Cell-mediated cytotoxic reactions

Clinicopathological and immunological characteristics of six cats with granular lymphocyte tumors

Clinical and immunological characteristics were investigated in six cases of feline granular lymphocyte (GL) tumor. The ages of the affected cats were relatively old, ranging from 4 to 13 years of age. Gastrointestinal signs were commonly observed in these cases. Only one of the six GL tumor cases was positive for feline leukemia virus (FeLV) antigen. Phenotypic analysis revealed that the GL tumor cells from all of the six cases lacked the T- or B-cell markers. These GL tumor cells were examined by Southern blot analysis using feline immunoglobulin (Ig) and T-cell receptor (TCR) gene probes. GL tumor cells obtained from two cases were identified as cells of T-cell lineage by the presence of a rearranged TCR beta gene, whereas those from the other four cases were considered to be derived from non-T- non-B-cell lineage because of the absence of rearrangement of these genes. These findings indicated that feline GL tumors can be considered as a specific disease entity in feline lymphomas because the cases examined in this study showed onset at an older age, a low incidence of FeLV infection and frequent involvement of gastrointestinal lesions, which are not found in typical FeLV-associated lymphomas. Although no specific phenotypes was observed by phenotypic analysis, the feline GL tumor cells were divided into two consistent genotypes of T-cell or non-T- non-B-cell lineages.

Leucocyte interactions with the mouse cremaster muscle microcirculation in vivo in response to tumour-conditioned medium

Leucocyte interactions with the cremaster muscle microcirculation in vivo were investigated in response to culture medium conditioned with different cell types in 25 adult male Swiss mice. Animals were divided into five groups. Three groups received ex vivo fluorescently labelled lymphokine activated killer (LAK) cells systemically and had either tumour (murine melanoma K1735)-conditioned medium (TCM), fibroblast (murine 3T3)-conditioned medium (FCM) or fresh culture medium administered topically to the cremaster muscle. In the two remaining groups, the host leucocytes were labelled fluorescently by systemic administration of acridine red, and either TCM or FCM was applied topically to the cremaster muscle. There was an immediate but transient increase in the frequency of rolling and adherent LAK cells, and a subsequent (90-120 min later) increase in rolling and adherent host leucocytes, demonstrating temporal differences in the response to topical administration of TCM. These increases in contact with the vascular endothelium occurred in all vessel types, venules, arterioles and capillaries, with the greatest response observed in the venules. The FCM and normal culture medium did not affect the distribution and localization of either LAK cells or host leucocytes. These data suggest that there are one or more soluble tumour-specific chemoattractants for leucocytes present in the conditioned medium. The mouse cremaster muscle microcirculation is therefore a useful model to investigate the mechanism of leucocyte-endothelium interactions in tumour biology.

The role of natural killer cells in the development of herpes simplex virus type 1 induced stromal keratitis in mice

Natural killer (NK) cells and acquired cell-mediated immunity effector cells (delayed type hypersensitivity (DTH) and cytotoxic T lymphocytes (CTL)) have been reported to play a vital role in the defence of the host against tumour and viral infections in locations other than the eye. A vigorous cellular inflammatory response to viral infections of the cornea, however, with the attendant damage to the corneal clarity, has obvious evolutionary disadvantages, and a substantial body of evidence indicates that in animals (e.g. mice) which are highly susceptible to inflammatory destruction of the cornea following corneal encounter with herpes simplex virus, it is the animal's immunological/inflammatory response which is responsible for the corneal damage. We examined the role of natural killer cells in the development of herpes stromal keratitis (HSK) in NK-deficient (C57BL/6J-bgj (beige)) mice and their NK-competent (C57BL/6J (black) relatives. The beige (NK-deficient) mice were just as resistant to HSK as were the black mice. We also studied the effects of NK cell depletion of BALB/c Igh-1 disparate congenic mice. C.AL-20 (Igh-1d) mice are ordinarily highly susceptible to necrotising HSK. In vivo NK-cell depletion in these mice significantly decreased the incidence and severity of HSK in these animals (p < 0.0005). Corneas from untreated C.AL-20 mice contained T cells, macrophages and NK cells. The corneal infiltrate from NK-depleted C.AL-20 mice consisted of T cells and macrophages but no NK cells. These data indicate that NK cells are participants in the development of HSK in the murine model of this disease.

