Specific release of proteoglycans from human natural killer cells during target lysis

Investigation of serum endocan and serglycin levels in obstructive sleep apnea

BACKGROUND

Apnea-related hypoxia, hypercapnia, and blood pressure fluctuations cause production of various proinflammatory cytokines and trigger a vicious cycle that results in vascular endothelial damage and systemic inflammation in obstructive sleep apnea (OSA). Endothelial function is frequently impaired in OSA even in the absence of significant cardiac or vascular disorders.

AIMS

This study aimed to investigate the serum endocan and serglycin levels in OSA patients.

METHODS

This prospective study included 78 consecutive patients who admitted to the sleep laboratory of a tertiary referral center with the complaints of daytime sleepiness, witnessed sleep apnea, and/or snoring and who underwent all-night polysomnography (PSG). After PSG, the patients were divided into four groups in relation with their apnea-hypopnea indexes. The groups were compared for endocan and serglycin levels and their correlations with OSA severity. The correlations with demographic data and PSG findings were also investigated.

RESULTS

The OSA and the control groups had significantly different endocan and serglycin levels ([Formula: see text], for both). On univariate logistic regression analysis, it was found that serglycin and endocan levels and BMI were predictors of OSA. Multiple logistic regression analysis showed that endocan and serglycin levels were independent predictors for OSA ([Formula: see text] and [Formula: see text], respectively).

CONCLUSIONS

We have demonstrated that elevated endocan and serglycin levels are predictors for OSA. Furthermore, we have showed for the first time in literature that serglycin is correlated with OSA and is an independent predictor for OSA.

The TLR-2/TLR-6 agonist macrophage-activating lipopeptide-2 augments human NK cell cytotoxicity when PGE2 production by monocytes is inhibited by a COX-2 blocker

Macrophage-activating lipopeptide-2 (MALP-2) is a potent inducer of proinflammatory cytokine secretion by macrophages, monocytes, and dendritic cells. MALP-2 was reported to be involved in natural killer (NK) cell activation and ensuing tumor rejection. However, the mechanism of MALP-2-mediated NK cell activation remained unclear. Therefore, we studied the effects of MALP-2 on cultured human NK cells. We found that MALP-2 had no direct effect on NK cells. Instead, MALP-2 acted on monocytes and triggered the release of different molecules such as interleukin (IL)-1β, IL-6, IL-10, IL-12, IL-15, interferon gamma-induced protein (IP-10), and prostaglandin (PG)-E2. Our data show that monocyte-derived IP-10 could significantly induce NK cell cytotoxicity as long as the immunosuppression by PGE2 is specifically inhibited by cyclooxygenase (COX)-2 blockade. In summary, our results show that MALP-2-mediated stimulation of monocytes results in the production of several mediators which, depending on the prevailing conditions, affect the activity of NK cells in various ways. Hence, MALP-2 administration with concurrent blocking of COX-2 can be considered as a promising approach in MALP-2-based adjuvant tumor therapies.

Role of gamma-secretase in human umbilical-cord derived mesenchymal stem cell mediated suppression of NK cell cytotoxicity

Background

Mesenchymal stem cells (MSCs) are increasingly considered to be used as biological immunosuppressants in hematopoietic stem cell transplantation (HSCT). In the early reconstitution phase following HSCT, natural killer (NK) cells represent the major lymphocyte population in peripheral blood and display graft-vs-leukemia (GvL) effects. The functional interactions between NK cells and MSCs have the potential to influence the leukemia relapse rate after HSCT. Until date, MSC-NK cell interaction studies are largely focussed on bone marrow derived (BM)-MSCs. Umbilical cord derived (UC)-MSCs might be an alternative source of therapeutic MSCs. Thus, we studied the interaction of UC-MSCs with unstimulated allogeneic NK cells.

Results

UC-MSCs could potently suppress NK cell cytotoxicity in overnight cultures via soluble factors. The main soluble immunosuppressant was identified as prostaglandin (PG)-E2. Maximal PGE2 release involved IL-1β priming of MSCs after close contact between the NK cells and UC-MSCs. Interestingly, blocking gamma-secretase activation alleviated the immunosuppression by controlling PGE2 production. IL-1 receptor activation and subsequent downstream signalling events were found to require gamma-secretase activity.

Conclusion

Although the role of PGE2 in NK cell-MSC has been reported, the requirement of cell-cell contact for PGE2 induced immunosuppression remained unexplained. Our findings shed light on this puzzling observation and identify new players in the NK cell-MSC crosstalk.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-014-0063-9) contains supplementary material, which is available to authorized users.

Immunostimulating effect of a well-known Thai folkloric remedy in breast cancer patients

The study aimed to evaluate immune-stimulating effects of a well-known Thai folkloric remedy when used for adjuvant therapy with conventional chemotherapeutics for treatment of breast cancer. Immunostimulating influence of the remedy (215 mg/kg body weight per day) on NK cell activity and TNF-α release from the monocytes/macrophages were investigated in a total of 15 healthy women and 13 female patients with breast cancer (Group 1). The effect of breast tumor surgery on NK cell activity was further investigated in 18 female patients with breast cancer (Group 2). NK cell cytotoxic activity was determined by chromium release cytotoxic assay using K562, an erythroleukemic cell line. TNF-α release from monocytes/macrophages separated from blood samples was determined through a biological assay using actinomycin D-treated L929 mouse fibroblast cells in the presence and absence of LPS. Baseline NK cell activity of the monocytes/macrophages separated from Group 2 patients expressed as %cytotoxicity was significantly lower than in the healthy subjects at E:T ratios of 100:1 and 25:1. In healthy subjects, there was no change in NK cell cytotoxic activity (%cytotoxicity or LU) following 1 and 2 weeks of treatment with the remedy compared with the baseline at various E:T ratios but the binding activity (%binding) was significantly increased after 2 weeks of treatment. The addition of one or two conventional chemotherapeutic regimens did not significantly reduce the NK cytotoxic activity but did affect release of TNF-α in both unstimulated and LPS-stimulated samples. Surgery produced a significant suppressive effect on NK cell activity. The use of the remedy as an adjunct therapy may improve therapeutic efficacy and safety profiles of conventional chemotherapeutic regimens through stimulation of the immune system in cancer patients.

Serglycin: a structural and functional chameleon with wide impact on immune cells

Among the different proteoglycans expressed by mammals, serglycin is in most immune cells the dominating species. A unique property of serglycin is its ability to adopt highly divergent structures, because of glycosylation with variable types of glycosaminoglycans when expressed by different cell types. Recent studies of serglycin-deficient animals have revealed crucial functions for serglycin in a diverse array of immunological processes. However, its exact function varies to a large extent depending on the cellular context of serglycin expression. Based on these findings, serglycin is emerging as a structural and functional chameleon, with radically different properties depending on its exact cellular and immunological context.

