx B subunit. In addition, Ctx could inhibit both NK cell binding and spreading to purified ICAM-1 protein. NK cell treatment with Ctx modified neither the surface expression of LFA-1 nor its Mg2+ binding site. These findings, together with the absence of any detectable effect of Ctx on the constitutive phosphorylation of LFA-1 alpha, suggests that this toxin modifies the avidity of LFA-1 for ICAM-1 by acting on LFA-1-cytoskeletal protein association. Unlike Ctx, Ptx did not affect NK cell adhesion. The effects of Ctx and Ptx are unlikely to depend on intracellular levels of cyclic adenosine 3',5'-monophosphate (cAMP), since a strong increase of cAMP was induced by both toxins. Moreover, this was confirmed by the observation that the LFA-1-dependent adhesion was not inhibited by the adenylate cyclase activator forskolin (FSK), the phosphodiesterase inhibitor isobutyl-1-methylxanthine (IBMX), or both, which increase intracellular cAMP levels. Unlike the differential effect on cell adhesion, both the intracellular calcium [Ca2+]i increase and phosphoinositide breakdown mediated via LFA-1 were consistently inhibited in a dose-dependent manner by both Ctx and Ptx. Also in this case, the inhibitory effect did not depend on an increase of intracellular cAMP as indicated by NK cell treatment with FSK, IBMX, or both. Further evidence of the involvement of G-proteins in LFA-1-mediated signal transduction was the inhibitory effect of the GDP analog guanosine-5'-O-2-thiodiphosphate (GDP beta S) on LFA-1-mediated calcium mobilization. Taken together, our data provide evidence that the LFA-1-mediated NK cell adhesion and signal transduction are partially independent phenomena which may be regulated by different G-proteins.

Adenylate Cyclase Toxin↗
PubMed1996

Development in vitro of human CD4+ thymocytes into functionally mature Th2 cells. Exogenous interleukin-12 is required for priming thymocytes to produce both Th1 cytokines and interleukin-10.

Fresh postnatal thymocyte cell suspensions were directly cloned under limiting dilution conditions with either phytohemagglutinin or toxic shock syndrome toxin-1 (TSST-1), a bacterial superantigen. Cultures contained allogenic irradiated feeder cells and interleukin (IL)-2, in the absence or presence of exogenous IL-4, interferon (IFN)-gamma or IL-12. The resulting CD4+ T cell clones generated under these different experimental conditions were then analyzed for their ability to produce IL-2, IL-4, IL-5, IL-10, IFN-gamma and tumor necrosis factor (TNF)-beta in response to stimulation with phorbol 12-myristate 13-acetate (PMA) + anti-CD3 monoclonal antibody or PMA + ionomycin. Different from T cell clones generated from peripheral blood, virtually all CD4+ T cell clones generated from human thymocytes produced high concentrations of IL-2, IL-4 and IL-5, but no IFN-gamma, TNF-beta or IL-10. Moreover, after activation, these clones expressed on their surface membrane both CD30 and CD40 ligand, but not the product of lymphocyte activation gene (LAG)-3, and provided strong helper activity for IgE synthesis by allogeneic B cells. The Th2 cytokine pattern could not be modified by the addition of IFN-gamma. However, upon addition of exogenous IL-12, the resulting CD4+ thymocyte clones produced TNF-beta, IFN-gamma, and IL-10 in addition to IL-4 and IL-5. These results suggest that CD4+ human thymocytes have the potential to develop into cells producing the Th2 cytokines IL-4 and IL-5, whereas the ability to produce both Th1 cytokines and IL-10 is acquired only after priming with IL-12.

CD4-Positive T-Lymphocytes↗
PubMed1996

Expression of human NKRP1A by CD34+ immature thymocytes: NKRP1A-mediated regulation of proliferation and cytolytic activity.

