Quantitative analysis of rod-cored vesicles and dense granules of large granular lymphocytes in the liver, spleen, and peripheral blood of rats

Large granular lymphocytes (LGL) comprise a natural defense system in the liver and exert an inhibitory effect on tumor cell metastasis. In order to demonstrate the maturation of LGL in the liver from the morphological aspect, we evaluated electron-microscopically the frequency of 0.2 micron vesicles (rod-cored and "empty" vesicles) and dense granules in LGL from the liver, spleen, and peripheral blood of the rat. Both of these cell organelles are characteristic to LGL and may relate to natural killer-mediated cytolysis. On the average, there were 12.7 of the 0.2 micron vesicles and 4.3 rod-cored vesicles (RCV) per cell section in the liver, 6.6 0.2 micron vesicles and 1.6 RCV in the spleen, and 8.6 0.2 micron vesicles and 0.9 RCV in the peripheral blood. The number of 0.2 micron vesicles per cell section ranged from 0 to 19 with the exception of a few higher instances. Therefore, LGL were divided into vesicle-rich (> 9 0.2 micron vesicles per cell section) and vesicle-poor (< 8 per cell section) populations. Hepatic LGL consisted mainly of a vesicle-rich population while splenic LGL consisted mainly of a vesicle-poor population, and peripheral blood contained equal proportions of both populations. In addition to diversity with regard to the number of 0.2 micron vesicles, LGL obtained from various organs also displayed heterogeneity in the number and size of dense granules.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of the NK-TR gene is required for NK-like activity in human T cells

NK cells lyse target cells without previous immune sensitization. A small subset of T cells also exhibits NK-like activity, which is distinct from TCR-mediated, MHC-restricted, and MHC-unrestricted cytotoxicity. We recently cloned a gene, NK-TR, which is postulated to be part of the NK target-recognition/triggering complex. To determine whether the NK-TR gene product is requisite for NK-like killing, stable antisense transfectants were generated by using a human T cell clone with NK-like activity. Two distinct antisense regions of the sequence were used to generate the transfectants alpha NK-TR and alpha Cyclo. Transfectants lost the ability to lyse NK-sensitive targets but did not lose lectin-mediated cytotoxic activity. This effect was not seen with the control vector transfectant cell line. The loss of NK-like activity by the antisense transfectant alpha NK-TR correlated with the specific decrease in endogenous NK-TR mRNA and protein. These results demonstrate the requirement for the NK-TR protein for NK-like killing. Moreover, the results have important implications for examining developmental relationship between T and NK cells and the possible roles for T cells with NK-like activity in vivo.

Expression of the NK-TR gene is required for NK-like activity in human T cells

NK cells lyse target cells without previous immune sensitization. A small subset of T cells also exhibits NK-like activity, which is distinct from TCR-mediated, MHC-restricted, and MHC-unrestricted cytotoxicity. We recently cloned a gene, NK-TR, which is postulated to be part of the NK target-recognition/triggering complex. To determine whether the NK-TR gene product is requisite for NK-like killing, stable antisense transfectants were generated by using a human T cell clone with NK-like activity. Two distinct antisense regions of the sequence were used to generate the transfectants alpha NK-TR and alpha Cyclo. Transfectants lost the ability to lyse NK-sensitive targets but did not lose lectin-mediated cytotoxic activity. This effect was not seen with the control vector transfectant cell line. The loss of NK-like activity by the antisense transfectant alpha NK-TR correlated with the specific decrease in endogenous NK-TR mRNA and protein. These results demonstrate the requirement for the NK-TR protein for NK-like killing. Moreover, the results have important implications for examining developmental relationship between T and NK cells and the possible roles for T cells with NK-like activity in vivo.

LGL-1: a potential triggering molecule on murine NK cells

Natural killer (NK) cells mediate non-major histocompatibility complex-restricted lysis of tumor cells, lymphokine-activated killing (LAK), antibody-dependent cellular cytotoxicity (ADCC), and reverse ADCC (RADCC). LGL-1+ cells identify a major subset (50%) of murine NK cells. Here we demonstrate that monoclonal antibodies (mAbs) to LGL-1 consistently induce interleukin-2-cultured, and Corynebacterium parvum (in vivo)-activated NK cells to induce RADCC. LGL-1 triggering of activated NK cells coincides with enhanced LGL-1 expression. Testing of murine mAbs to epitopes of CD2 only appears to augment RADCC induced by mAb NK-1.1 on fresh NK cells. Immunoprecipitation of the LGL-1 antigen reveals a highly disulfide-linked 40-kDa homodimer subunit that is N-glycosylated. Therefore, LGL-1 may be similar to other recently characterized NK-associated antigens such as NK-1.1, Ly-49, and NKR-PI. We conclude that although LGL-1 is expressed on "resting" NK cells, enhanced surface expression following activation is usually required for it to act as a signaling molecule.