Granzymes, cytotoxic granules and cell death: the early work of Dr. Jurg Tschopp

Within the powerful legacy left by Jurg Tschopp, we should not forget his early work that helped to elucidate the molecular pathways responsible for the clearance of virus-infected and transformed cells by cytotoxic T lymphocytes (CTL) and natural killer (NK) cells. Jurg's skilful biochemical approach formed a firm platform upon which the work of so many other biochemists, cell biologists and immunologists would come to rely. Jurg coined the shorthand term 'granzyme' to denote the individual members of a family of serine proteases sequestered in and secreted from the cytotoxic granules of CTL/NK cells. He was also one of the first to describe the lytic properties of purified perforin and to postulate the synergy of perforin and granzymes, which we now know to underpin target cell apoptosis. Jurg was a major protagonist in the debate that raged throughout the 1980's and early 1990's on the physiological relevance of the 'granule exocytosis' pathway. Ultimately, resolving this issue led Jurg and his colleagues to even greater and impactful discoveries in the broader field of apoptosis research. Jurg Tschopp ranks with other pioneers, particularly Gideon Berke, Chris Bleackley, Pierre Golstein, Pierre Henkart and Eckhard Podack for making seminal discoveries on our understanding of how the immune system eliminates dangerous cells.

Proposed Recommended Nutrient Densities for Moderately Malnourished Children

Recommended Nutrient Intakes (RNIs) are set for healthy individuals living in clean environments. There are no generally accepted RNIs for those with moderate malnutrition, wasting, and stunting, who live in poor environments. Two sets of recommendations are made for the dietary intake of 30 essential nutrients in children with moderate malnutrition who require accelerated growth to regain normality: first, for those moderately malnourished children who will receive specially formulated foods and diets; and second, for those who are to take mixtures of locally available foods over a longer term to treat or prevent moderate stunting and wasting. Because of the change in definition of severe malnutrition, much of the older literature is pertinent to the moderately wasted or stunted child. A factorial approach has been used in deriving the recommendations for both functional, protective nutrients (type I) and growth nutrients (type II).

Serglycin proteoglycan: regulating the storage and activities of hematopoietic proteases

Serglycin (SG), like all other proteoglycans, consists of a protein "core" to which sulfated and thereby negatively charged polysaccharide chains of glycosaminoglycan type are attached. The recent generation of mice lacking a functional SG gene has revealed a number of biological functions of SG. In particular, it has been shown that SG has a key role in promoting the storage and in regulating the activities of a number of proteases expressed in hematopoietic cell types, most notably various mast cell proteases. In this review, we summarize the recent development in our understanding of the biological function of SG, in particular by focusing on the novel insight provided through analysis of the SG-deficient mouse strain.

Delayed contraction of the CD8+ T cell response toward lymphocytic choriomeningitis virus infection in mice lacking serglycin

We previously reported that the lack of serglycin proteoglycan affects secretory granule morphology and granzyme B (GrB) storage in in vitro generated CTLs. In this study, the role of serglycin during viral infection was studied by infecting wild-type (wt) mice and serglycin-deficient (SG(-/-)) mice with lymphocytic choriomeningitis virus (LCMV). Wt and SG(-/-) mice cleared 10(3) PFU of highly invasive LCMV with the same kinetics, and the CD8(+) T lymphocytes from wt and SG(-/-) animals did not differ in GrB, perforin, IFN-gamma, or TNF-alpha content. However, when a less invasive LCMV strain was used, SG(-/-) GrB(+) CD8(+) T cells contained approximately 30% less GrB than wt GrB(+) CD8(+) T cells. Interestingly, the contraction of the antiviral CD8(+) T cell response to highly invasive LCMV was markedly delayed in SG(-/-) mice, and a delayed contraction of the virus-specific CD8(+) T cell response was also seen after infection with vesicular stomatitis virus. BrdU labeling of cells in vivo revealed that the delayed contraction was associated with sustained proliferation of Ag-specific CD8(+) T cells in SG(-/-) mice. Moreover, wt LCMV-specific CD8(+) T cells from TCR318 transgenic mice expanded much more extensively in virus-infected SG(-/-) mice than in matched wt mice, indicating that the delayed contraction represents a T cell extrinsic phenomenon. In summary, the present report points to a novel, previously unrecognized role for serglycin proteoglycan in regulating the kinetics of antiviral CD8(+) T cell responses.

Serglycin proteoglycan deletion induces defects in platelet aggregation and thrombus formation in mice

Serglycin (SG), the hematopoietic cell secretory granule proteoglycan, is crucial for storage of specific secretory proteins in mast cells, neutrophils, and cytotoxic T lymphocytes. We addressed the role of SG in platelets using SG-/- mice. Wild-type (WT) but not SG-/- platelets contained chondroitin sulfate proteoglycans. Electron microscopy revealed normal alpha-granule structure in SG-/- platelets. However, SG-/- platelets and megakaryocytes contained unusual scroll-like membranous inclusions, and SG-/- megakaryocytes showed extensive emperipolesis of neutrophils. SG-/- platelets had reduced ability to aggregate in response to low concentrations of collagen or PAR4 thrombin receptor agonist AYPGKF, and reduced fibrinogen binding after AYPGKF, but aggregated normally to ADP. 3H-serotonin and ATP secretion were greatly reduced in SG-/- platelets. The alpha-granule proteins platelet factor 4, beta-thromboglobulin, and platelet-derived growth factor were profoundly reduced in SG-/- platelets. Exposure of P-selectin and alphaIIb after thrombin treatment was similar in WT and SG-/- platelets. SG-/- mice exhibited reduced carotid artery thrombus formation after exposure to FeCl3. This study demonstrates that SG is crucial for platelet function and thrombus formation. We propose that SG-/- platelet function deficiencies are related to inadequate packaging and secretion of selected alpha-granule proteins and reduced secretion of dense granule contents critical for platelet activation.