Fc gamma receptor activation induces the tyrosine phosphorylation of both phospholipase C (PLC)-gamma 1 and PLC-gamma 2 in natural killer cells

Crosslinking of the low affinity immunoglobulin G (IgG) Fc receptor (Fc gamma R type III) on natural killer (NK) cells initiates antibody-dependent cellular cytotoxicity. During this process, Fc gamma R stimulation results in the rapid activation of phospholipase C (PLC), which hydrolyzes membrane phosphoinositides, generating inositol-1,4,5-trisphosphate and sn-1,2-diacylglycerol as second messengers. We have recently reported that PLC activation after Fc gamma R stimulation can be inhibited by a protein tyrosine kinase (PTK) inhibitor. Based on the paradigm provided by the receptor tyrosine kinases, we investigated whether PLC-gamma 1 and/or PLC-gamma 2 are expressed in NK cells, and whether the PLC-gamma isoforms are tyrosine phosphorylated in response to Fc gamma R stimulation. Immunoblotting analyses with PLC-gamma 1- and PLC-gamma 2-specific antisera demonstrate that both isoforms are expressed in human NK cells. Furthermore, Fc gamma R crosslinking triggers the tyrosine phosphorylation of both PLC-gamma 1 and PLC-gamma 2 in these cells. Phosphorylation of both isoforms is detectable within 1 min, and returns to basal level within 30 min. Pretreatment with herbimycin A, a PTK inhibitor, blocked the Fc gamma R-induced tyrosine phosphorylation of PLC-gamma 1 and PLC-gamma 2, and the subsequent release of inositol phosphates. These results suggest that Fc gamma R-initiated phosphoinositide turnover in human NK cells is regulated by the tyrosine phosphorylation of PLC-gamma. More broadly, these observations demonstrate that nonreceptor PTK(s) activated by crosslinkage of a multisubunit receptor can phosphorylate both PLC-gamma isoforms.

Accumulation of adoptively transferred adherent, lymphokine-activated killer cells in murine metastases

While close contact between lymphokine-activated killer (LAK)/adherent, lymphokine-activated killer (A-LAK) cells and tumor cells is believed to be a prerequisite for initiating the events leading to tumor cell lysis, clear evidence for the ability of these effector cells to infiltrate tumors or tumor metastases in vivo still has to be obtained. In the present study, we report that a significant fraction of adoptively transferred A-LAK cells, labeled with fluorochromes for identification, accumulates in lung and liver metastases of the B16 melanoma, the MCA 102 sarcoma and the Lewis lung carcinoma lines. Thus, 5- to 10-fold higher numbers of A-LAK cells were found in the malignant lesions compared to the surrounding normal tissue. The infiltration seemed very heterogeneous after intravenous injection of moderate numbers of A-LAK cells (15 x 10(6)). However, after adoptive transfer of 45 million A-LAK cells, an A-LAK cell/tumor cell ratio higher than 1:1 in most metastases was observed. Surprisingly, approximately 5% of the lung metastases seemed totally resistant to infiltration even though neighboring metastases were highly infiltrated. While substantial infiltration of lung metastases was seen after i.v. injection, significant infiltration of liver metastases was seen only after intraportal injection of the A-LAK cells indicating impaired traffic of intravenous injected A-LAK cells through the lung capillaries. These results present direct evidence that A-LAK cells, upon a proper route of administration, have the potential to migrate to and heavily infiltrate metastases from murine tumors of different origin.

T lymphocyte participation in acute serum sickness glomerulonephritis in rabbits

The extent and timing of glomerular T lymphocyte infiltration was studied in acute serum sickness (AcSS) glomerulonephritis (GN) in rabbits. AcSS was initiated by a single intravenous injection of bovine serum albumin (BSA). Rabbits developed circulating BSA anti-BSA immune complexes, and rapid immune elimination of the circulating antigen was associated with the deposition of immune complexes in the kidney and the onset of a diffuse endocapillary proliferative GN. On the day of immune elimination (defined as when less than 1% of the injected antigen remained in the circulation), rabbits developed significant proteinuria (98 +/- 36 mg/24 h; normal 14 +/- 1 mg/24 h, P less than 0.01), glomerular macrophage accumulation (44.3 +/- 21.1 macrophages per glomerulus [mac/glom]; normal 0.28 +/- 0.18 mac/glom, P less than 0.01), and a significant glomerular T lymphocyte influx (3.0 +/- 0.9 cells/glomerular cross-section [c/gcs]; normal 0.47 +/- 0.13 c/gcs; P less than 0.005). On the day prior to immune elimination, increased T cells numbers were observed in some rabbits (2.4 +/- 2.1 c/gcs) together with a minor macrophage presence (7.6 +/- 3.6 mac/glom) and minimal proteinuria (17.6 +/- 3 mg/24 h). These studies demonstrate the influx of T lymphocytes together with macrophages at the onset of proteinuria in serum sickness nephritis and are consistent with a role for cell-mediated immunity in the pathogenesis of this lesion.