Increased proliferation, cytotoxicity, and gene expression after stimulation of human peripheral blood T lymphocytes through a surface ganglioside (GD3)

Previous studies have suggested that gangliosides have an important role in cell signaling and recognition. However, their specific function in these processes has not been clearly defined. A mAb, R24, that reacts specifically with a cell surface ganglioside (GD3) has been demonstrated to stimulate proliferation of T cells derived from human peripheral blood. In this study, we have investigated the mechanisms by which the R24 mAb affects T cell functions. We have observed that the R24 mAb stimulates GD3+ T cell proliferation, cytotoxicity, and surface marker expression of IL-2R alpha-chain, IL-2R beta-chain, HLA-DR, CD11a, and CD11c. Additionally, IFN-gamma activity but not IL-1, IL-2, or IL-4 activity was present in culture supernatants 72 h after R24 stimulation. In some donors, increased IL-6 and TNF-alpha activity also was detected after R24 treatment. Furthermore, R24 treatment resulted in translocation of c-rel, but little or no NF kappa B p50 or p65, from the cytoplasm to the nucleus and an increase of NF kappa B binding complexes containing c-rel and p50. This treatment also caused increased tyrosine phosphorylation of specific protein substrates. R24-stimulated increases in proliferation, cytotoxicity, and cell surface protein expression could be blocked by cyclosporin and staurosporin, indicating that cyclophilin/calcineurin and protein kinase C may be involved in the R24 signaling pathway. Additionally, herbimycin A, a tyrosine kinase inhibitor, blocked the R24-stimulated increase in proliferation but not cytotoxicity at concentrations consistent with specificity for tyrosine kinases. These results suggest that multiple biochemical pathways are involved in the activation of human T cells by R24.

Increased proliferation, cytotoxicity, and gene expression after stimulation of human peripheral blood T lymphocytes through a surface ganglioside (GD3)

Previous studies have suggested that gangliosides have an important role in cell signaling and recognition. However, their specific function in these processes has not been clearly defined. A mAb, R24, that reacts specifically with a cell surface ganglioside (GD3) has been demonstrated to stimulate proliferation of T cells derived from human peripheral blood. In this study, we have investigated the mechanisms by which the R24 mAb affects T cell functions. We have observed that the R24 mAb stimulates GD3+ T cell proliferation, cytotoxicity, and surface marker expression of IL-2R alpha-chain, IL-2R beta-chain, HLA-DR, CD11a, and CD11c. Additionally, IFN-gamma activity but not IL-1, IL-2, or IL-4 activity was present in culture supernatants 72 h after R24 stimulation. In some donors, increased IL-6 and TNF-alpha activity also was detected after R24 treatment. Furthermore, R24 treatment resulted in translocation of c-rel, but little or no NF kappa B p50 or p65, from the cytoplasm to the nucleus and an increase of NF kappa B binding complexes containing c-rel and p50. This treatment also caused increased tyrosine phosphorylation of specific protein substrates. R24-stimulated increases in proliferation, cytotoxicity, and cell surface protein expression could be blocked by cyclosporin and staurosporin, indicating that cyclophilin/calcineurin and protein kinase C may be involved in the R24 signaling pathway. Additionally, herbimycin A, a tyrosine kinase inhibitor, blocked the R24-stimulated increase in proliferation but not cytotoxicity at concentrations consistent with specificity for tyrosine kinases. These results suggest that multiple biochemical pathways are involved in the activation of human T cells by R24.

Activation of peripheral large granular lymphocytes with the serine/threonine phosphatase inhibitor, okadaic acid

The murine polyether fatty acid, okadaic acid, is a potent inhibitor of serine/threonine phosphatases in eukaryotic cells. This compound inhibits both protein phosphatase 1 (PP1) and phosphatase 2A (PP2A). Here we have examined the potential of okadaic acid as an activator of fresh peripheral CD3- large granular lymphocytes (LGL). We demonstrate that overnight exposure of LGL to as little as 1 nM okadaic acid induced an increase in natural killing against the K562 cell line, but does not induce LAK activity. Optimal cytotoxic activation (2-fold) occurred at 0.01-1.0 nM okadaic acid, with a return to baseline levels at 10-20 nM, and inhibition, likely due to toxicity, at 40 nM. In addition, okadaic acid at doses > or = 20 nM induced LGL but not T cells to produce interferon-gamma. Similar to phorbol esters, overnight incubation with okadaic acid causes a dose-dependent reduction in expression of the low-affinity receptor for the Fc portion of IgG (CD16). However, unlike phorbol ester, short-term (5 min) okadaic acid treatment did not block CD16-mediated Ca2+ mobilization in LGL. To address the underlying biochemical mechanisms of okadaic acid activities, the levels of several as-yet-unidentified serine/threonine kinases were assayed after renaturation. Under these conditions, okadaic acid induced similar increases in kinase levels in both T cells and LGL. Taken together, these data suggest an important role for PP1 and PP2A in LGL physiology, and define okadaic acid as a potentially important biological response modifier for the study of LGL and T cell biochemistry, signal transduction, and transcriptional regulation.

