Rat Natural Killer Research Articles

Coexpression of NKR-P1 and alpha beta-TCR on lymphoid cells in fully xenogeneic (rat-->mouse) chimeras and syngeneically reconstituted (A-->A) rats.

Abstract We have identified three populations of cells among rat splenocytes expressing NKR-P1, including cells of NKR-P1bright/alpha beta-TCR-, NKR-P1dim/alpha beta-TCR+, and NKR-P1dim/alpha beta-TCR- phenotypes. To study the phenotypic characteristics and development of these various cell populations, we have made use of transplanting untreated rat bone marrow into recipient rats (syngeneic) or mice (fully xenogeneic) conditioned with total body irradiation. Rat NK cells exhibit normal phenotypic markers (NKR-P1+, CD8+) and are normally functional by 28 days after reconstitution. We have found that the various populations of NKR-P1+ cells are enriched significantly in the spleen and follow a characteristic pattern of development in the first mo after reconstitution. After syngeneic bone marrow reconstitution (rat-->rat), NKR-P1dim and NKR-P1bright cells (3-15%) can be demonstrated among splenocytes as early as day 3 after bone marrow transplantation. By day 7, the NKR-P1+ cells reach peak levels and comprise as much as 80% of splenic lymphoid cells, with 35% being NKR-P1bright and 45% being NKR-P1dim. The percentage of NKR-P1+ cells decreases over the next several wk until they constitute "normal rat" levels with 8 to 20% being NKR-P1bright and only 1 to 5% being NKR-P1dim. These same populations are also present in fully xenogeneic chimeras. In both models, approximately 80 to 90% of the NKR-P1dim cells were found to coexpress alpha beta-TCR at all time points. These NKR-P1dim/alpha beta-TCR+ cells are not large granular lymphocytes and lack NK cell lytic activity against YAC-1 target cells. Additional analyses of cells derived from spleen, bone marrow, and thymus indicated that NKR-P1+ cells develop, for the most part, in a thymic-independent manner in our fully xenogeneic chimeras and syngeneically reconstituted rats. At present the developmental pathway of these NKR-P1dim cells remains speculative.

CD45-negative mutants of a rat natural killer cell line fail to lyse tumor target cells.

To examine the role of CD45 in NK cell activation, we isolated three mutants and one variant of a rat NK cell line, RNK-16. Each of these lacked cell-surface expression of CD45 and did not have detectable transcripts for CD45 on Northern blot analysis. The CD45-negative cells expressed CD2, CD53, and NKR-P1, but mAb-induced perturbations of these molecules did not induce protein tyrosine phosphorylations and increases in the concentration of cytoplasmic-free calcium, as occurred in the wild-type RNK-16. Unlike the wild-type cells, the CD45-negative cells failed to lyse YAC-1 and RL-male-1 tumor targets. The cytolytic activity of the CD45-negative cells could be stimulated pharmacologically by ionomycin and PMA, which, when added to the cytotoxicity assays, induced killing of tumor targets. These studies suggest that CD45 is required for the response of RNK-16 cells to target cells and for signaling through CD2, CD53, and NKR-P1.

Comparison of the effects of (±) CP 96,345 and L-668,169 on neurokinin receptor mediated responses in rat and guinea-pig isolated tissues

The effects of (±) CP 96,345 and L-668,169 on NK 1-, NK 2- and NK 3-receptor mediated contractile responses were compared in guinea-pig and rat isolated smooth muscle tissues. Both (±) CP 96,345 and L-668,169 inhibited NK 1-mediated responses in guinea-pig ileum (pA 2 = 9.3 and 6.4 respectively) but not in rat bladder (pK B = < 6 and < 5.5 respectively) consistent with species differences in NK 1-receptor pharmacology. Both compounds showed some selectivity in inhibiting NK 1-receptor evoked responses in guinea-pig ileum compared to their inhibitory effects on NK 2-receptor mediated responses in guinea-pig bladder and rat ileum and NK 3-mediated responses in guinea-pig ileum and rat portal vein.