Cytotoxic mechanisms of murine lymphokine-activated killer cells: functional and biochemical characterization of homogeneous populations of spleen LAK cells

A highly purified population of murine lymphokine-activated killer (LAK) cells was obtained by selecting plastic-adherent splenocytes after incubation in high doses of recombinant IL-2. The population obtained was shown to be more than 95% positive for the cell marker asialo-GM1, and negative for both Lyt-1 (CD5) and Lyt-2 (CD8). The cells presented typical large granular lymphocyte morphology, and killed NK-susceptible target cells in an exclusively calcium-dependent fashion. A target cell DNA fragmentation activity of LAK cells could be detected even before target cell death. The presence of Hanukkah Factor/granzyme A/serine esterase 1, CTLA-1/granzyme B/serine esterase 2, and pore-forming protein (PFP/perforin) in these LAK cells was demonstrated by Northern blot analysis, suggesting that these markers are not exclusively associated with cytotoxic T lymphocytes. On immunoblots, antibodies specific for a lymphocyte PFP/perforin reacted with a 70-kDa protein of LAK cells. PFP/perforin was localized by immunofluorescence to the cell granules. A 50-kDa protein antigenically related to the macrophage cytokine tumor necrosis factor (TNF) was detected by immunoblotting and localized by immunofluorescence to both the cell granules and the cytosol. No RNA for TNF, however, could be detected using TNF-specific probes, suggesting that LAK cells may contain a cytotoxic factor which is related to, but distinct from, TNF. The work presented here demonstrates that cytotoxic mediators identified in cell lines are also present in primary cell cultures.

Natural killer cytotoxicity in the diagnosis of immune dysfunction: criteria for a reproducible assay

Current evidence indicates that natural killer (NK) cells, which are large granular lymphocytes that mediate non-major histocompatibility complex (MHC)-restricted cytotoxicity and antibody-dependent cytotoxicity and that are involved in multiple regulatory, developmental, and immunologic processes, are important in health. Immunodeficiency states presenting with low NK activity are often associated with malignancies, chronic viral infections, or autoimmune diseases. Monitoring of NK function appears to be indicated as an aid to diagnosis, prognosis, and follow-up after therapy. Reliable performance of NK assays in a clinical laboratory requires that uniform criteria be established and followed for the acceptability of results. Statistical analysis of daily variability can be of great assistance in identifying and tracking sources of error, but routine statistical adjustments are not generally advisable. The quality control program described here provides a degree of assurance that this cytotoxicity assay can be dependable whether performed at one time point or serially. The successful implementation of this program requires laboratory resources, biostatistical support, and interpretative skills, all of which are available in a modern clinical laboratory.

Temporal arteritis: cell composition and the possible pathogenetic role of cell-mediated immunity

A biopsy specimen exhibiting the typical morphologic characteristics of temporal arteritis was studied by using light immunofluorescent, and electron microscopy and immunohistochemical techniques. The granulomatous lesion consisted of clusters of macrophages, epithelioid cells, giant cells, and the peripheral lymphocyte mantle, and was localized mainly in the media. Neutrophils were rare, and fibrinoid necrosis was absent. In immunofluorescent and immunohistochemical studies, no significant deposition of immunoglobulins or complement was observed. Immunohistochemical study with monoclonal antibodies to leukocyte surface antigens demonstrated that the central aggregated granulomatous infiltrate consisted of OKTM1+, Leu-M3+, HLA-DR+ epithelioid macrophages and multinucleated giant cells, whereas OKT8+, HLA-DR+ (suppressor/cytotoxic) T cells predominated in the peripheral lymphocyte mantle. These findings suggest that cell-mediated immunity, especially T cell-regulated granulomatous reaction, may play an important role in the pathogenesis of temporal arteritis. By electron microscopy, smooth muscle cells often exhibited closely attached macrophages, epithelioid cells, and giant cells, and displayed a variety of cell injuries. It therefore seems likely that smooth muscle cells are a primary target of the granulomatous reaction.