Antitumor effects of interleukin-7 and adoptive immunotherapy on human colon carcinoma xenografts

The antitumor properties of recombinant human IL-7 (rhIL-7) on a human tumor was evaluated by engrafting a human colon carcinoma into immunodeficient mice and then treating the mice with rhIL-7 and adoptively transferred human peripheral blood T cells. It was found that rhIL-7 alone had no effect on the survival of the tumor-bearing recipients. However, the combination of rhIL-7 and human T cells significantly promoted the survival of the recipients compared with mice receiving either treatment by itself. When the surviving mice were analyzed 6 mo later for the degree of human cell engraftment, the recipients receiving both rhIL-7 and human T cells had greater numbers of human CD8+ T cells in the spleens. However, the human T cells recovered from the surviving mice showed low lytic activity against the tumor in vitro. Supernatants from human T cells cultured with the tumor and rhIL-7 in vitro were found to inhibit tumor growth and were demonstrated to contain high levels of IFN-gamma. Antibodies to IFN-gamma neutralized the growth inhibition of the tumor both in vitro and in vivo demonstrating that the in vivo mechanism underlying the antitumor effects of this regimen was partly dependent on the production of IFN-gamma by the T cells and not their cytolytic capability. Interestingly, systemic administration of rhIFN-gamma to tumor-bearing mice yielded little antitumor effect suggesting that adoptive immunotherapy with rhIL-7 was superior possibly because of the continuous local release of the cytokines. Therefore, rhIL-7 may be of clinical use as an antineoplastic agent and the human/mouse model is a potentially important preclinical model for in vivo evaluation of the efficacy of this and other immunotherapies.

Mechanisms of cytotoxicity used by human peripheral blood CD4+ and CD8+ T cell subsets. The role of granule exocytosis

The broad lytic properties of high buoyant density CD4+ and CD8+ T cell subsets were examined by activating these populations with anti-CD3 mAb and IL-2 for 1 to 5 days and testing their cytotoxic activity against various target cells. The effects of a variety of metabolic inhibitors and anti-TNF antibodies were examined to distinguish several different mechanisms of cytotoxicity used by CD4+ and CD8+ T cell effectors isolated from human PBL. In particular, activated CD4+ and CD8+ T cells were cytotoxic when redirected by an anti-nitrophenyl (NP)-anti-CD3 mAb heteroconjugate against NP-modified nucleated target cells (TC) and anucleated SRBC and also lysed L929 in a TNF-alpha-dependent manner. CD4+ and CD8+ T cells displayed distinct pathways of antibody-redirected lysis against NP-EL4, yet common mechanisms of SRBC redirected lysis by CD4+ and CD8+ efforts were implied by a similar pattern of sensitivity to cholera toxin, cyclosporin A (CsA), and EGTA. CsA inhibited CD4+ and CD8+ T cell redirected lysis of SRBC, but not EL4, suggesting that T cells redirectedly lyse nucleated and anucleated TC by different mechanisms. Cholera toxin, CsA, or EGTA pretreatment also significantly inhibited their release of alpha-N-benzyloxycarbonyl-L-lysine-thiobenzylester-esterase activity suggesting that degranulation of CD4+ and CD8+ effectors may be a critical step in their redirected lysis of SRBC. Overall, these findings suggested that activated human PBL CD4+ or CD8+ effectors can lyse TC by at least three distinct mechanisms: 1) a CsA-sensitive redirected lysis of SRBC that correlates with exocytosis and presumably occurs via membrane lesions; 2) a CsA-insensitive redirected lysis of NP-modified nucleated TC that does not appear to involve exocytosis and is metabolically distinct in activated CD4+ and CD8+ T cell effectors; and 3) a direct TNF-dependent lysis of TNF-sensitive TC.