Immunopurification of Functional Asp-ase (Natural Killer Cell Granzyme B) Using a Monoclonal Antibody

Enzymatically active granule-associated serine protease ("granzyme") B has been purified from human NK cell lysates, using novel granzyme B-specific monoclonal antibodies. Two antibodies, designated 2C5 and 1D10, were produced following immunization of BALB/c mice with a nineteen amino acid peptide synthesized according to the sequence deduced from a granzyme B cDNA clone. Of several peptide-reactive culture supematants that resulted from cell fusion of splenocytes with NS-1 myeloma cells, clones 2C5 (IgG2a) and 1D10 (IgG1) produced antibodies which detected a ∼32kDa molecule in human NK cell lysates by Western blotting. This reactive species was detectable in lysates of IL-2-stimulated peripheral blood mononuclear cells, the human NK leukemia cell line YT, the rat NK leukemia cell line RNK-16, but not in the mouse cytotoxic T cell line CTLL-R8 or a variety of non-cytolytic hemopoietic tumor cell lines. The specificity of reactivity with granzyme B was demonstrated by the reaction of the monoclonal antibody with active granzyme in the lysate of COS-7 cells iransfected with human granzyme B cDNA, but not with granzyme H expressed in an identical fashion. Western blotting on Percoll-fractionated IL-2 activated human peripheral blood lymphocyte lysates and YT demonstrated reactivity of the monoclonal antibody with a ∼32kDa species only in those fractions with granzyme A (BLT esterase) and B (Asp-ase) activities. Moreover, 2C5/1D10 antibodies coupled to Protein A-sepharose beads immunoprecipitated enzymatically active granzyme B from YT cell lysates. Scale up of this procedure should yield a means of purifying the large quantities of natural or recombinant granzyme B required to study the function of this granzyme in cellular cytotoxicity.

Natural killer cell depletion and diabetes mellitus in the BB/Wor rat (revisited)

The BB/Wor diabetes-prone rat is an animal model of human insulin-dependent diabetes mellitus. In this model of spontaneous autoimmunity, natural killer cells are candidate cytotoxic effector cells, believed to be the mediators of beta-cell cytolysis in vivo. We therefore studied the effects of an anti-natural killer cell monoclonal antibody on the spontaneous development of diabetes in the BB/Wor rat. The 3.2.3 monoclonal antibody recognizes a molecular present on rat natural killer cells and selectively depletes these cells in vivo. Chronic treatment of diabetic-prone rats with 3.2.3 monoclonal antibody cleared circulating phenotypic natural killer cells, depleted in vitro spleen natural killer cell function, and profoundly reduced intra-islet accumulation of 3.2.3+ cells, but did not prevent or delay the onset of diabetes. These results indicate that natural killer cells are not necessary for the development of spontaneous diabetes in BB/Wor rats.

Degradation of Enkephalins by Rat Lymphocyte and Purified Rat Natural Killer Cell Surface Aminopeptidases

Enkephalins have been reported to induce an elevation in natural killer (NK) cell cytolytic function. In the central nervous system, the short-lasting biological activity of the enkephalins may be attributable to their rapid hydrolysis at the cell surface. In a similar manner, a potential mechanism for regulating the effects of enkephalins on NK cells is through their degradation at the cell surface. The purpose of this study was to determine if NK cells were capable of enzymatically degrading Met- and Leu-enkephalin and to determine the type(s) of enzymes responsible. We report that rat nylon wool enriched splenocytes, purified NK cells, and interleukin-2 activated NK (A-NK) cells were capable of hydrolyzing the N-terminal Tyr residue from Met- and Leu-enkephalin as determined by high-performance liquid chromatography. The rate of Tyr cleavage from Met-enkephalin was approximately twice that of Leu-enkephalin for both splenocytes, NK, and A-NK cells. On a cellular basis, enkephalin degradation was four to five times greater with A-NK cells than with splenocytes. Only a Tyr cleavage product was detected, which suggested the possibility of an aminopeptidase activity. This was confirmed by the ability of bestatin, a specific inhibitor of cell surface aminopeptidases, to almost completely inhibit enkephalin degradation by splenocytes (85%) and A-NK cells (96%). A-NK cells were more sensitive to bestatin inhibition as indicated by their IC50 values (0.01 m M for splenocytes and 0.001 m M for A-NK cells). In addition, the chelator 1, 10-phenanthroline was also capable of effectively inhibiting enkephalin degradation, suggesting that the enzyme responsible has the characteristics of a metalloprotease. In contrast to the effects of bestatin or phenanthroline, typical inhibitors of serine and thiol proteases were without effect.

Rat class III Fc gamma receptor isoforms differ in IgG subclass-binding specificity and fail to associate productively with rat CD3 zeta.