Antibacterial activity of human natural killer cells

The in vitro effects of human NK cells on viability of Gram-negative and Gram-positive bacteria was investigated. PBLs depleted of glass-adherent cells showed a significant antibacterial activity that was increased as the concentration of NK cells became higher. Leu-11-enriched cells exhibited the most efficient bactericidal activity. Stimulation of NK cells with staphylococcal enterotoxin B for 16 h produced a significant increase in the antibacterial activity of all NK cells tested. The antibacterial activity of monocyte-depleted cells and Leu-11-enriched cells was also enhanced after culturing in vitro for 16-24 h without exogenous cytokines. Dependence of the antibacterial activity on the presence of serum in the culture medium was not found. Ultrastructural studies revealed close contact between NK cell membranes and bacteria, no evidence of phagocytosis, and extracellular bacterial ghosts, after incubation at 37 degrees C. Supernatants from purified NK cells exhibited potent bactericidal activity with kinetics and target specificity similar to that of effector cells. These results document the potent antibacterial activity of purified NK cells and suggest an extracellular mechanism of killing.

Resistance of cytolytic lymphocytes to perforin-mediated killing. Lack of correlation with complement-associated homologous species restriction

CTL and NK cells resist self-mediated killing and lysis by their own pore-forming protein (PFP; perforin). Perforin, like C, lyses RBC. Efficient C-mediated lysis of RBC occurs when both C and RBC are from different species (homologous species restriction). A protective surface protein (C8-binding protein, homologous restriction factor) has been reported to mediate both homologous species restriction in C-dependent cytolysis and protection of some target cells against perforin-induced lysis. We show here that perforin, unlike C, lyses target cells across a variety of species, including the homologous one, while the same target cell populations resist the attack by homologous C. Perforin-containing extracts of CTL and LAK/NK cells from three species (rat, mouse, and human) and purified mouse perforin were tested against RBC from 10 different species, several nucleated target cell lines, and one primary cell population (thymocytes). While resisting lysis by homologous C, most of these cell types were lysed effectively by perforin without any homologous restriction pattern. CTL and NK cells, like other nucleated targets, are resistant to lysis by homologous but not heterologous C; however, these cell types are resistant to both homologous and heterologous perforin. Together, our results suggest that the protective mechanisms associated with C- and perforin-mediated lysis are distinct.

Isolation and sequence analysis of serine protease cDNAs from mouse cytolytic T lymphocytes

Three new cDNA clones (designated MCSP-1, MCSP-2, and MCSP-3) encoding mouse serine proteases were isolated from cloned cytolytic T lymphocytes (CTL) by a modified differential screening procedure. The putative mature proteins of MCSP-2 and MCSP-3 are each composed of 228 amino acids with molecular weights of 25,477 and 25,360, respectively. NH2-terminal amino acids of MCSP-2- and MCSP-3-predicted proteins were identical to those reported for granzyme E and F, respectively. The third species, MCSP-1, was closely related to the two other cDNA species but approximately 30 amino acids equivalents of the NH2-terminal portion of the cDNA were not cloned. The amino acids forming the active sites of serine proteases were well conserved among the three predicted proteins. The active site pocket residue positioned six residues before the active-site Ser184 is alanine in MCSP-1, threonine in MCSP-2, and serine in MCSP-3, indicating that both MCSP-2 and MCSP-3 may have chymotrypsin-like specificity. There are three potential asparagine-linked glycosylation sites in MCSP-1 and MCSP-3, and four in MCSP-2-deduced amino acid sequences. Amino acid comparison of MCSP-1 with four other reported serine proteases whose active site pocket residue is alanine revealed that MCSP-1 was substantially different from the other molecules, indicating that MCSP-1 may be a new member of mouse T cell serine protease family. Antibodies made against a MCSP-1 lacZ gene fusion protein stain granules of CTL and react on immunoblots with two distinct granule protein bands of 29 and 35-40 kD. Only the 35-kD species labels with [3H]DFP. Since a protease cascade may play a key role in cytolytic lymphocyte activation, our isolation of cDNAs representative of unique serine esterases should help to investigate such a cascade process.

Perforin-dependent and -independent pathways of cytotoxicity mediated by lymphocytes