Mechanisms of cytotoxicity used by human peripheral blood CD4+ and CD8+ T cell subsets. The role of granule exocytosis

The broad lytic properties of high buoyant density CD4+ and CD8+ T cell subsets were examined by activating these populations with anti-CD3 mAb and IL-2 for 1 to 5 days and testing their cytotoxic activity against various target cells. The effects of a variety of metabolic inhibitors and anti-TNF antibodies were examined to distinguish several different mechanisms of cytotoxicity used by CD4+ and CD8+ T cell effectors isolated from human PBL. In particular, activated CD4+ and CD8+ T cells were cytotoxic when redirected by an anti-nitrophenyl (NP)-anti-CD3 mAb heteroconjugate against NP-modified nucleated target cells (TC) and anucleated SRBC and also lysed L929 in a TNF-alpha-dependent manner. CD4+ and CD8+ T cells displayed distinct pathways of antibody-redirected lysis against NP-EL4, yet common mechanisms of SRBC redirected lysis by CD4+ and CD8+ efforts were implied by a similar pattern of sensitivity to cholera toxin, cyclosporin A (CsA), and EGTA. CsA inhibited CD4+ and CD8+ T cell redirected lysis of SRBC, but not EL4, suggesting that T cells redirectedly lyse nucleated and anucleated TC by different mechanisms. Cholera toxin, CsA, or EGTA pretreatment also significantly inhibited their release of alpha-N-benzyloxycarbonyl-L-lysine-thiobenzylester-esterase activity suggesting that degranulation of CD4+ and CD8+ effectors may be a critical step in their redirected lysis of SRBC. Overall, these findings suggested that activated human PBL CD4+ or CD8+ effectors can lyse TC by at least three distinct mechanisms: 1) a CsA-sensitive redirected lysis of SRBC that correlates with exocytosis and presumably occurs via membrane lesions; 2) a CsA-insensitive redirected lysis of NP-modified nucleated TC that does not appear to involve exocytosis and is metabolically distinct in activated CD4+ and CD8+ T cell effectors; and 3) a direct TNF-dependent lysis of TNF-sensitive TC.

Recombinant human interferon-inducible protein 10 is a chemoattractant for human monocytes and T lymphocytes and promotes T cell adhesion to endothelial cells

The human cytokine interferon-inducible protein 10 (IP-10) is a small glycoprotein secreted by activated T cells, monocytes, endothelial cells, and keratinocytes, and is structurally related to a family of chemotactic cytokines called chemokines. Although this protein is present in sites of delayed-type hypersensitivity reactions and lepromatous leprosy lesions, the biological activity of IP-10 remains unknown. We report here that recombinant human IP-10 stimulated significant in vitro chemotaxis of human peripheral blood monocytes but not neutrophils. Recombinant human IP-10 also stimulated chemotaxis of stimulated, but not unstimulated, human peripheral blood T lymphocytes. Phenotypic analysis of the stimulated T cell population responsive to IP-10 demonstrated that stimulated CD4+ and CD29+ T cells migrated in response to IP-10. This resembles the biological activity of the previously described T cell chemoattractant RANTES. Using an endothelial cell adhesion assay, we demonstrated that stimulated T cells pretreated with optimal doses of IP-10 exhibited a greatly enhanced ability to bind to an interleukin 1-treated endothelial cell monolayer. These results demonstrate that the IP-10 gene encodes for an inflammatory mediator that specifically stimulates the directional migration of T cells and monocytes as well as potentiates T cell adhesion to endothelium.

Engraftment and activity of anti-CD3-activated human peripheral blood lymphocytes transferred into mice with severe combined immune deficiency

Human PBL (huPBL) were activated with anti-CD3 mAb in vitro and then were transferred into mice with severe combined immune deficiency (SCID) to determine the effect of activation on engraftment and to determine if the engrafted human cells could provide antitumor effects in mice. Some mice were also treated with human rIL-2 after huPBL transfer. Mice were analyzed 6 to 8 wk after cell transfer and the number of human cells in the peripheral lymphoid organs was determined. Mice receiving anti-CD3-activated huPBL demonstrated a significant increase in the incidence of human T cell engraftment in the periphery as assessed by flow cytometry. Human cells were also detected in the murine thymus after anti-CD3 stimulation indicating that human T cells can migrate to the murine thymus provided that they are activated before the transfer. The transfer of anti-CD3-activated huPBL also resulted in an xenogeneic graft-vs-host reaction manifested primarily by proliferation of murine splenic hemopoietic cells. When SCID mice received the human colon carcinoma HT29, the concurrent transfer of anti-CD3-activated human cells resulted in a significant increase in survival. However, the human cells displayed low cytolytic activity toward human tumor targets when they were recovered from the lymphoid organs of the SCID recipients. Supernatants from the anti-CD3-activated cells were able to inhibit the growth of HT29 in vitro, partly because of the presence of IFN-gamma, suggesting that the human T cells are producing cytokines in vivo that have antitumor effects. Thus, the use of anti-CD3-activated huPBL in SCID mice may be of value for optimizing human cell engraftment in the human/mouse lymphoid chimeras and may be used to evaluate potential anti-neoplastic therapies that employ human effector cells.