Secretory granule proteoglycans of mast cells and natural killer cells

Proteoglycan research on cells that participate in immune responses has progressed from the early novel finding that heparin proteoglycans are present in the secretory granules of the connective tissue mast cell to the more recent findings that mucosal mast cells and natural killer (NK) cells possess chondroitin sulphate proteoglycans in their granules. Characterization studies of these intracellular proteoglycans have revealed that they all possess peptide cores which are very resistant to proteolytic degradation. Their glycosaminoglycans, however, differ in such parameters as the type of hexosamine, location of sulphation degree of sulphation, or extent of epimerization of the uronic acid. Amino acid compositional analyses of heparin proteoglycans from rat connective tissue mast cells and chondroitin sulphate E proteoglycans from mouse mucosal mast cells indicate that their peptide cores are homologous to, but possibly distinct from one another. It is not yet known if these differences reflect a species variation, are due to different post-translational proteolytic processing, or are the result of expression of distinct genes coding for different peptide cores. The proteoglycans of mast cells and natural killer cells are packaged in the granules with cationic proteins. In mast cells these proteins have been shown to be serine proteases, and when bound to the acidic proteoglycans their enzymic activity is inhibited. Since the type of glycosaminoglycan linked to the proteoglycan has been found to be a characteristic of that cell, the structure of the cell-associated proteoglycan has become one of the markers used to distinguish cells phenotypically. By following the expression of different proteoglycans during differentiation, the relationship of the two subclasses of mast cells has been determined.

Characterization of cord blood natural killer and lymphokine activated killer lymphocytes following ex vivo cellular engineering

Cord blood (CB) natural killer (NK) and lymphokine-activated killer (LAK) cytotoxic cells are poorly characterized but might be used to treat minimal residual and/or recurrent malignant disease. Currently, there is no mechanism to use CB for adoptive cancer cellular immunotherapy after CB transplantation (CBT). Recognizing this as a deficiency, we hypothesized that CB aliquots could be engineered ex vivo for potential donor lymphocyte infusion after CBT. Cryopreserved CB aliquots were thawed, depleted of monocytes, and cultured in serum-free medium alone or serum-free medium with anti-CD3 and interleukins 2, 7, and 12 combined with antibody/cytokines for 48 hours. Immunophenotyping, cytotoxicity, and proliferation were evaluated. A significant expansion of CD3+ was seen, in addition to increases in lymphocyte subsets of CD8+, CD8+/CD25+, and CD3+/45RO+ versus medium alone. A significant enhancement of CD3 proliferation (P<.001), NK cytotoxicity, NK subset expansion, LAK cytotoxicity, and T-helper 1 subset expansion was also demonstrated. Significant enrichment was seen in NK CD16+/CD56+bright, CD16+/CD56+dim, CD56+bright and CD56+dim/KIR3DL1+, CD56+bright and CD56+dim/KIR2DL1+, CD56+bright and CD56+dim/KIR2DL2+ and CD94+/NKG2a+ subsets. These increases in CB NK subsets were in part secondary to augmentation of cell survival. Further, survival of NOD-SCID mice xenografted with human K562 cells and treated with CB cells expanded with antibody/cytokines was significantly higher than that in animals that received no treatment (phosphate buffered saline) and those that were treated with CB ex vivo expanded in medium alone (P<.005, respectively). These data suggest that cryopreserved CB cells could be ex vivo engineered for potential use as adoptive cancer cellular immunotherapy for donor lymphocyte infusion after CBT.

Serglycin-deficient cytotoxic T lymphocytes display defective secretory granule maturation and granzyme B storage

Cytotoxic T lymphocytes eliminate infected and tumor cells mainly by perforin/granzyme-induced apoptosis. Earlier studies suggested that serglycin-proteoglycans form macromolecular complexes with granzymes and perforin in the cytotoxic granule. Serglycin-proteoglycans may also be involved in the delivery of the cytolytic machinery into target cells. We have developed a serglycin-deficient mouse strain, and here we studied the importance of serglycin-proteoglycans for various aspects of cytotoxic T lymphocyte function. 35SO4(2-) radiolabeling of serglycin-deficient cells demonstrated a dramatic reduction of incorporated label as compared with wild type cells, indicating that serglycin is by far the dominating proteoglycan species produced by the cytotoxic T lymphocyte. Moreover, lack of serglycin resulted in impaired ability of cytotoxic T lymphocytes to produce secretory granule of high electron density, although granule of lower electron density were produced both in wild type and serglycin-deficient cells. The serglycin deficiency did not affect the mRNA expression for granzyme A, granzyme B, or perforin. However, the storage of granzyme B, but not granzyme A, Fas ligand, or perforin, was severely defective in serglycin-deficient cells. Serglycin-deficient cells did not display defects in late cytotoxicity toward target cell lines. Taken together, these results point to a key role for serglycin in the storage of granzyme B and for secretory granule maturation but argue against a major role for serglycin in the apoptosis mediated by cytotoxic T lymphocytes.

Mutual interference of HIV and natural killer cell-mediated immune response

Natural killer (NK) cells represent important early effector cells in innate immune defense as they exert their functions without prior sensitization. They participate in regulation of innate and adaptive immune responses and hematopoiesis by producing various cytokines and chemokines. In addition, NK cells lyse virally infected and malignant cells raising them to multifunctional members of the first line of defense. Unlike other lymphocytes they lack specific antigen receptors. They rather bind cells using ubiquitous molecules and communicate via a pattern of receptors specific for MHC-I molecules with their counterparts. In general, successful binding of the receptors delivers an inhibitory signal to NK cells thus sparing the target cell from lysis. In contrast, down-regulated or altered MHC-I expression as frequently observed during virus infection or on malignant cells prevents ligation of inhibitory receptors and MHC-I paralyzing inhibition and thus inducing lysis of the target cell. In human immunodeficiency virus (HIV) infection NK cells are of central importance since they can combat viral infection itself and opportunistic pathogens like fungi and protozoa that usually spread during the course of HIV infection. However, various studies have reported alterations in HIV patients affecting NK cell numbers and functions that might negatively influence course and severity of the disease. This review will focus on the mutual interference of NK cells and the HI virus.

Cytotoxic granule-mediated apoptosis: unraveling the complex mechanism

The molecular details of cytotoxic granule-mediated apoptosis have been gleaned from the study of the effects of isolated granzymes and perforin on target cells. Recent evidence indicates that the physiological apoptosis-inducing form is a multi-component macro-complex consisting of cationic granule proteins non-covalently linked to the chondroitin-sulfate proteoglycan, serglycin.

A role for chondroitin sulphate B in the activity of interleukin 12 in stimulating gamma-interferon secretion

We show, using a murine NK cell line which responds quantitatively to rmIL-12, that treatment with ChABCase, but not other GAGases, results in substantial reductions in the secretion of gamma-IFN. Likewise, treatment of the cells with a beta-D-xyloside inhibitor of proteoglycan biosynthesis inhibits this cytokine response. In both treatments, the addition of soluble, exogenous GAGs does not relieve the inhibition of gamma-IFN secretion. We also demonstrate by ELISA that rmIL-12 binds to CS B. Overall, our studies on this in vitro cellular model of the initiation of Th1 immune responses indicate a major role for cell-surface, iduronate-rich, CS proteoglycan in the biological activity of IL-12.