In this study, we show that NKRP1A is expressed and functions on a subset of immature human thymocytes. We took advantage of the monoclonal antibody (mAb) 191B8 that was obtained by immunizing mice with cultured human thymocytes characterized by an immature surface phenotype [CD2- CD3- CD4- CD8- stem cell factor receptor (SCFR)+] and expressing cytoplasmic CD3 epsilon chain. The 191B8 antibody homogeneously reacted with the immunizing population but not with most unfractionated thymocytes. It stained a minor population of resting immature thymocytes co-expressing CD34, SCFR, or both. Following culture of the CD34+ or CD34- fractions of CD2- CD3- CD4- CD8- purified immature thymocytes with recombinant interleukin-2 (rIL-2), the 191B8-defined antigen was expressed on virtually all cells even when 191B8+ cells were removed from the starting population. On the other hand, no 191B8+ cells were detected in fresh or cultured thymocytes expressing a more mature phenotype. Biochemical analysis of 191B8 mAb-reactive molecules revealed, under non-reducing conditions, two bands displaying apparent molecular masses of 80 and 44 kDa and a single band of 44 kDa under reducing conditions. Digestion with proteases indicated that the 80-kDa form represented a homodimeric form of two 44-kDa molecules, while deglycosylation with N-glycanase suggested the existence of four N-glycosylation sites. Transfection of COS7 or NIH3T3 cells with hNKRP1A cDNA showed that the 191B8 mAb recognized NKRP1A as shown by both immunofluorescence analysis and immunoprecipitation experiments. Functional studies showed that the 191B8/NKRP1A molecule mediated strong inhibition of the cytolytic activity of cultured CD2- CD3- immature thymocytes against a panel of tumor target cells. More importantly, 191B8 mAb induced proliferation of CD2- CD3- fresh thymocytes which was not increased by rIL-2. Thus, we propose that NKRP1A molecules, which are expressed in highly immature thymocytes, may play a regulatory role in their growth and function.

Antigens, CD34↗
PubMed1996

A novel surface molecule homologous to the p58/p50 family of receptors is selectively expressed on a subset of human natural killer cells and induces both triggering of cell functions and proliferation.

Human natural killer (NK) cells express inhibitory (p58) or activatory (p50) receptors for HLA-C alleles. Here, we describe a novel member of the p58/p50 family that is expressed by a subset of NK cells in about one third of donors. This molecule, termed p50.3, mediates NK cell triggering as revealed by the induction of intracellular free calcium mobilization, cytokine release and cytotoxicity. In addition, anti-p50.3 monoclonal antibody (mAb) induced a selective, strong proliferation of p50.3+ NK cells in peripheral blood lymphocytes. Although p50.3 molecules do not appear to display an obvious HLA class I specificity, they are usually coexpressed with known inhibitory receptors for HLA class I alleles, mAb-mediated cross-linking of these receptors leads to inhibition of the anti-p50.3 mAb-induced NK cell activation and proliferation. Surface p50.3 molecules are glycoproteins of approximately 55-58 kDa which, upon deglycosylation, display a relative molecular mass of 36 kDa, similar to that of deglycosylated (activatory) p50 receptors. Analysis of the two-dimensional peptide maps of the 50.3 molecules revealed a high homology with the other HLA-C-specific p58/p50 receptors. The use of a set of oligodeoxynucleotide primers, previously shown to amplify the activatory (p50) forms of HLA-C-specific receptors, consistently amplified in p50.3+ clones a cDNA sequence termed KKA3. This sequence belongs to the p58/p50 multigene family, that encodes for a transmembrane protein specifically stained by anti-p50.3 mAb in cell transfectants. Similar to p50 molecules, the KKA3-encoded molecules are characterized by two extracellular immunoglobulin-like domains, by the presence of a lysine in the transmembrane region and a short (39 amino acids) cytoplasmic tail which does not contain immune receptor tyrosine-based activation motifs (ITAM)-like sequences.

Amino Acid Sequence↗
PubMed1996

CD94 functions as a natural killer cell inhibitory receptor for different HLA class I alleles: identification of the inhibitory form of CD94 by the use of novel monoclonal antibodies.