Engraftment and activity of anti-CD3-activated human peripheral blood lymphocytes transferred into mice with severe combined immune deficiency

Human PBL (huPBL) were activated with anti-CD3 mAb in vitro and then were transferred into mice with severe combined immune deficiency (SCID) to determine the effect of activation on engraftment and to determine if the engrafted human cells could provide antitumor effects in mice. Some mice were also treated with human rIL-2 after huPBL transfer. Mice were analyzed 6 to 8 wk after cell transfer and the number of human cells in the peripheral lymphoid organs was determined. Mice receiving anti-CD3-activated huPBL demonstrated a significant increase in the incidence of human T cell engraftment in the periphery as assessed by flow cytometry. Human cells were also detected in the murine thymus after anti-CD3 stimulation indicating that human T cells can migrate to the murine thymus provided that they are activated before the transfer. The transfer of anti-CD3-activated huPBL also resulted in an xenogeneic graft-vs-host reaction manifested primarily by proliferation of murine splenic hemopoietic cells. When SCID mice received the human colon carcinoma HT29, the concurrent transfer of anti-CD3-activated human cells resulted in a significant increase in survival. However, the human cells displayed low cytolytic activity toward human tumor targets when they were recovered from the lymphoid organs of the SCID recipients. Supernatants from the anti-CD3-activated cells were able to inhibit the growth of HT29 in vitro, partly because of the presence of IFN-gamma, suggesting that the human T cells are producing cytokines in vivo that have antitumor effects. Thus, the use of anti-CD3-activated huPBL in SCID mice may be of value for optimizing human cell engraftment in the human/mouse lymphoid chimeras and may be used to evaluate potential anti-neoplastic therapies that employ human effector cells.

A cyclophilin-related protein involved in the function of natural killer cells

Natural killer cells are non-major histocompatibility complex-restricted large granular lymphocytes that can recognize and destroy tumor cells without prior stimulation. A 150-kDa molecule on the surface of human natural killer cells was identified as a component of a putative tumor-recognition complex. We report here the isolation of cDNAs coding for the 150-kDa tumor-recognition molecule from human and mouse cDNA libraries. The amino terminus of the predicted protein contains a large hydrophobic region followed by a domain that is highly homologous to cyclophilin/peptidylprolyl cis-trans isomerase. The remainder of the protein is extremely hydrophilic and contains three homologous positively charged clusters. There are also three regions that contain extensive arginine- and serine-rich repeats. Comparison of the human and mouse predicted amino acid sequences revealed > 80% homology.

Natural killer (NK) cell lytic dysfunction and putative NK cell receptor expression abnormality in members of a family with chromosome 3p-linked von Hippel-Lindau disease

BACKGROUND. Using antibodies to a putative natural killer (NK) cell receptor (pNKR), we recently cloned a novel cDNA and localized this gene to the short arm of human chromosome 3, region 3p21-3p24. Individuals susceptible to or clinically manifesting von Hippel-Lindau disease (VHL) have a genetic defect telomeric to this region on chromosome 3. This defect, resulting in VHL, is manifested by a high incidence of certain tumors.

PURPOSE

Based on the location of this gene, we sought to determine if VHL patients have a defect in gene expression of pNKR.

METHODS

Because of the proximity of the VHL and pNKR genetic regions, the variable expression of VHL tumors, and the ability of NK cells to target tumor cells, we investigated NK cell activity and other aspects of the immunologic status in 40 members (four branches) of a family with a high incidence of VHL tumors.

RESULTS

Individuals affected with VHL and lacking in normal surface expression of pNKR had virtually no NK cell lytic activity. Analysis of genotypes and phenotypes of all subjects revealed that the greatest difference in NK cell lytic activity (P = .0002) was seen when family members exhibited both VHL and pNKR surface expression defects, compared with normal relatives who had neither defect. Furthermore, the lack of NK cell activity strongly correlated (P = .0005) with abnormal pNKR protein surface expression. Of particular interest, individuals who lacked NK cell activity had normal numbers of NK cells. In addition, analysis of leukocyte subsets indicated normal numbers of T and B cells, monocytes, and NK cells in both affected and normal individuals.

CONCLUSIONS

These data indicate that although all affected individuals have the cell population responsible for NK cell activity, many have cells low in expression of pNKR and lack functional NK cell activity. Overall, these results indicate that, in addition to a predisposition to the development of neoplasms, VHL patients have a defect in a specific mechanism of natural immunosurveillance that correlates with a defect in expression of a novel large granular lymphocyte pNKR protein.