Several new rat class III Fc gamma R isoforms are described here, extending the genetic complexity of this receptor family and further distinguishing rat CD16 from mouse CD16, represented by only one receptor isoform, and human CD16, represented by only two isoforms. RNase protection assays reveal that three rat tumor cell lines--RBL-1 basophilic leukemia cells, RM-SV1 macrophages, and CRNK-16 NK cells--all coordinately express multiple and probably identical rtFc gamma RIII-related transcripts in similar relative proportions but at significantly different levels. These results indicate that no single isoform predominates in these cell types but that the overall level of rtFc gamma RIII-related transcripts is differentially regulated. Two of the rtFc gamma RIII isoforms found to have extensive amino acid sequence differences in their second extracellular (EC2) domains are shown to bind rat and mouse IgG subclasses differently. This result suggests that the receptor isoform diversity in this species may function as a mechanism for extending the IgG-binding capacity of rat leukocytes. Cloned cDNA for the rat CD3 zeta protein was also isolated in this study and its ability to augment surface expression of class III Fc gamma R was tested by rosetting of cDNA-transfected COS cells. Like the structurally homologous mouse CD3 zeta, rat CD3 zeta fails to promote surface expression of Fc gamma RIII, sharply contrasting the efficient receptor expression produced by human CD3 zeta. Variations in the transmembrane amino acid sequences correlate with the divergent capacities of these CD3 zeta molecules to augment receptor expression. The high levels of CD3 zeta message expressed in rat NK cells may indicate that other unidentified hetero-subunits are required for assembly of rat CD3 zeta into functional CD16 receptors.

Involvement of Phospholipase A 2 Activation and Arachidonic Acid Metabolism in the Cytotoxic Functions of Rat NK Cells

Arachidonic acid (AA) release via phospholipase A 2 (PLA 2) activation and generation of eicosanoids have been implicated as playing signaling roles in a variety of cell types. Here we show evidence that interaction of fresh NK cells with membranes from sensitive or antibody (Ab)-coated targets generates eicosanoids through both cycloxygenase (CO) and lipoxygenase (LO) pathways. Eicosanoid generation is attributable to PLA 2 activation since pretreatment with PLA 2 irreversible inhibitors, such as mepacrine or parabromophenacylbromide (pBPB), completely blocks AA metabolite generation. The involvement of PLA 2 or AA metabolites in the cytotoxic functions of rat NK cells has also been investigated. Treatment of effector cells with mepacrine or pBPB resulted in complete, irreversible, dose-dependent inhibition of both NK and ADCC activities, which were completely reversed by the addition of exogenous PLA 2 or its hydrolysis products, AA and lysophosphatidylcholine (lysoPC). Among the metabolites of AA released by NK cells, the 5-LO product leukotriene B 4 (LTB 4) seems to play an important role in cytolytic activities of NK cells. Indeed, the LO inhibitor, nordihydroguaiaretic acid (NDGA), totally abrogated both NK and ADCC activities, which were restored by the addition of exogenous LTB 4. However, the failure of LTB 4 to reverse mepacrine or pBPB-induced inhibition of NK and ADCC suggests that its effects could be mediated by PLA 2. The results are consistent with a crucial role for the target-stimulated AA release as a fundamental step in the signal transduction pathway in NK cell. Moreover, LTB 4 generation seems to be responsible for further PLA 2 activation in a second step leading to the amplification of response.

Differences in the pharmacological binding profile of rat and human NK 2 tachykinin receptors

Differences in the pharmacological binding profile of rat and human NK 2 tachykinin receptors

Interaction of the substance P receptor antagonist RP 67580 with the rat brain NK 1 receptor expressed in transfected CHO cells