CD94 molecules have been suggested to function as inhibitory natural killer cell (NK) receptors involved in the recognition of HLA-B alleles sharing the Bw6 supertypic specificity. In this study, we show that CD94 molecules may play a more general role: they are also involved in the recognition of other HLA class I molecules, including HLA-C and at least some HLA-A alleles. The inhibitory effect mediated by CD94 molecules on NK cytolytic activity is lower in magnitude than that of bona fide inhibitory receptors such as p58 or p70. Distinct from the other human NK receptors involved in HLA class I recognition, CD94 is expressed on virtually all NK cells. In addition, it has been shown to be functionally heterogeneous since, in different clones, CD94 mediated either cell triggering or inhibition. Although NK cells expressing inhibitory CD94 molecules are usually characterized by a CD94bright phenotype, there is no precise correlation between fluorescence intensity and inhibitory or activating function. Here, we describe two novel monoclonal antibodies (mAb) which selectively recognize inhibitory CD94 molecules and bind to a subset (variable in size among different donors) of CD94bright cells. The use of these mAb allows the direct assessment of NK cells expressing inhibitory CD94 receptors both at the population and at the clonal level.

Alleles↗
PubMed1996

The molecular basis of natural killer (NK) cell recognition and function.

Natural Killer cells are likely to play an important role in the host defenses because they kill virally infected or tumor cells but spare normal self-cells. The molecular mechanism that explains why NK cells do not kill indiscriminately has recently been elucidated. It is due to several specialized receptors that recognize major histocompatibility complex (MHC) class I molecules expressed on normal cells. The lack of expression of one or more HLA class I alleles leads to NK-mediated target cell lysis. Different types of receptors specific for groups of HLA-C, HLA-B, and, very recently, HLA-A alleles have been identified. While in most instances, they function as inhibitory receptors, an activatory form of the HLA-C-specific receptors has been identified in some donors. Molecular cloning of HLA-C-, HLA-B- or HLA-A-specific receptors has revealed new members of the immunoglobulin superfamily with two or three Ig-like domains, respectively, in their extracellular portion. While the inhibitory form is characterized by a long cytoplasmic tail associated with a non-polar transmembrane portion, the activatory one has a short tail associated with a Lys-containing transmembrane portion. Thus, these human NK receptors are different from the murine Ly49, that is a type II transmembrane protein characterized by a C-type lectin domain. A subset of activated T lymphocytes expresses NK-type class I-specific receptors. These receptors exert an inhibiting activity on T cell receptor-mediated functions and may provide an important mechanism of downregulation of T cell responses.

Antigen Presentation↗
PubMed1996

NK-cell receptors and recognition of MHC class I molecules.

Two families of natural killer (NK)-cell receptors exist that interact with major histocompatibility complex (MHC) molecules, thereby preventing cytotoxic cells from killing target cells. The expanding knowledge of these receptors provided the focus for a recent meeting.

Animals↗
PubMed1996

Physical and functional association of CD45 and CD3-TCR complex on CD1+ human thymocytes. Evidence that the engagement of CD45 molecules can prevent CD1+ thymocytes from apoptosis.

In this study the effects of CD45 engagement on CD3-TCR-driven stimulation of CD1+ human immature thymocytes have been analyzed. Simultaneous cross-linking of CD45 and CD3 antigens on highly purified CD1+ thymocytes reduced the number of cells undergoing apoptosis after 16 h of in vitro culture. This cell population might represent immature thymocytes committed in vivo to die by programmed cell death (PCD). CD45 engagement could also increase the number of cycling CD1+ thymocytes; of note, the large majority (> 95%) of dividing cells expressed the CD1 molecule at the cell surface, indicating that proliferating cells were actually represented by immature thymocytes. These data suggest that the CD45 molecule might play a role in the rescue of immature thymocytes from PCD during differentiation. Along this line, we found that activation of CD1+ thymocytes via the CD3-TCR complex could be enhanced by CD45, both in terms of transcription and surface expression of IL-2R. These effects might be explained by the finding that the CD45 molecule (but not its isoforms CD45RO and RA) was physically associated with the CD3-TCR complex at the cell surface of CD1+ human thymocytes, as shown by co-precipitation and co-capping experiments. Finally, cross-linking of CD45 and CD3 antigens led to the expansion of CD3+ thymocytes co-expressing CD4 and CD8, indicating that simultaneous engagement of CD45 and CD3 molecules can block CD1+ cells at the double-positive (CD3+CD4+CD8+) differentiation stage. On the other hand, stimulation through CD3 resulted in the expansion of thymocytes showing a mature phenotype (CD3+CD4+ or CD3+CD8+). Altogether, these findings suggest that the CD45 molecule is involved both in early activation and in the regulation of CD1+ thymocyte differentiation.