There is little doubt at the present time that both perforin-dependent and -independent pathways are important in mediating the cytotoxicity associated with lymphocytes. The cell distribution of perforin, initially thought to include both CTL and NK cells, now must be viewed with caution because all previous biochemical studies on CTL have been conducted with cell lines propagated in long-term cultures in the presence of T cell growth factors (IL-2 and perhaps some still undefined factors). Under these conditions, CTL are known to assume a broader, NK-like specificity in target cell killing and may thus differ significantly from primary CTL generated in the body. Accordingly, perforin does not seem to be present in primary CTL activated directly through mixed lymphocyte reactions. It remains to be shown how primary CTL lyse target cells in vivo. Initial studies conducted in several laboratories have already provided some clues. It now seems that even in cultured, perforin-containing CTL, the perforin pathway is not an obligatory mechanism required for target cell killing. Other pathways, possibly involving TNF/lymphotoxin-like molecules, may play a direct role in this type of cytotoxicity. Other still unidentified factors now also need to be sought, including membrane polypeptides that may develop cytotoxicity directly upon cell contact and binding. Although from the studies reviewed here it is clear now that perforin has a more limited role in cell killing than originally proposed, it is still intriguing that it should share structural and functional homologies with complement proteins, drawing paradoxical analogies between two systems (the cellular and the humoral immune systems) which have evolved to become specialized to carry out separate immunological tasks. The cloning of the genes for perforin and for all the C proteins that comprise the MAC should reveal important information on how these genes originated and then diverged during evolution. The cellular distribution of other granule products, such as serine esterases, also must be viewed with caution. A serine esterase activity was initially thought to be CTL-specific. This information stimulated an intensive research activity in many laboratories that resulted in both the purification of a serine esterase family and the cloning of several serine esterase transcripts. It is becoming clear from recent evidence that this group of enzymes is not truly CTL-specific and therefore would not be expected to develop any function rendered absolutely necessary for cytolysis.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification, isolation, and characterization of a novel cytotoxin in murine cytolytic lymphocytes

Murine cytotoxic T lymphocytes contain, in addition to the cytotoxic pore-forming protein perforin, another cytolytic factor localized in both cytoplasm and granules. Like perforin, this CTL cytotoxin lyses a variety of tumor cells; unlike perforin, it is stable in the presence of calcium, requires several hours to induce maximal lytic activity, and is antigenically related to the previously described tumor necrosis factor (TNF) and lymphotoxin (LT). However, it differs from TNF and LT in a number of biochemical and functional properties. TNF- and LT-specific cDNA probes did not hybridize with any CTL-specific message, indicating that the CTL cytotoxin is distinct from those two factors. It has an apparent Mr of 50 and 70 kd under reducing and nonreducing conditions, respectively, is secreted by secretagogue-stimulated CTLs, and causes DNA fragmentation in several targets, a phenomenon previously attributed to target cell damage by CTLs. These results suggest that killing by lymphocytes may encompass multiple mechanisms and polypeptides.

Identification and characterization of a pore-forming protein of human peripheral blood natural killer cells

We show here that human peripheral blood NK cells contain a pore-forming protein (PFP) with an Mr of 70,000-72,000 that assembles structural lesions (with an average internal diameter of 150-170 A) and forms functional channels. The PFP was isolated by affinity chromatography from human NK cells, using a specific anti-C9 antiserum as the immunoadsorbent. The NK cells were isolated from PBL by positive or negative selection by indirect rosetting using a panel of monoclonal antibodies directed against different NK and T cell surface antigens. PFP was identified in NK cells freshly isolated and isolated from cultured PBL, both stimulated with interleukin 2, but not in NK cell-depleted lymphocytes. In planar bilayers, the channels formed by the NK cell-derived PFP are highly voltage resistant, with most channels persisting in the open state once they have inserted into the bilayer. The unit conductances of these channels range 0.3-1 nS in 0.1 M NaCl. The channels show poor selectivity for monovalent and divalent ions. The PFP is also released from human NK cells stimulated with the calcium ionophore A23187, suggesting that this protein, like the one produced by murine CTL lines, may be similarly secreted during cell-mediated killing. Its identification in primary human NK cell cultures indicates that this protein may play an active role in NK cell-mediated killing.

Isolation and characterization of a serine esterase from cytolytic T cell granules

Cytotoxic T lymphocytes and lymphocytes with NK-like activity contain a serine esterase activity which has been localized to their cytoplasmic granules by cytochemistry and subcellular fractionation studies. The serine esterase-specific inhibitor 3H-DFP labels two protein species in the granules. The two proteins, referred to as serine esterases 1 and 2 (SE 1 and SE 2), migrate with Mr of 34-36 kd and 28-30 kd, respectively, under reducing conditions. SE 1 shows trypsin-like activity and has been purified to apparent homogeneity. Under nonreducing conditions, SE 1 has an Mr of 60-66 kd, suggesting that it may consist of two disulfide-linked subunits of 34-36 kd each. SE 1 cleaves fibrin and casein, has a pl greater than 10, and optimal activity at pH 8. The substrate specificity of SE 2 is not known. The serine esterase activity is secreted by lymphocytes that have been stimulated with the calcium ionophore A23187. The serine esterases described here could play an active role in cell-mediated killing.