Enhanced lymphokine production and lymphokine receptor expression in multiple antibody-stimulated human CD4+ peripheral blood lymphocytes

Treatment of T lymphocytes with antibodies directed against the T cell receptor CD3 complex results in cellular activation that can be augmented by costimulation through other cell surface receptors. The activities of anti-CD3-stimulated human CD4+ PBL were compared to anti-CD3 plus anti-CD2-, anti-CD4-, or anti-CD11a (LFA-1)-stimulated cells. [3H]thymidine incorporation, lymphokine receptor expression, expansion of cell numbers, and lymphokine mRNA and protein were measured. Forty-eight hours after activation, costimulated CD4+ cells demonstrated increased numbers of cells positive for surface IL-2R alpha-chain, IL-2R beta-chain, IFN-gamma receptors, and TNF-alpha receptors. By day 6, costimulated cells exhibited a sevenfold greater expansion in cell numbers compared to cells stimulated with anti-CD3 alone. Anti-CD3 plus anti-CD11a stimulation consistently induced the highest secretion of IL-2 and IFN-gamma, whereas variation in secretion of TNF-alpha and IL-4 between different donors was noted. Analysis of lymphokine receptor mRNA demonstrated increased levels of mRNA for IL-2R alpha-chain and IFN-gamma receptor that preceded the phenotypic changes on the cell surface. In contrast, levels of IL-2R beta-chain and the TNF-alpha receptor mRNA decreased after stimulation. Amounts of IL-2, IL-4, and TNF-alpha, but not IFN-gamma, secreted also correlated with the levels of mRNA measured in the cells. Although costimulation through CD2, CD4, or LFA-1 appeared equally effective for the induction of the lymphokine receptors, these additional stimuli had a different impact on lymphokine secretion. These results indicate that specific control of lymphokine secretion and receptor induction can be another function of the CD2, CD4, and CD11a cell surface receptors. This control is evident at both transcriptional and post-transcriptional levels.

Enhanced lymphokine production and lymphokine receptor expression in multiple antibody-stimulated human CD4+ peripheral blood lymphocytes

Treatment of T lymphocytes with antibodies directed against the T cell receptor CD3 complex results in cellular activation that can be augmented by costimulation through other cell surface receptors. The activities of anti-CD3-stimulated human CD4+ PBL were compared to anti-CD3 plus anti-CD2-, anti-CD4-, or anti-CD11a (LFA-1)-stimulated cells. [3H]thymidine incorporation, lymphokine receptor expression, expansion of cell numbers, and lymphokine mRNA and protein were measured. Forty-eight hours after activation, costimulated CD4+ cells demonstrated increased numbers of cells positive for surface IL-2R alpha-chain, IL-2R beta-chain, IFN-gamma receptors, and TNF-alpha receptors. By day 6, costimulated cells exhibited a sevenfold greater expansion in cell numbers compared to cells stimulated with anti-CD3 alone. Anti-CD3 plus anti-CD11a stimulation consistently induced the highest secretion of IL-2 and IFN-gamma, whereas variation in secretion of TNF-alpha and IL-4 between different donors was noted. Analysis of lymphokine receptor mRNA demonstrated increased levels of mRNA for IL-2R alpha-chain and IFN-gamma receptor that preceded the phenotypic changes on the cell surface. In contrast, levels of IL-2R beta-chain and the TNF-alpha receptor mRNA decreased after stimulation. Amounts of IL-2, IL-4, and TNF-alpha, but not IFN-gamma, secreted also correlated with the levels of mRNA measured in the cells. Although costimulation through CD2, CD4, or LFA-1 appeared equally effective for the induction of the lymphokine receptors, these additional stimuli had a different impact on lymphokine secretion. These results indicate that specific control of lymphokine secretion and receptor induction can be another function of the CD2, CD4, and CD11a cell surface receptors. This control is evident at both transcriptional and post-transcriptional levels.

Direct evidence for release of pore-forming protein during NK cellular lysis

In the present study, we have examined the exocytosis model for cellular lysis. Using monoclonal antibodies reactive with human pore-forming protein (PFP), we examined the localization of PFP at the interaction site of natural killer (NK) cells and the NK tumor targets K562 and Molt-4 as well as during antibody-dependent cellular cytotoxicity. Following the interaction of effector-target cell contact, an increased frequency of PFP was detected on the effector surface, in the micro-environment, and on the target surface of the interaction site. This temporal deposition of PFP was paralleled by loss of target cell integrity and release of chromium. In addition, selective deposition of PFP was seen at the interaction site of the target cell compared to other target cell regions. Collectively, these results are consistent with the exocytosis model and further support the hypothesis that PFP is one of the secreted moieties involved in NK cellular cytotoxicity.