Antibodies, Monoclonal↗
PubMed1996

Treatment of stage IIIB non-small-cell lung cancer with surgery followed by infusion of tumor infiltrating lymphocytes and recombinant interleukin-2: a pilot study.

Stage IIIb non-small-cell lung cancer (NSCLC) has a poor prognosis. The median survival is approximately 6 months, and only 30% of patients are alive 1 year after diagnosis. The need for effective treatment is evident. The aim of this study was to evaluate whether the infusion of tumor-infiltrating lymphocytes (TILs), isolated from resected tumor, expanded in vitro and injected together with recombinant Interleukin-2, is feasible and may at least partially modify the poor prognosis in these patients. The infusion of TILs, derived from surgically resected NSCLC and expanded in vitro, together with subcutaneous (s.c.) injections of recombinant interleukin-2 (rIL-2) was attempted in a group of 11 patients. Treated patients were infused i.v. with in vitro expanded TILs (from 4 to 70 x 10(9) cells), and rIL-2 was injected s.c. at doses varying from 61 to 378 x 10(6) IU. Toxic side effects (fever and, in some cases, hypotension) were observed and limited the dose of rIL-2 infused. Follow-up was continued for 40 months. The mean survival time was 13.8 months. Three of five TIL-treated patients with residual disease have no evident disease after 1 year, and two of them are still alive and have no evidence of disease after 40 months. This pilot study suggests that the infusion of in vitro expanded TILs, derived from surgical samples, is feasible and seems to prolong overall survival and to control the residual disease in patients with advanced NSCLC.

Aged↗
PubMed1996

Receptors for HLA class-I molecules in human natural killer cells.

Natural killer cells are likely to play an important role in the host defenses because they kill virally infected or tumor cells but spare normal self-cells. The molecular mechanism that explains why NK cells do not kill indiscriminately has recently been elucidated. It is due to several specialized receptors that recognize major histocompatibility complex (MHC) class I molecules expressed on normal cells. The lack of expression of one or more class I alleles leads to NK-mediated target cell lysis. During NK cell development, the class I-specific receptors have adapted to self-class I molecules on which they recognize epitopes shared by groups of class I alleles. As such, they may fail to recognize either self-molecules that bound unusual peptides or allogeneic class I molecules unrelated to self-alleles. Different types of receptors specific for groups of HLA-C or HLA-B alleles have been identified. While in most instances, they function as inhibiting receptors, an activating form of the HLA-C-specific receptors has been identified in some donors. Molecular cloning of HLA-C- and HLA-B-specific receptors has revealed new members of the immunoglobulin superfamily with two or three Ig-like domains, respectively, in their extracellular portion. While the inhibiting form is characterized by a long cytoplasmic tail associated with a nonpolar transmembrane portion, the activating one has a short tail associated with a Lys-containing transmembrane portion. Thus, these human NK receptors are different from the murine Ly49 that is a type II transmembrane protein characterized by a C type lectin domain. A subset of cytolytic T lymphocytes expresses NK-type class I-specific receptors. These receptors exert an inhibiting activity on T cell receptor-mediated functions and offer a valuable model to analyze the regulatory mechanisms involved in receptor-mediated cell activation and inactivation.

Animals↗
PubMed1995

Existence of both inhibitory (p58) and activatory (p50) receptors for HLA-C molecules in human natural killer cells.