Dendritic cells: making progress with tumour regression?

Due to their potent ability to activate the immune system, dendritic cells (DC) are showing promise as potential adjuvants for tumour immunotherapy of cancer patients. However, little is known about the effect tumour cells can have on DC function. Indeed, the discovery of different DC subsets with different immunological functions indicates that the relationship between tumour cells and tumour-infiltrating DC subtypes is likely to be complex. There remains a lot to be understood about the effects of tumours on DC before we can expect to benefit from DC-based tumour immunotherapy of cancer patients. Here we review the recent advances being made in understanding DC phenotype and function in relation to interactions with different types of tumours.

CD56bright cells differ in their KIR repertoire and cytotoxic features from CD56dim NK cells

In this study we present new differential characteristics of NK cells expressing CD56 surface antigen in low (CD56dim) or high (CD56bright) density. In contrast to CD56bright NK cells CD56dim cells express killer cell immunoglobulin (Ig)-like receptors (KIR) such as CD158a, CD158b, and NKB1. However, c-type lectin-like receptors (KLR) CD94/NKG2 and CD161 are present on both subsets. The ability to form conjugates with susceptible targets is approximately twice as strongly pronounced in CD56dim vs. CD56bright NK cells. Last but not least, granules of CD56dim cells contain about tenfold more perforin and granzyme A enabling potentially more effective cytolysis compared to CD56bright NK cells. On the other hand, CD56bright NK cells are superior in producing the proinflammatory cytokines IFN-gamma (28.5% vs. 20.8%, p<0.05) and TNF-alpha (28% vs. 15.8%, p<0.001). The different NK cell populations retained their specific phenotype in vitro during culture in the presence of IL-2 contradicting that they simply display different stages of maturity. Taken together our data support the view that CD56bright cells are specialized NK cells that regulate immunological response mechanisms rather by cytokine supply than by their cytotoxic potential. The poor cytolytic capacity of CD56bright NK cells can be explained by weak ability in forming conjugates with target cells and low contents of perforin and granzyme A in their granules.

CD56bright cells differ in their KIR repertoire and cytotoxic features from CD56dim NK cells

In this study we present new differential characteristics of NK cells expressing CD56 surface antigen in low (CD56dim) or high (CD56bright) density. In contrast to CD56bright NK cells CD56dim cells express killer cell immunoglobulin (Ig)-like receptors (KIR) such as CD158a, CD158b, and NKB1. However, c-type lectin-like receptors (KLR) CD94/NKG2 and CD161 are present on both subsets. The ability to form conjugates with susceptible targets is approximately twice as strongly pronounced in CD56dim vs. CD56bright NK cells. Last but not least, granules of CD56dim cells contain about tenfold more perforin and granzyme A enabling potentially more effective cytolysis compared to CD56bright NK cells. On the other hand, CD56bright NK cells are superior in producing the proinflammatory cytokines IFN-gamma (28.5% vs. 20.8%, p<0.05) and TNF-alpha (28% vs. 15.8%, p<0.001). The different NK cell populations retained their specific phenotype in vitro during culture in the presence of IL-2 contradicting that they simply display different stages of maturity. Taken together our data support the view that CD56bright cells are specialized NK cells that regulate immunological response mechanisms rather by cytokine supply than by their cytotoxic potential. The poor cytolytic capacity of CD56bright NK cells can be explained by weak ability in forming conjugates with target cells and low contents of perforin and granzyme A in their granules.

Systemic lupus erythematosus and rheumatoid arthritis patients differ from healthy controls in their cytokine pattern after stress exposure

OBJECTIVE

To study whether patients with rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE) differ from healthy individuals in their immune responses to acute psychological stress.

METHODS

The phenotype and function of peripheral blood lymphocytes were analysed before and after stress exposure in patients and healthy subjects.

RESULTS

Natural killer (NK) cell numbers increased transiently in all groups under stress. NK activity, however, increased in healthy controls only. We observed a stress-induced increase in interleukin (IL)-4-producing (IL-4(+)) cells in SLE patients only, whereas interferon (IFN) gamma(+) cell numbers increased due to stress in all three groups. An analysis of supernatants from phytohaemagglutinin (PHA) cultures revealed increased IFN gamma and IL-10 levels in healthy subjects but not in SLE or RA patients after stress exposure.

CONCLUSIONS

These data demonstrate that RA and SLE patients differ in their immune response to stress from healthy controls. Changes in cytokine patterns might be responsible for stress-induced exacerbation of disease activity in RA and SLE patients.

Extracellular granzyme A, complexed to proteoglycans, is protected against inactivation by protease inhibitors

Granzyme A (GrA) and B (GrB) together with perforin are the main constituents of cytotoxic granules of cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. The cytotoxic proteins are released to deliver a lethal hit during contact between the CTL or NK cell and target cell. With the use of an enzyme-linked immunosorbent assay for antigenic levels, we showed in a recent study that plasma of patients with activated CTLs and NK cells contain elevated levels of extracellular GrA. In this study, we determined the form and proteolytic capacity of this extracellular GrA detected in plasma. With the use of various assays, we show that part of the extracellular GrA circulates in the mature conformation and is bound to proteoglycans that protect it against inactivation by protease inhibitors, such as antithrombin III and -2-macroglobulin, whereas another part of GrA circulates as a complex with antithrombin III. Finally, with the use of a novel assay for active GrA, we demonstrate that some plasma samples with high levels of extracellular GrA contain active GrA. These results suggest that various forms of extracellular GrA occur in vivo and that the regulation of GrA activity may be modified by proteoglycans. These data support the notion that granzymes may exert extracellular functions distant from the site of CTL or NK cell interaction with their target cells.

Effects of fentanyl on cellular immune functions in man

In order to analyze the effects of the opioid agonist fentanyl on cells of the innate immune system, seven healthy individuals were treated intravenously with the opioid fentanyl and five subjects received a placebo. Respiratory burst of polymorphonuclear cells (PMNC) and phenotypes of peripheral blood lymphocytes (PBL) were analyzed from blood samples drawn before, 15 and 30 min after fentanyl or placebo application. In addition, in vitro effects of fentanyl on natural killer (NK) activity was assessed. Fentanyl administration affected neither superoxide production of PMNC nor circulating numbers of B-and T-lymphocytes. In contrast, NK cell (CD16+/CD56+) numbers significantly increased in response to fentanyl. However, no direct influence of fentanyl on NK cell function in vitro could be detected. These results suggest a transient effect of fentanyl on NK cell circulation which seemed to be centrally mediated rather than a direct effect of this opioid on NK cells.