In the present study, we describe the effects of RP 67580, a substance P non-peptide antagonist, in binding and second messenger experiments performed using transfected Chinese hamster ovary cells expressing the rat NK 1 receptor. The cDNA sequence encoding the rat brain substance P receptor was transfected in Chinese hamster ovary cells, and cellular clones which stably express the corresponding protein were isolated. [ 3H]Substance P binding was performed in homogenates of these transfected cells and revealed the presence of NK 1 receptors in displacement experiments, using peptide analogs of three mammalian tachykinins (substance P, neurokinin A, neurokinin B). Scatchard analysis indicated a K d value of 0.33 ± 0.13 nM and a B max value of 5.83 ± 1.16 pmol/mg of protein. RP 67580, a selective NK 1-receptor antagonist was found to displace the specific binding of [ 3H]substance P. When [ 3H]RP 67580 was used as a ligand, it displayed a high affinity (K D value: 1.22 ± 0.27 nM) in transfected cell homogenates and only competed with NK 1 receptor ligands. Substance P stimulated the hydrolysis of phosphoinositide in a time- and concentration-dependent manner and this effect was mimicked by selective agonists of the NK 1 receptor ([Pro 9]SP and septide). RP 67580 did not induce any accumulation of inositol phosphates, but was found to inhibit the inositol phosphate increase mediated by substance P, without affecting the maximal response. From these results, one may conclude that the receptor expressed by the transfected Chinese hamster ovary cells revealed similar binding characteristics as the NK 1 receptor present in the rat brain and also confirmed the high affinity and the antagonist properties of RP 67580.

Identification of a vimentin-like function associated molecule (FAM) on rat NK cells: evidence for receptor function.

Monoclonal antibody (MoAb) 5C6 specifically binds to fish, rat and human NK cells and inhibits cytotoxicity. The molecule recognized by this MoAb is a 50-53-kDa membrane protein on rat leukaemic NK (CRC) cells. In the present study, we have obtained a partial internal amino acid sequence from a purified 42-kDa fragment of the CRC-function associated molecule (FAM). Three tryptic peptide fragments were sequenced and each showed homology to intermediate filament vimentin sequences as deduced from (GenBank) mouse cDNA sequences. Amino acid composition analysis indicated that similar to cytoskeletal vimentin, the FAM contained a high percentage of non-polar amino acids. To further assess the similarities between this protein and vimentin, two commercially available anti-vimentin MoAbs and one anti-vimentin polyclonal antibody were tested for binding and inhibition of NK cytotoxicity. All anti-vimentin MoAbs inhibited killing by rat NWNA cells of appropriate targets. Anti-vimentin MoAb 13.2 bound to 41% of NWNA cells compared with approximately 58% binding for MoAb 5C6. Capping and sequential binding experiments showed that MoAb 5C6 effectively removed, from CRC-cell membranes, the protein recognized by MoAb V9. Sequential addition of these two MoAbs (MoAb 13.2 followed by MoAb V9) to CRC cells did not produce competitive binding. Biochemical and Western blot analysis of the vimentin-like protein obtained from CRC cells indicated that this protein has a molecular weight of 48-50 kDa, with an isoelectric point of pH 6.1-6.3. This protein is cross-reactive by Western blot analysis with anti-vimentin and anti-intermediate filament (IFA) antigen MoAbs but not with anti-desmin or anti-actin MoAbs. The molecular weight heterogeneity (43 versus 48-50 kDa) of the CRC protein was also examined. Western blot analysis of the CRC extract after different in vitro incubation times at 37 degrees C and 4 degrees C demonstrated that the 50-53-kDa 'native' protein degraded to a 42-kDa protein by 24 and 48 h respectively. This degradation was inhibitable by 10 mM EGTA. Evidence is presented which indicates that a vimentin-like protein on transformed rat NK cells may be an antigen binding receptor which initiates target cell lysis.

CHARACTERIZATION OF MATURATION AND FUNCTION OF NATURAL KILLER CELLS IN XENOGENEIC (RAT ± MOUSE) BONE MARROW CHIMERAS

Reconstitution of B10 recipient mice, conditioned with total body irradiation (950 rads), with 40 x 10(6) untreated F344 or WF rat bone marrow cells results in stable rat stem-cell engraftment with multilineage lymphohematopoietic chimerism. We have now characterized NK cell generation, maturation, and function in fully xenogeneic chimeras (WF rat-->B10 mouse; F344-->B10 mouse). Early during xenogeneic reconstitution, rat-derived NK cells predominated in splenic lymphoid tissue, composing 14-18% of total cells at week 1 and increasing to 35.6-59.9% of total cells at week 2. By week 6, levels of rat NK cells had decreased and stabilized to that expected for normal rat (9-14.2%). The NK chimerism was reliably stable for up to 7 months following reconstitution. Most importantly, rat-derived NK cells were functional in both YAC tumor cytolysis and ADCC assays, suggesting that the xenogeneic mouse host environment was sufficient to support the generation, maturation, and function of rat-derived NK cells.