Relationship of large and small CD3- CD56+ lymphocytes mediating NK-associated activities

We have defined a population of CD3-, CD56+ small lymphocytes (SLs) that exhibit the same phenotype and lytic capacity as natural killer (NK) cells. NK cells characteristically express the surface markers CD16 and CD56, mediate non-major histocompatibility complex (MHC)-restricted lysis, and have been equated with CD3- large granular lymphocytes (LGLs). In the present study we extended the observation that CD3-, CD56+ SLs can mediate NK- and antibody-dependent cellular cytotoxicity activity by studying the activation signals and lytic mechanisms that might be utilized by CD3-, CD56+ SLs in comparison to CD3- CD56+ LGLs. Our results show that CD3- SLs, similar to CD3- LGLs, exhibited activated killing in response to interleukin-2 (IL-2). In addition, after IL-2 activation, the CD3- SLs exhibited morphologic changes, including increases in size and granularity, and both morphologically and phenotypically became virtually indistinguishable from CD3- LGLs. Similar to CD3- LGLs, CD3- SLs could be directly activated by IL-2 alone to secrete significant quantities of interferon-gamma (IFN-gamma) and to express IL-2 receptor (IL-2R) p55. Examination of serine esterases and pore-forming protein (PFP) demonstrated that these cells exhibited a cytoplasmic distribution of perforin, which, unlike that of CD3- LGLs, was not associated with dense cytoplasmic azurophilic granules. Serine esterase levels were similar. However, after IL-2 activation PFP was concentrated in dense cytoplasmic granules, similar or identical to the situation in CD3-, CD56+ LGLs. These CD3-, CD56+ subsets appear to represent a continuum of activated cells that might represent various states of maturation of NK cells.

Mechanism of target cell recognition by CD3- LGL. I. Development of a monoclonal antibody to a K562-associated target cell antigen

In an attempt to identify the target recognition molecule(s) involved in the interaction between CD3- large granular lymphocyte (LGL) and a tumor cell target, monoclonal antibodies (mAb) to NK-susceptible K562 tumor cell membrane glycoproteins were developed. After screening by ELISA for reactivity to K562 membrane glycoproteins, two monoclonal antibodies were identified (mAb 35 and mAb 36). One of the monoclonal antibodies (mAb 36) was found to inhibit conjugation between LGL and K562 target cells and also to inhibit lysis of K562 by LGL. Upon further testing, mAb 36 also inhibited the binding between LGL and other NK-susceptible target cells, e.g., Daudi and Molt 4. In contrast, mAb 35, even though binding to K562, did not inhibit the binding of LGL to tumor targets and therefore was used as an isotype control. When mAb 36 was utilized as an affinity matrix, bound proteins specifically inhibited CD3- LGL-K562 conjugation. Experiments involving tunicamycin treatment of tumor target cells demonstrated that mAb 36 recognized a carbohydrate moiety rather than the protein core. Therefore, these data suggested that the target cell recognition molecule which is recognized by mAb 36 appears to be a membrane carbohydrate-associated molecule.

A role for protein tyrosine kinase activity in natural cytotoxicity as well as antibody-dependent cellular cytotoxicity. Effects of herbimycin A

NK cells, CD3- large granular lymphocytes, have diverse means by which they lyse targets, including antibody-dependent cellular cytotoxicity. The low affinity receptor for the Fc portion of Ig (Fc gamma RIIIA), like the TCR, is a multimeric receptor complex coupled to a protein tyrosine kinase. In the present study, we observed that inhibition of tyrosine kinase activity by herbimycin A interferes with receptor-mediated phosphorylation of a variety of substrates and mobilization of intracellular calcium. Fc gamma RIIIA induced IL-2R alpha-chain expression was also extremely sensitive to herbimycin A as was antibody-dependent cellular cytotoxicity, in fact more so than receptor-mediated phosphorylation and calcium mobilization. In contrast to Fc gamma RIIIA, the surface molecules and biochemical mechanisms involved in NK cytotoxicity and lymphokine-activated killing are not well characterized. Interestingly, however, herbimycin A also blocks these modes of cytolysis, implicating a role for tyrosine kinase function in these processes. Whether FcR-mediated signaling and receptor-mediated signaling involved in NK activity share specific biochemical intermediates is not known, but the involvement of tyrosine kinase function in the latter means of cytotoxicity may provide novel avenues for understanding the biochemical basis of this perplexing cellular function.

A role for protein tyrosine kinase activity in natural cytotoxicity as well as antibody-dependent cellular cytotoxicity. Effects of herbimycin A

NK cells, CD3- large granular lymphocytes, have diverse means by which they lyse targets, including antibody-dependent cellular cytotoxicity. The low affinity receptor for the Fc portion of Ig (Fc gamma RIIIA), like the TCR, is a multimeric receptor complex coupled to a protein tyrosine kinase. In the present study, we observed that inhibition of tyrosine kinase activity by herbimycin A interferes with receptor-mediated phosphorylation of a variety of substrates and mobilization of intracellular calcium. Fc gamma RIIIA induced IL-2R alpha-chain expression was also extremely sensitive to herbimycin A as was antibody-dependent cellular cytotoxicity, in fact more so than receptor-mediated phosphorylation and calcium mobilization. In contrast to Fc gamma RIIIA, the surface molecules and biochemical mechanisms involved in NK cytotoxicity and lymphokine-activated killing are not well characterized. Interestingly, however, herbimycin A also blocks these modes of cytolysis, implicating a role for tyrosine kinase function in these processes. Whether FcR-mediated signaling and receptor-mediated signaling involved in NK activity share specific biochemical intermediates is not known, but the involvement of tyrosine kinase function in the latter means of cytotoxicity may provide novel avenues for understanding the biochemical basis of this perplexing cellular function.