Transcriptional and posttranscriptional regulation of proteoglycan gene expression

Proteoglycans are among the most complex and sophisticated molecules of mammalian systems in terms of their protein and carbohydrate moieties. These macromolecules are in a continuous interplay with each other and the cell surface signal-transducing pathways, some of which are beginning to be elucidated. Because of their domain structure, catalytic potential, and diversity, these molecules appear to be designed for integrating numerous signaling events. For example, some proteoglycans interact with hyaluronan and lectins, thereby linking cell surfaces and distant matrix molecules. Some interact with collagen during the complex process of fibrillogenesis and regulate this biological process fundamental to animal life. Others interact with growth factors and serve as depot available during growth or tissue remodeling. In this review, we center on the most recent developments of proteoglycan biology, focusing primarily on genomic organization and transcriptional and posttranscriptional control. We discuss only those proteoglycans whose gene and promoter elements have been characterized and proved to be functional. When possible, we correlate the effects of growth factors and cytokines on proteoglycan gene expression with the topology of cis-acting elements in their genomic control regions. The analysis leads to a comprehensive critical appraisal of the principles that underlie the regulation of proteoglycan gene expression and to the delineation of common regulatory mechanisms.

Anti-viral strategies of cytotoxic T lymphocytes are manifested through a variety of granule-bound pathways of apoptosis induction

Cytotoxic T cells and natural killer cells together constitute a major defence against virus infection, through their ability to induce apoptotic death in infected cells. These cytolytic lymphocytes kill their targets through two principal mechanisms, and one of these, granule exocytosis, is essential for an effective in vivo immune response against many viruses. In recent years, the authors and other investigators have identified several distinct mechanisms that can induce death in a targeted cell. In the present article, it is postulated that the reason for this redundancy of lethal mechanisms is to deal with the array of anti-apoptotic molecules elaborated by viruses to extend the life of infected cells. The fate of such a cell therefore reflects the balance of pro-apoptotic (immune) and anti-apoptotic (viral) strategies that have developed over eons of evolutionary time.

Increased natural killer cell cytotoxicity in Alzheimer's disease may involve protein kinase C dysregulation

Increased cytokine-mediated cytotoxic natural killer (NK) cell activity has recently been demonstrated in patients with senile dementia of the Alzheimer's type (SDAT). In the present study, we evaluated whether protein-kinase C (PKC), a main regulatory enzyme involved in the mechanism of exocytosis by NK cells, has a role in the cytotoxic response of NK cells (during IL-2 and IFN-beta exposure) from SDAT patients. Our data demonstrate the presence of an increased cytotoxic response by NK cells to IL-2 (mean increase +102%) and IFN-beta (mean increase +132%) in SDAT patients in comparison with healthy elderly subjects (+75% and +88% for IL-2 and IFN-beta, respectively). A smaller suppression of NK cytotoxicity after cortisol was also observed in SDAT (mean decrease -24%) than in the control group (-44%). The NK cell activity of SDAT patients was inversely correlated with the cognitive status as evaluated by the analysis of MMSE (Mini Mental State Examination) score. A comparison of young and elderly healthy subjects revealed no variations in NK cell activity. A physiological decrease in cytosolic PKC activity was demonstrated in healthy old subjects after IL-2 and IFN-beta incubation, but not in SDAT patients, while no variations in kinase activity were observed after cortisol incubation. The decreased activity with cytokines was associated with reduced levels of PKC alpha and betaII isoforms. An alteration in cytokine-mediated NK cell activity associated with PKC dysregulation is therefore suggested to occur in patients with SDAT. These changes may indicate the existence of an immunological component to the pathogenesis and progression of the disease.

Dual mechanisms of apoptosis induction by cytotoxic lymphocytes

Cytotoxic T lymphocytes and natural killer cells together comprise the means by which the immune system detects and rids higher organisms of virus-infected or transformed cells. Although differing considerably in the way they detect foreign or mutated antigens, these cells utilize highly analogous mechanisms for inducing target cell death. Both types of effector lymphocytes utilize two principal contact-dependent cytolytic mechanisms. The first of these, the granule exocytosis mechanism, depends on the synergy of a calcium-dependent pore-forming protein, perforin, and a battery of proteases (granzymes), and it results in penetration by effector molecules into the target cell cytoplasm and nucleus. The second, which requires binding of FasL (CD95L) on the effector cell with trimeric Fas (CD95) molecules on receptive target cells, is calcium independent and functions by generating a death signal at the inner leaflet of the target cell membrane. Exciting recent developments have indicated that both cytolytic mechanisms impinge on an endogenous signaling pathway that is strongly conserved in species as diverse as helminths and humans and dictates the death or survival of all cells.

Activation-induced NK cell death triggered by CD2 stimulation

Both T cells and natural killer (NK) cells express CD2, the target of an alternative activation pathway that induces the proliferation of both cell types. The mitogenic response to CD2 ligation requires the co-expression of CD3:TCR in T cells and FcgammaRIII in NK cells, suggesting that these receptors are involved in transducing the response initiated by CD2. The ability of FcgammaRIII to trigger the activation-induced death of IL-2-primed NK cells led us to investigate the potential for CD2 to trigger activation-induced NK cell death. Our results reveal that the same anti-CD2 monoclonal antibodies (mAb) that activate freshly isolated NK cells induce apoptosis in IL-2-primed NK cells. CD2-induced apoptosis results in chromatin condensation, DNA fragmentation and cleavage of caspase-3. Activation-induced NK cell death triggered by CD2 ligation is extremely rapid (DNA fragmentation is first observed at 90 min) and it is not inhibited by neutralizing antibodies reactive with TNF-alpha or Fas ligand. Whereas mAb reactive with distinct CD2 epitopes (i.e. T11.1, T11.2, and T11.3) are required for activation-induced T cell death, mAb reactive with a single CD2 epitope are sufficient for activation-induced NK cell death. The ability of CD2, CD16, and CD94 to induce apoptosis in IL-2-primed lymphocytes suggests that cytokine priming changes the response to a signaling cascade that is common to each of these activation receptors.