The natural killer (NK) cell-specific p58 molecules EB6 and GL183 have been shown to represent the putative surface receptors for two distinct groups of human histocompatibility leukocyte antigen (HLA) C alleles. Interaction between p58 receptors and class I molecules expressed on target cells results in inhibition of the NK-mediated cytolytic activity and thus in target cell protection. In the present study, we show that EB6 molecules may also act as receptors mediating NK cell triggering. Activatory EB6 molecules were found to be confined only to certain donors. Moreover, in these donors, only a fraction of EB6+ NK clones expressed the activatory form of EB6 molecules, while the remaining clones expressed the conventional inhibitory form. Biochemical analysis of the activatory EB6 molecules revealed a molecular mass of approximately 50 kD (p50), thus differing from the 58-kD inhibitory form. This difference was not due to differential glycosylation of the same protein, as revealed by deglycosylation experiments of isolated EB6 molecules. Treatment of purified p58 or p50/EB6 molecules with proteolytic enzymes, including V8-protease, chymotrypsin, and papain, showed only minor differences in the resulting peptides. Treatment with pepsin followed by two-dimensional peptide mapping demonstrated that, although the majority of peptides migrated in identical positions, differences between the two forms could be detected for at least one major peptide. Anti-EB6 monoclonal antibody (mAb)-mediated cross-linking of p50 molecules was required to trigger the cytolytic activity and the intracellular calcium ([Ca+2]i) increases in appropriate NK clones. Likewise, mAb-mediated cross linking of the p58 EB6 molecules was needed to inhibit the cytolytic activity; however, in this case, no [Ca+2]i increases could be detected. In NK clones expressing the inhibitory p58 EB6 receptors, soluble anti-EB6 mAb prevented recognition of protective Cw4 molecules and reconstituted target cell lysis. In contrast, in clones expressing the activatory p50/EB6 receptor, EB6 masking frequently resulted in partial inhibition of the cytolytic activity against Cw4+ target cells. Therefore, it appears that NK clones expressing the p50/EB6 receptors are induced to lyse Cw4+ target cells upon specific interaction with Cw4 molecules. This concept was further substantiated by experiments in which target cells were represented by the HLA-negative LCL721.221 cell line transfected with the Cw4 allele. Phenotypic and functional analysis of a large number of NK clones showed that clones expressing the activatory p50/EB6 molecules consistently coexpressed inhibitory receptors for other HLA class I alleles.(ABSTRACT TRUNCATED AT 400 WORDS)

Alleles↗
PubMed1995

Amino acid substitutions can influence the natural killer (NK)-mediated recognition of HLA-C molecules. Role of serine-77 and lysine-80 in the target cell protection from lysis mediated by "group 2" or "group 1" NK clones.

Natural killer (NK) cells have been shown to express a clonally distributed ability to recognize HLA class I alleles. The previously defined NK clones belonging to "group 1" recognize HLA-C*0401 (Cw4) and other HLA-C alleles sharing Asn at position 77 and Lys at position 80. Conversely, the "group 2" NK clones recognize HLA-Cw*0302 (Cw3) and other HLA-C alleles characterized by Ser at position 77 and Asn at position 80. We assessed directly the involvement of these two residues in the capacity of NK cell clones to discriminate between the two groups of HLA-C alleles. To this end, Cw3 and Cw4 alleles were subjected to site-directed mutagenesis. Substitution of the amino acids typical of the Cw3 allele (Ser-77 and Asn-80) with those present in Cw4 (Asn-77 and Lys-80) resulted in a Cw3 mutant that was no longer recognized by group 2 NK cell clones, but that was recognized by group 1 clones. Analysis of Cw3 or Cw4 molecules containing single amino acid substitutions indicates roles for Lys-80 in recognition mediated by group 1 clones and for Ser-77 in recognition mediated by group 2 clones. These results demonstrate that NK-mediated specific recognition of HLA-C allotypes is affected by single natural amino acid substitutions at positions 77 and 80 of the heavy chain.

Amino Acid Sequence↗
PubMed1995

Coexpression of two functionally independent p58 inhibitory receptors in human natural killer cell clones results in the inability to kill all normal allogeneic target cells.