Association of Src-like protein tyrosine kinases with the CD2 cell surface molecule in rat T lymphocytes and natural killer cells.

The cell surface molecule CD2 has a signaling role in the activation of T lymphocytes and natural killer cells. Because perturbation of CD2 leads to the appearance of tyrosine-phosphorylated proteins, we investigated the possibility that CD2 associates with cytoplasmic protein tyrosine kinases. As determined by in vitro kinase assays and phosphoamino acid analysis, protein tyrosine kinase activity coprecipitated with CD2 from rat T lymphocytes, T lymphoblasts, thymocytes, interleukin-2-activated natural killer cells, and RNK-16 cells (a rat natural killer cell line). In each case, both p56lck and p59fyn were identified in the CD2 immunoprecipitate. In the thymus, the association between CD2 and these kinases occurred predominately in a small subset of thymocytes that had the cell surface phenotype of mature T cells, indicating that the association is a regulated event and occurs late in T-cell ontogeny. The finding that CD2 is associated with p56lck and p59fyn in detergent lysates suggests that interactions with these Src-like protein kinases play a critical role in CD2-mediated signal transduction.

Purification and cloning of a novel serine protease, RNK-Met-1, from the granules of a rat natural killer cell leukemia.

We have purified a 30-kDa serine protease (designated RNK-Met-1) from the granules of the rat large granular lymphocyte leukemia cell line (RNK-16) that hydrolytically cleaves model peptide substrates after methionine, leucine, and norleucine (Met-ase activity). Utilizing molecular sieve chromatography, heparin-agarose, chromatography, and reverse-phase high pressure liquid chromatography, RNK-Met-1 was purified to homogeneity and 25 NH2-terminal amino acids were sequenced. By using the polymerase chain reaction, oligonucleotide primers derived from amino acids at position 14-25 and from a downstream active site conserved in other serine protease genes were used to generate a 534-base pair cDNA clone encoding a novel serine protease from RNK-16 mRNA. This cDNA clone was used to isolate a full-length 867-base pair RNK-Met-1 cDNA from an RNK-16 lambda-gt11 library. The open reading frame predicts a mature protein of 238 amino acids with two potential sites for N-linked glycosylation. The cDNA also encodes a leader peptide of at least 20 amino acids. The characteristic Ile-Ile-Gly-Gly amino acids of the NH2 terminus and the His, Asp, and Ser residues that form the catalytic triad of serine proteases were both conserved. The amino acid sequence has less than 45% identity with any other member of the serine protease family, indicating that RNK-Met-1 is distinct and may itself represent a new subfamily of serine proteases. Northern blot analysis of total cellular RNA detected a single 0.9-kilobase mRNA in the in vitro and in vivo variants of RNK-16 and in spleen-derived plastic-adherent rat lymphokine-activated killer cells. RNK-Met-1 mRNA was not detectable in freshly isolated rat splenocytes, thymocytes, brain, colon, and liver or activated nonadherent rat splenocytes and thymocytes. These data indicate that RNK-Met-1 is a serine protease with unique activity that is expressed in the granules of large granular lymphocytes.

Association of Src-like protein tyrosine kinases with the CD2 cell surface molecule in rat T lymphocytes and natural killer cells.

The cell surface molecule CD2 has a signaling role in the activation of T lymphocytes and natural killer cells. Because perturbation of CD2 leads to the appearance of tyrosine-phosphorylated proteins, we investigated the possibility that CD2 associates with cytoplasmic protein tyrosine kinases. As determined by in vitro kinase assays and phosphoamino acid analysis, protein tyrosine kinase activity coprecipitated with CD2 from rat T lymphocytes, T lymphoblasts, thymocytes, interleukin-2-activated natural killer cells, and RNK-16 cells (a rat natural killer cell line). In each case, both p56lck and p59fyn were identified in the CD2 immunoprecipitate. In the thymus, the association between CD2 and these kinases occurred predominately in a small subset of thymocytes that had the cell surface phenotype of mature T cells, indicating that the association is a regulated event and occurs late in T-cell ontogeny. The finding that CD2 is associated with p56lck and p59fyn in detergent lysates suggests that interactions with these Src-like protein kinases play a critical role in CD2-mediated signal transduction.