A monoclonal antibody, DL10, which recognizes a sugar moiety of MHC class I antigens expressed on NK cells, NK+ T cells, and granulocytes in humans

One mAb, DL10, was established from mice injected with dolphin lymphocytes. In addition to its reactivity against all dolphin lymphocytes, it reacted with some human leukocytes, including NK cells, NK+ T cells, and granulocytes. When its reactivity was examined in various animals, bovine, ovine, and equine leukocytes were DL10+. Murine, rat, and canine leukocytes were DL10-. Although the reactivity of DL10+ was similar to those of CD56 and CD57 antigens in humans, the actual molecules it recognized were different. Thus, all reactivity of DL10 disappeared after treatment of cells with glycopeptidase or after culture of cells with tunicamycin. Furthermore, the immunoprecipitation method revealed that DL10 indirectly recognized the heavy chain (45kD) of MHC class I antigen in humans and animals. Considering data from analysis of the N-terminal amino acid sequence of the DL10 molecule and the HLA typing of reactive cells, DL10 recognized a sugar moiety of some monomorphic MHC antigens and polymorphic MHC antigens such as HLA-B60 and -B61. If the donors are HLA-B60- and -B61 (> 80% in Japan and > 95% in the United States), DL10 would appear to be a very useful agent for the detection of pan-NK+ T cells.

Biosynthesis, processing and sorting of neutrophil proteins: insight into neutrophil granule development

Neutrophil granulocytes are specialized phagocytic cells that carry a collection of granules for regulated secretion, each with distinct constituents. The granules can be classified as azurophil (primary), developed first, followed in time by specific (secondary) granules gelatinase granules, and secretory vesicles. Stage- and tissue-specific transcription factors govern the successive expression of genes for granule proteins to allow storage of the gene products in these organelle categories whose packaging is separated in time. Many of the granule proteins, in particular those of the heterogeneous lysosome-like azurophil granules, are subject to extensive post-translational proteolytic processing into mature proteins, most commonly as a post-sorting event. A selective aggregation of proteins destined for storage in granules, as discussed in this review, would facilitate their retention and eliminate a need for distinct sorting motifs on each granule protein. Aggregation of granule proteins, that are often cationic, would be assisted by the anionic serglycin proteoglycans present in neutrophils. The antibacterial granule proteins can serve as models for antibiotics and some of them possess a potentially useful therapeutic ability to bind and neutralize endotoxin. Because aberrant expression of transcription factors regulating the synthesis of granule proteins is often found in leukemia, the clarification of mechanisms regulating the timed expression of granule proteins will shed light on the maturation block in myeloid leukemias.

Characterization of B-cell lines from SLE patients and their relatives

Epstein-Barr-virus (EBV)-transformed lymphoblastoid B-cell lines were generated from peripheral blood lymphocytes of 55 patients with systemic lupus erythematosus (SLE) and 44 healthy relatives. All donors have previously been extensively characterized with regard to clinical, serologic, and genetic parameters. Here, peripheral blood lymphocytes and lines were characterized for cell surface antigens. Furthermore, autoantibody production and proliferation rate of the cell lines were monitored. A significant difference between patients and relatives was the lower proliferation rate of EBV-transformed cell lines of the SLE patients. All SLE cell lines are available for interested researches and can be obtained from the European Cell Bank, Salisbury, UK.

Ultrastructure of proteoglycans in the specific granules of guinea-pig basophilic leukocytes as demonstrated by cuprolinic blue staining

The ultrastructure of sulphate proteoglycans in basophil granules was examined using cytochemical procedures designed to stabilize and visualize these highly anionic macromolecules in situ. Unfixed or glutaraldehyde-prefixed guinea-pig spleen cells were submitted to fixation/staining in 2.5% glutaraldehyde, 0.2% cuprolinic blue (CB; a cationic phthalocyanin dye) and 0.2 or 0.3 M MgCl2 with or without glycosidase treatments. Abundant electron-dense precipitates were present throughout the granule matrix. The stained structures were often arranged in a quasi-crystalline typical banded pattern. Negative control basophils had no electrondense precipitates. Digestion with chondroitinase ABC destroyed the CB-positive electron-dense banded or filamentous patterns while sialidase treatment did not, but led to larger CB-positive filaments in the cytoplasm near the granules. Taking into account their high anionicity, as shown by the stability of dye binding in the presence of 0.3 M MgCl2, and their susceptibility to chondroitinase ABC, the CB-precipitates are assumed to be related to the sulphated proteoglycans previously characterized in basophil granules. The CB-positive crystalline or filamentous network of the granule matrix is also assumed to reflect the in situ location and organization of these intracellular proteoglycans and may be involved in maintaining the shape of the granule.

Natural killer cell receptors

In the past year, significant strides have been made in understanding natural killing, the process whereby natural killer cells lyse target cells. Recognition of susceptible targets and activation now appear to be mediated by a natural killer cell receptor that binds carbohydrate determinants on target cells and initiates target lysis. Conversely, receptors have been identified that bind MHC class I molecules on targets that inhibit natural killer cell activation. These findings provide the basis for understanding the molecular processes in the initial steps of natural killing.

The proteoglycan skeleton of the Kurloff body as evidenced by cuprolinic blue staining

This study deals with the ultrastructure of the chondroitin sulphate proteoglycans of the Kurloff body, a large lysosome organelle, metachromatic towards Toluidine Blue, of a blood cell unique to the guinea pig and called the Kurloff cell. Splenic Kurloff cell from oestrogen-treated guinea pig cells were examined after staining with Cuprolinic Blue, a cationic phthalocyanine-like dye, in the presence of MgCl2 in a critical electrolyte concentration method. Better results were obtained when the fixation-staining by the glutaraldehyde Cuprinolinic Blue MgCl2 mixture was preceded by a glutaraldehyde pre-fixation. On light microscopy, Kurloff bodies generally exhibited an overall pink and glassy metachromasia, sometimes with additional darker metachromatic small dots at their peripheries. At the ultrastructural level, the metachromatic central matrix of the Kurloff body usually exhibited, as a major feature, a typical network pattern of ribbon-like or stellate electron-dense precipitates suggesting the presence of a skeleton of Cuprolinic Blue-reactive filamentous structures. Taking into account their high anionicity (as shown by the stability of the dye binding in the presence of 0.3 M MgCl2) and their susceptibility to chondroitinase ABC, these anionic structures were assumed to be related to the proteochondroitin-4-sulphate previously characterized as the only major sulphated glycoconjugate of the Kurloff cell.