Multiple cytolytic mechanisms displayed by activated human peripheral blood T cell subsets

It has been proposed that CTL-mediated cytotoxicity may involve multiple lytic mechanisms. We have examined both the antibody-redirected cytolytic potential and the direct cytotoxicity of purified human peripheral blood high buoyant density CD4+ and CD8+ T cells activated with IL-2 and anti-CD3 mAb. TNF-sensitive and TNF-resistant targets and various metabolic inhibitors were used to compare the antibody-redirected cytotoxicity of T cell subsets and discern the role of potential lytic mediators. In a 4-h assay against several different nitrophenyl-modified targets, the heteroconjugated antibody (anti-CD3-anti-nitrophenyl) redirected cytolytic potential of 72-h activated CD4+ T cells was inhibited by the continuous presence of actinomycin D, cycloheximide, and EGTA, but not mitomycin C, cyclosporin A, or cholera toxin (CT). Conversely, only CT and EGTA inhibited the antibody-redirected cytolytic potential of activated CD8+ T cells. Despite both CD4+ and CD8+ T cell subsets expressing granzymes, pore-forming protein, TNF-beta, and TNF-alpha, these T cell subsets displayed distinct pathways of antibody-redirected lysis against TNF-sensitive and TNF-resistant targets, even in the presence of anti-TNF antibodies. In addition, these same effector T cell subsets were also directly cytotoxic (in the absence of heteroconjugated antibody) against TNF-sensitive targets in an 18-h assay. Indeed, this direct cytotoxicity was completely abrogated by anti-TNF-alpha antibody and was sensitive to the metabolic inhibitors (cyclosporin A, CT, cycloheximide, and actinomycin D), all of which blocked CD4+/CD8+ T cell TNF-alpha production. Therefore, both CD4+ and CD8+ T cells were demonstrated to utilize antibody and lymphokine-mediated lytic mechanisms. CD4+ and CD8+ effector subsets were demonstrated to lyse the same TNF-sensitive target by these two different mechanisms. Although it cannot be excluded that the redirected lytic mechanisms of both CD4+ and CD8+ effectors share common elements, it is likely that other important events in this cytolytic process are fundamentally distinct between these subsets of T cells.

Multiple cytolytic mechanisms displayed by activated human peripheral blood T cell subsets

It has been proposed that CTL-mediated cytotoxicity may involve multiple lytic mechanisms. We have examined both the antibody-redirected cytolytic potential and the direct cytotoxicity of purified human peripheral blood high buoyant density CD4+ and CD8+ T cells activated with IL-2 and anti-CD3 mAb. TNF-sensitive and TNF-resistant targets and various metabolic inhibitors were used to compare the antibody-redirected cytotoxicity of T cell subsets and discern the role of potential lytic mediators. In a 4-h assay against several different nitrophenyl-modified targets, the heteroconjugated antibody (anti-CD3-anti-nitrophenyl) redirected cytolytic potential of 72-h activated CD4+ T cells was inhibited by the continuous presence of actinomycin D, cycloheximide, and EGTA, but not mitomycin C, cyclosporin A, or cholera toxin (CT). Conversely, only CT and EGTA inhibited the antibody-redirected cytolytic potential of activated CD8+ T cells. Despite both CD4+ and CD8+ T cell subsets expressing granzymes, pore-forming protein, TNF-beta, and TNF-alpha, these T cell subsets displayed distinct pathways of antibody-redirected lysis against TNF-sensitive and TNF-resistant targets, even in the presence of anti-TNF antibodies. In addition, these same effector T cell subsets were also directly cytotoxic (in the absence of heteroconjugated antibody) against TNF-sensitive targets in an 18-h assay. Indeed, this direct cytotoxicity was completely abrogated by anti-TNF-alpha antibody and was sensitive to the metabolic inhibitors (cyclosporin A, CT, cycloheximide, and actinomycin D), all of which blocked CD4+/CD8+ T cell TNF-alpha production. Therefore, both CD4+ and CD8+ T cells were demonstrated to utilize antibody and lymphokine-mediated lytic mechanisms. CD4+ and CD8+ effector subsets were demonstrated to lyse the same TNF-sensitive target by these two different mechanisms. Although it cannot be excluded that the redirected lytic mechanisms of both CD4+ and CD8+ effectors share common elements, it is likely that other important events in this cytolytic process are fundamentally distinct between these subsets of T cells.