Novel peptidomimetics: inhibitors of substance P endopeptidase

The synthesis of the novel bis-phenylalanine mimetic 1 and its incorporation into substance P are described. The key step in the synthesis of 1 is a Julia olefination reaction resulting in a trans-olefin. The synthesized compounds were able to inhibit a human substance P endopeptidase but lacked appreciable affinity for the rat NK 1-receptor.

Nongranular proteolytic enzymes of rat IL-2-activated natural killer cells. I. Subcellular localization and functional role.

Our investigations indicate that a variety of neutral serine proteases exist in highly purified, IL-2-activated rat NK (A-NK) cells. These enzymatic activities are not restricted to only cytolysin-containing granules and are not defined by only the assay of N-alpha-benzyloxycarbonyl-L-lysine thiobenzylesterase activity. These activities, which we term A-NKP 1, A-NKP 2, A-NKP 3, and A-NKP 4, cleave, respectively, the following fluorogenic peptide substrates: Boc-Phe-Ser-Arg-7-amino-4-methylcoumarin (AMC, trypsin-like); Suc-Ala-Ala-Phe AMC (chymotrypsin-like); Suc-Gly-Pro-Leu-Gly-Pro AMC (collagenase-like), and Z-Phe-Arg AMC (another trypsin-like enzyme). The proteases A-NKP 1, A-NKP 2, and A-NKP 3 are not cell surface-associated and appear to be cytosolic as defined by isopycnic sucrose density gradient centrifugation. In contrast, A-NKP 4 appears to be located in lysosomes. Treatment of rat A-NK cells with protease inhibitors that inhibit A-NKP 2 and A-NKP 3 also substantially inhibit A-NK cell-mediated cytotoxicity against both NK-sensitive and -resistant targets (YAC-1 and P815, respectively). These results indicate that A-NKP2 and A-NKP 3 may play a role in IL-2-activated NK cell-mediated cytotoxicity. A variety of proteolytic enzymes, in addition to granzymes, therefore exist in A-NK cells. Our studies indicate that a prerequisite to a thorough understanding of the role of proteases in killer cell function is the investigation of several classes of enzymes in addition to granzymes contained in lytic granules.

Stromal cells derived from spleen or bone marrow support the proliferation of rat natural killer cells in long-term culture.

Rat nylon wool nonadherent bone marrow cells were propagated for up to 75 days in co-culture with stromal cells derived from either spleen or bone marrow. Interleukin (IL) 1 enhanced the ability of spleen stroma to support the long-term culture of natural killer (NK) cells, ostensibly by inducing these support cells to synthesize other cytokines. Flow cytometry studies indicated that the nylon wool separation procedure enriched the concentrations of mature NK cells from 7.9% to 38.1% for splenocytes and from 3.8% to 19.5% for bone marrow cells. Analyses of the adherent zones of suspended nylon screen NK cell cultures revealed substantial numbers of large granular lymphocytes that expressed NK 323+/MOM/3F12/F2- phenotypes. The presence of both mature and immature cells of the NK lineage in this matrix was inferred by the presence of both IL-2 receptor (IL-2R) positive and IL-2R negative, and OX-8+ and OX-8- NK 323+ cells over the greater than 4-month experimental period. Suspended nylon screen cultures displayed a greater potential for producing cytolytic cells than either co-cultures of bone marrow nonadherent cells on stroma monolayers or suspension cultures. The large granular lymphocytes produced in suspended nylon screen cultures could be transformed into active killers of YAC-1 targets by IL-2. In contrast to bone marrow nonadherent cells, more splenic nylon-wool-passed cells displayed a mature NK phenotype, but their proliferative potential and ability to be transformed into cytolytic cells by IL-2 decreased rapidly in culture. In the suspended nylon screen culture system, NK cells migrate from the underlying stroma in stages as they mature, retain their cytolytic potential, and manifest a capacity for self-renewal. Cultured cells were routinely dissociated into single cell suspensions via enzyme treatment and were reinoculated onto "fresh" nylon screen/stromal cell templates after passage through nylon wool columns. These co-cultures continued to generate cytolytic cells in numbers greater than those of the initial inoculum.

Functional heterogeneity between NKR-P1bright/Lycopersicon esculentum lectin (L.E.)bright and NKR-P1bright/L.E.dim subpopulations of rat natural killer cells.