Role of leukocyte function-associated antigen-1 and very late antigen-4 in the adhesion and transmigration of c-myc-transfected B-lymphoblastoid cell lines across vascular endothelium

The present study was designed to characterize the adhesive interaction of c-myc-transfected B-lymphoblastoid cell lines with resting and interleukin-1-activated endothelial cells. The transfected cell lines expressed lower levels of leukocyte function-associated antigen-1 compared with control non-transfected lines, while no reduction of expression of other surface structures, including the beta 1 integrin very late antigen-4, was observed. The transfected cell lines adhered to resting or activated endothelial cells less than control cells. Anti-CD18 monoclonal antibody inhibited binding of control cell lines but had a modest or no effect on adhesion of transfected cell lines. Anti-very late antigen-4 monoclonal antibody effectively inhibited binding of both transfected and control cell lines; this was more pronounced in the presence of anti-CD18, suggesting a cooperative interaction between these adhesion pathways. Transfected cell lines also had an impaired ability to penetrate endothelial cell monolayers in a transmigration assay. Our results indicate that activation of the c-myc oncogene in B-cells causes alterations in the adhesive interaction with endothelial cells. This may be relevant in the localization and malignant behavior of B-cell lymphomas carrying an activated c-myc oncogene.

Small proteoglycans

In this review the structure and functions of two non-related proteoglycan families are discussed. One family represents a group of extracellular matrix macromolecules characterized by core proteins with leucine-rich repeat motifs. Within this family special attention is given to those members which carry chondroitin or dermatan sulfate glycosaminoglycan chains. The second family is characterized by repeat sequences of serine and glycine. Their members are products of a single core protein gene and are characteristic constituents of secondary vesicles in cells of the haematopoietic lineage.

Defect of a complement receptor 3 epitope in a patient with systemic lupus erythematosus

Complement receptor 3 (CR3) is expressed on cells of the reticuloendothelial system and involved in the clearance of immune complexes. In this article a patient with a deficiency of the C3bi binding site of this receptor is described. Clinically this patient exhibited predominantly cutaneous manifestations of a systemic lupus erythematosus with an immune vasculitis and panniculitis. The deficiency of the CR3 epitope was demonstrated using flow cytometry. The functional relevance of this defect was demonstrated in a rosetting assay with C3bi-loaded erythrocytes. C3bi binding was found to be significantly decreased. Furthermore, there was an impairment of phagocytosis of opsonized Escherichia coli. The CR3 defect is not due to an autoantibody but is assumed to have a genetic basis. These data suggest that the defect of the CR3 may be involved in the pathogenesis of the immune vasculitis in this patient.

Catecholamines induce alterations of distribution and activity of human natural killer (NK) cells

Catecholamines have been suggested to be responsible for altered cellular immunity after stress. This study was performed to determine the effects of adrenaline and noradrenaline on lymphocyte subpopulations and NK cell functions. Subjects were given a subcutaneous injection of either NaCl, adrenaline (5 micrograms/kg), or noradrenaline (10 micrograms/kg). Catecholamine concentrations, subsets of peripheral blood lymphocytes, NK activity, and antibody-dependent cellular cytotoxicity (ADCC) were analyzed before (baseline) and 5, 15, 30, 60, and 120 min after injection. There were no differences between groups in the distribution of CD2+ and CD8+ lymphocytes over time. However, CD3+ and CD4+ T cells decreased significantly 5 to 60 min after injection of adrenaline. In contrast, NK cell numbers (CD16+, CD56+) increased significantly 5 min after injection of adrenaline and noradrenaline, reached the highest values 15 to 30 min postinjection, and subsequently declined to baseline values 60 (noradrenaline) and 120 (adrenaline) min, respectively, after injection. Similar alterations for NK activity and ADCC were observed after administration of both catecholamines. These data suggest that both sympathetic-adrenal hormones are similarly potent modulators of natural immunity and provide further evidence that catecholamines might be responsible for the observed alterations in immune functions after phases of acute stress.

Small proteoglycans

In this review the structure and functions of two non-related proteoglycan families are discussed. One family represents a group of extracellular matrix macromolecules characterized by core proteins with leucine-rich repeat motifs. Within this family special attention is given to those members which carry chondroitin or dermatan sulfate glycosaminoglycan chains. The second family is characterized by repeat sequences of serine and glycine. Their members are products of a single core protein gene and are characteristic constituents of secretory vesicles in cells of the haematopoietic lineage.

Changes of natural killer cells during acute psychological stress

Emotional stress is often followed by increased susceptibility to infections. One major role in the immediate immune response to infection is played by natural killer (NK) cells. This study was designed to establish whether acute psychological stress influences cellular immune functions and to elucidate the role of endocrine parameters as potent mediators of stress induced alterations of the immune system. Forty-five first-time tandem parachutists were examined continuously for their plasma concentrations of cortisol and catecholamines from 120 min before to 60 min after jumping. Lymphocyte subsets, NK activity, and ADCC were determined 2 hr before, immediately after, and 1 hr after jumping. There was a significant increase in sympathetic-adrenal hormones during (adrenaline, noradrenaline) and shortly after jumping (cortisol). Lymphocyte subsets and the functional capacity of NK cells revealed an increase immediately after jumping followed by a decrease significantly below starting values 1 hr later. These changes were significantly correlated to plasma concentrations of noradrenaline. Thus, quick mobilization of NK cells is suggested as one major mechanism for this effective adaptation of the immune system to stress situations.

Mesangial cell killing by leukocytes: Role of leukocyte oxidants and proteolytic enzymes

Mesangial cells from human and rat kidney were examined for sensitivity to killing by neutrophils. Cells from both species were sensitive to killing by phorbol myristate acetate-stimulated neutrophils. Catalase was highly protective while superoxide dismutase was less protective and a number of protease inhibitors were not protective. Strong protection was also observed with the iron chelators, deferoxamine and phenanthroline, and with the hydroxyl radical scavengers, dimethylthiourea and 5,5-dimethyl-1-pyrroline N-oxide. Pretreatment of the mesangial cells with deferoxamine followed by washing also provided protection. Mesangial cells were also killed by reagent hydrogen peroxide (H2O2) but were much less sensitive to injury by direct application of proteolytic enzymes. The ability of H2O2 to injure mesangial cells was prevented by pre-incubation of the H2O2 with human leukocyte myeloperoxidase. These data suggest that killing is due primarily to the generation of H2O2 by the stimulated neutrophils and its further reduction in an iron-catalyzed reaction. The hydroxyl radical may be the reduction product that actually mediates lethal injury but lack of scavenger specificity prevents definitively concluding this. Mesangial cell killing by activated neutrophils could be significantly inhibited by monoclonal antibodies to CD11/CD18 molecules, suggesting that close contact between the target and effector cells is required for cytotoxicity. Although qualitatively similar to endothelial cells, the mesangial cells appeared to be quantitatively more oxidant sensitive than previously examined human and rat endothelial cells. Taken together, these data show that mesangial cells from rat and human are sensitive to leukocyte-induced injury and that injury results via an oxidant pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning and sequencing of a human cDNA from cytolytic NK/T cells with homology to yeast SEC7