In the present study, we define a group of natural killer (NK) clones (group 0) that fails to lyse all of the normal allogeneic target cells analyzed. Their specificity for HLA class I molecules was suggested by their ability to lyse class I-negative target cells and by the fact that they could lyse resistant target cells in the presence of selected anti-class I monoclonal antibodies. The use of appropriate target cells represented by either HLA-homozygous cell lines or cell transfectants revealed that these clones recognized all the HLA-C alleles. By the use of monoclonal antibodies directed to either GL183 or EB6 molecules, we showed that the EB6 molecules were responsible for the recognition of Cw4 and related alleles, while the GL183 molecules recognized Cw3 (and related C alleles). These data suggest that the GL183 and the EB6 molecules can function, in individual NK clones, as independent receptors for two different groups of HLA-C alleles, (which include all known alleles for locus C), thus resulting in their inability to lyse all normal HLA-C+ target cells. Indirect immunofluorescence and fluorescence-activated cell sorting analysis revealed that the presently defined GL183+EB6+ group 0 NK clones brightly express EB6 molecules (EB6bright) while the GL183+EB6+ group 2 clones (unable to recognize Cw4) express an EB6dull phenotype. These data also imply that the density of EB6 receptors may be critical for the generation of an optimal negative signal upon interaction with appropriate HLA-C alleles.

Cell Death↗
PubMed1995

p40, a novel surface molecule involved in the regulation of the non-major histocompatibility complex-restricted cytolytic activity in humans.

Four monoclonal antibodies (mAb) termed NKTA255, NKTA72, 1F1 and 1B1 were selected on the basis of their ability to inhibit the cytolytic activity of natural killer (NK) cell clones against P815 target cells. These mAb selectively reacted with normal or tumor cells of hematopoietic origin and displayed a cellular distribution similar to that of CD45 or CD11a/CD18 antigens. Immunoprecipitation experiments showed that they reacted with molecules with an apparent molecular mass of 40 kDa under both reducing and nonreducing conditions ("p40" molecules), thus differing from CD45 or CD11a/CD18 antigens as well as from the "inhibitory" receptors for HLA class I molecules (i.e. p58, CD94 and NKB1 molecules). Double-immunofluorescence analysis of peripheral blood mononuclear cells allowed the identification of three distinct populations on the basis of the fluorescence intensity of cells stained with anti-p40 mAb. p40bright cells were homogeneously HLA-DR-positive, p40medium cells were HLA-DR-negative but co-expressed CD56 antigens, while p40dull cells were all CD3+. Anti-p40 mAb strongly inhibited the lysis of K562 target cells, mediated by fresh NK cells, as well as the lysis of P815 target cells by NK or T cell clones. In addition, in redirected killing assays, anti-p40 mAb strongly reduced the anti-CD16 mAb-induced cytolytic activity of NK cell clones. On the contrary, they did not inhibit either the anti-CD3 or anti-T cell receptor mAb-mediated cytolytic activity of T cell clones or the lysis of allogeneic phytohemagglutinin blasts mediated by specific cytolytic T cell clones. The p40-induced inhibition of the NK cytotoxicity required optimal cross-linking, as anti-p40 mAb could inhibit the lysis of Fc gamma receptor (Fc gamma R)-positive but not of Fc gamma R-negative target cells. In addition, (Fab')2 fragments of anti-p40 mAb failed to inhibit the lysis of Fc gamma R-positive target cells. In conclusion, p40 molecules represent a new type of inhibitory surface molecule that appears to play a general regulatory role in the NK-mediated cytolysis.

Antibodies, Monoclonal↗
PubMed1995

Molecular clones of the p58 NK cell receptor reveal immunoglobulin-related molecules with diversity in both the extra- and intracellular domains.

Recognition of major histocompatibility class I molecules on target cells by natural killer (NK) cells confers selective protection from NK-mediated lysis. Cross-linking of the p58 NK receptor, involved in the recognition of HLA-C alleles, delivers a negative signal that prevents target cell lysis. Molecular cloning of the p58 NK receptor reported here revealed a new member of the immunoglobulin superfamily. Five distinct p58 receptors, with sequence diversity in the immunoglobulin-related domains, were identified in a single individual. All NK clones tested expressed at least one p58 member. Three different types of transmembrane and cytoplasmic domains exist, even among receptors with closely related extracellular domains. These data revealed a repertoire of NK cells with clonally distributed p58 receptors exhibiting diversity in both extracellular and intracellular domains.

Antibodies, Monoclonal↗