In this report, we present data on heterogeneity of rat NK cells utilizing a combination of antibody and lectin-binding characteristics. Among NKR-P1bright NK cells, two discrete populations characterized as Lycopersicon esculentum lectin (L.E.)bright (60 to 80%) and L.E.dim (20 to 40%) were identified by flow cytometry. Comparison of the morphology of sorted NKR-P1bright/L.E.bright and NKR-P1bright/L.E.dim cells indicated that both were greater than 90% LGL. An analysis of the functional capabilities of the sub-populations indicated that NKR-P1bright/L.E.bright NK cells were more efficient in lysis of YAC-1 target cells (1743 LU20/10(7) cells) than were NKR-P1bright/L.E.dim cells (504 LU20/10(7) cells). Conversely, NKR-P1bright/L.E.dim NK cells were much more efficient at lysis of antibody-sensitized erythrocytes (antibody-dependent cellular cytotoxicity (ADCC)) (1412 LU20/10(7) cells) than were NKR-P1bright/L.E.bright cells (165 LU20/10(7) cells). Lysis of antibody sensitized P815 target cells yielded similar results as NKR-P1bright/L.E.dim cells and NKR-P1bright/L.E.bright cells had 905 LU20/10(7) and 189 LU20/10(7), respectively. Additional experiments indicated that NKR-P1bright/L.E.bright NK cells had the capacity to trigger lytic activity via NKR-P1 whereas NKR-P1bright/L.E.dim NK cells did not. NKR-P1bright/L.E.bright sorted cells had a greater capacity to form conjugates with YAC-1 target cells than did NKR-P1bright/L.E.dim sorted cells. Conversely, NKR-P1bright/L.E.dim NK cells were demonstrated to form E-A rosettes whereas the NKR-P1bright/L.E.bright NK cells were not. Additional experiments indicated that tomato lectin itself was not responsible for the differences in reverse ADCC activity or ADCC activity among the subsets. However, lysis of YAC-1 target cells was modulated to some degree by the lectin. These data indicate that NKR-P1bright/L.E.bright and NKR-P1bright/L.E.dim subpopulations of rat NK cells have different capacities for: 1) triggering through NKR-P1; and 2) E-A rosette formation and lysis of antibody-sensitized target cells by ADCC.

A function-associated molecule on rat natural killer cells identified by anti-idiotypic monoclonal antibodies

Monoclonal antibodies were generated against idiotopes on an NK target antigen-specific IgM monoclonal antibody (mab). This mab (18C2) was originally produced against (NC-37) human EBV-transformed B cells. The 18C2 mab inhibits natural killer cell lysis of NC-37 and other target cells by preventing conjugate formation. Anti-18C2(id) mabs were tested for binding to effector cells and screened by ELISA, flow cytometry, and by inhibition of NK cytotoxicity. Two of the anti-18C2(id) (anti-id) mabs (12H1.C5 and 6D9.B11) were chosen for further study. The idiotypic specificity of these anti-id mabs was confirmed by testing their binding to 18C2 hybridoma cells in the presence of homologous and heterologous “cold” inhibitor mabs. Experiments were also conducted to determine the functional properties of these mabs. Anti-18C2(id) mab 12H1.C5 inhibited the cytotoxic activity of rat splenic NK (nylon wool nonadherent cells, NWNA) and rat ALAK cells. Flow cytometric (FCM) analysis of the binding of the anti-18C2(id) mabs demonstrated that mab 12H1.C5 bound 75.43% rat NWNA spleen cells, 43.74% rat ALAK cells, and 74.33% rat CRC − cells. Anti-id mab 6D9.B11 bound 45.20% NWNA cells, 70.45% rat ALAK cells, and 55.86% CRC − cells. Two-color FCM analysis demonstrated that the anti-id mabs not only bound to the same molecule on NK cells, but also these mabs bound to the same molecule as 5C6, an anti-NK. cell mab. Biochemical analysis of the antigen recognized by mab 12H1.C5 was determined by Western blotting. The determinant on NWNA cells recognized by mab 12H 1.C5 had an M r, of 40 kDa and appeared to be identical to that recognized by mab 5C6. The same experiment using a transformed rat RNK-16 (CRC −) cell extract and Western blot analysis, demonstrated an M r of 42 and 48 kDa in the presence of mabs 5C6 and 12H1.C5. Monoclonal antibody 5C6 was previously shown to recognize a vimentin-like function-associated molecule on NK cell membranes. The anti-id mabs were also shown to have cross-reactivity with the intermediate filament vimentin as determined by Western blot analysis.