Using the technique of subtractive hybridization (natural killer (NK) minus T helper cell line Jurkat), a human cDNA clone named B2-1 was isolated and sequenced. B2-1 transcripts are highly expressed in NK and peripheral T cells, but not in the T helper cell line used in the subtraction. Two overlapping cDNA clones contained 3309 bp, in agreement with a predicted size of 3.2 kb obtained by Northern blot analysis. The cDNA contained a 5' open reading frame encoding a 398 amino acid (aa) protein with a calculated M(r) of 46,383. The protein contains N-linked glycosylation sites and a site for phosphorylation by protein kinase C. Database homology searches show that the deduced protein is novel and has three discrete domains with significant homology to several structural proteins. The most striking homology was to yeast SEC7 in the central domain of the gene (57% identical over 466 bp) and also the protein level (42% identical amino acids; 39% conserved amino acids). SEC7 is a large protein (2008 amino acids) found on Golgi vesicles that plays a role in protein transport.

Two cytotoxic cell proteinase genes are differentially sensitive to sodium butyrate

The 5'-flanking regions of two cytotoxic cell protease genes, CCP1 and 2, are sufficient to confer cytotoxic T lymphocyte-specific expression when fused to a reporter gene. The two regulatory regions are, however, differentially sensitive to treatment of the recipient cell, MTL 2.8.2, with sodium butyrate. With CCP1 a six-fold increase in cat expression was observed, whereas CCP2 was insensitive to the butyrate treatment. One major butyrate-sensitive regions was defined in the CCP1 5'-flanking sequence between -243 to -112 and another less effective one between-682 to -427. These fragments of DNA were also able to confer responsiveness to butyrate when ligated to a heterologous fos promoter. These sequences within the 5' flank of CCP1 share homology with other elements that have been defined as butyrate-responsive. We believe that our results argue against a pleiotropic affect of butyrate such as histone acetylation. More likely sodium butyrate is mediating a specific stimulation of transcription through modification of the activities of selected transcriptional regulatory proteins that in turn affect their interactions with proteins bound to the promoter.

Proteoglycan synthesis in human erythroleukaemia (HEL) cells

Synthesis of sulphated proteoglycans was compared in human erythroleukaemia (HEL) cells grown under control conditions and under stimulation by dimethyl sulphoxide (DMSO) and phorbol 12-myristate 13-acetate (PMA). Synthesis of [35S]sulphate-labelled proteoglycans by DMSO-treated cells was decreased by about 35% relative to controls, but synthesis of proteoglycans by PMA-treated cells increased 3-4-fold. Control and DMSO-treated cells secreted 65% of the newly synthesized proteoglycans, but PMA-treated cells secreted more than 90%. Sepharose CL-6B chromatography and SDS/PAGE suggested the presence of several proteoglycans in the cells and culture medium. The PMA-treated cells synthesized a low-Mr proteoglycan (Kav. 0.3( that was not present in controls and DMSO-treated cultures. The proteoglycans of the cells and medium from control, DMSO-treated and PMA-treated cultures could be separated into three fractions by octyl-Sepharose chromatography. The proteoglycans were resistant to trypsin but were degraded by Pronase and papain to fragments similar in size to the NaOH/NaBH4-generated glycosaminoglycans. The average chain length of the glycosaminoglycans (Kav. 0.20 on Sepharose CL-6B for controls) was decreased by DMSO (Kav. 0.25) and by PMA (Kav. 0.30-0.38). Chondroitin ABC lyase digestion of the proteoglycans from the medium of the control cultures produced two core proteins at Mr 31,000 and 36,000. The DMSO medium proteoglycans had only the 31,000-Mr core protein, and the PMA culture medium proteoglycans had core proteins of Mr 27,000, 31,000 and 36,000. Changes in synthesis of proteoglycans induced by DMSO or PMA may have relevance for the maturation of haematopoietic cells.

Expression and utilization of chymotrypsin-like but not trypsin-like serine protease enzymes by nonspecific T killer cells activated by anti-CD3 monoclonal antibody

Coculture of purified murine T cells with anti-CD3 monoclonal antibody (145-2C11) results in the induction of nonspecific cytotoxic T lymphocytes (CTL) with MHC-unrestricted cytolytic activity against a range of tumor targets. Serine proteases associated with effector cell granules are among the molecules postulated to play a role in cell-mediated cytolysis. The present study examines the ability of exogenous serine protease substrates to inhibit anti-CD3-activated cytotoxic T (ACT) cell-mediated killing of P815 mastocytoma and YAC1.2 lymphoma target cells. The chymotrypsin substrate N-acetyl-L-tyrosine ethyl ester (ATEE) was found to significantly inhibit ACT cell-mediated cytolysis. In contrast, the trypsin substrate N-benzoyl-L-arginine ethyl ester (BAEE) had little, if any, effect on ACT cell-mediated cytolysis. These effects were observed with both target cell populations. Conjugate inhibition studies performed with ATEE indicated that a chymotrypsin-like serine protease is involved in a postbinding event during cytolysis. Pretreatment of either target or effector cells with ATEE prior to cytolytic assay revealed that the chymotrypsin-like serine protease involved in cytotoxicity is of effector cell origin. Northern blot analysis of total RNA extracted from ACT cells revealed the presence of transcripts coding for CCP1 and CCP2 serine proteases known to be involved in antigen-specific CTL function, but little or no expression of the HF serine protease which has also been implicated in antigen-specific CTL killing. CCP2 exhibits chymotrypsin-like activity while HF displays trypsin-like activity. On the other hand, the CCP1 gene product has protease activity which resembles neither chymase nor tryptase activities. Thus, the level of mRNA expression for these serine proteases is consistent with our earlier observations, using the serine protease substrates, that a chymotrypsin-like serine protease but not a trypsin-like serine protease is involved in ACT cell-mediated cytolysis. "Lymphocyte panning" of ACT cells revealed abundant CCP1 and moderate CCP2 mRNA expression in CD4- and CD8+ anti-CD3-activated T cells with strong tumoricidal activity. CD8- anti-CD3-activated T cells with moderate cytolytic activity also expressed substantial levels of CCP1 and CCP2 mRNA, suggesting that both CD4- CD8- and CD4- CD8+ ACT cells participate in killing tumor targets. In contrast, CD4+ anti-CD3-activated T cells lacked both cytolytic activity and significant CCP1 and CCP2 mRNA expression. These findings are consistent with the involvement of chymotrypsin-like, as well as other, serine proteases in CTL-mediated lysis.