Perforin and serine esterase gene expression in stimulated human T cells. Kinetics, mitogen requirements, and effects of cyclosporin A

Cytokine modulation of cell growth and role in tumour therapy

Cytokines are a group of secreted proteins which act as intracellular signals co-ordinating the growth and function of cells in the haematopoietic systems. Despite often overlapping functions they appear to have evolved separately but their receptors do share several features suggesting a common ancestor. Taking interleukin 2 (IL2) as an example we discuss the mechanisms involved with the regulation of IL2, the interleukin 2 receptor (IL2R) and their modes of action. Finally we discuss the various aspects of cytokines which allow their use as antitumour agents.

BLT esterase activity as an alternative to chromium release in cytotoxic T cell assays

Granules released by cytotoxic T cells (CTL), during recognition and killing of target cells, contain granule enzyme A. This serine protease has an esterase activity, which is easily measured using the substrate benzyloxycarbonyl-L-lysine thiobenzyl ester (BLT). BLT activity, routinely used as an assay for granule release, provides an alternative to the standard chromium release assay as a measure of CTL-mediated killing. The two methods were highly comparable when either exogenous synthetic peptide or endogenously produced epitopes were used as targets and human CTL clones acted as effectors. The advantages of the BLT assay are that it uses inexpensive non-radioactive reagents, the assay can be run over any period between 4 and 30 h and can be performed with as few as 10(4) CTLs if synthetic peptide epitopes are used.

Expression of T-cell-associated serine proteinase 1 during murine Leishmania major infection correlates with susceptibility to disease

The expression of T-cell-associated serine proteinase 1 (MTSP-1) in vivo during Leishmania major infection was analyzed in genetically resistant C57BL/6 mice and in genetically susceptible BALB/c mice. Using a monoclonal antibody as well as an RNA probe specific for MTSP-1 to stain tissue sections, we found T cells expressing MTSP-1 in skin lesions and spleens of mice of both strains. In skin lesions, MTSP-1-positive T cells could be detected as early as 3 days after infection. Most importantly, the frequency of T cells expressing MTSP-1 was significantly higher in susceptible BALB/c mice than in resistant C57BL/6 mice. These findings suggest that MTSP-1 is associated with disease-promoting T cells and that it may be an effector molecule involved in the pathogenesis of cutaneous leishmaniasis.

Induction of members of the IL-8/NAP-1 gene family in human T lymphocytes is suppressed by cyclosporin A

Human members of a family of structurally related cytokines, which play a role as effectors of inflammation, were analyzed for their expression and regulation in T lymphocytes. Members of this gene family include Platelet Basic Protein (PBP); Platelet Factor 4 (PF-4); IL-8/NAP-1; IP-10, a gamma interferon induced protein; GRO; pAT 464 and pAT 744. In resting T lymphocytes the RNAs of the individual genes could not be detected, but all genes were induced upon stimulation with PHA or with PHA/PMA. The induction of five genes was blocked by the immunosuppresive drug cyclosporin A (CSA), which appears to affect initial events in T cell activation. This expression in T lymphocytes, especially the sensitivity to CSA, indicates a common immunmodulatory role of these structural related proteins.

Expression of perforin and granzymes in vivo: potential diagnostic markers for activated cytotoxic cells

Perforin and granzymes are considered to be instrumental in cell-mediated cytolysis by cytotoxic T cells and natural killer cells. Here, Gillian Griffiths and Christoph Mueller describe the expression of perforin and granzymes, emphasizing studies in vivo, and discuss the possibility that these proteins are useful diagnostic markers for immune responses involving cytolytic cells.

Perforin mRNA expression in the inflamed tissues of NZB/W F1 lupus mice decreases with methylprednisolone treatment

Perforin is one of the important cytolytic factors in cytotoxic T lymphocytes (CTL) and natural killer (NK) cells. In this study, the authors examined perforin mRNA levels in the kidney, spleen, liver, lung, heart, and brain of NZB/W F1 lupus mice and NZW mice. Perforin mRNA levels in the kidney, spleen, liver, and lung of NZB/W F1 mice increased significantly with age, whereas those in the heart and brain of NZB/W F1 mice showed little change between 2 and 10 months of age. In all tissues examined in NZW, control mice perforin mRNA levels showed little change during the experimental period. In addition, the authors examined the effect of methylprednisolone (MPSL) on perforin gene expression in the tissues of NZB/W F1 mice. MPSL ameliorated the increase in perforin mRNA levels in the kidney, spleen, liver, and lung of NZB/W F1 mice. These findings suggest that perforin may contribute to tissue injuries in autoimmune lupus mice and that MPSL may be effective in lupus partly by decreasing perforin expression.

The distribution of perforin in normal tissues

We describe the production of monoclonal antibodies to murine and human forms of the lymphocyte pore-forming protein (perforin, PFP, or cytolysin), a major granule-localized cytolytic mediator of CTL and NK cells. Antibodies were raised against both murine perforin purified from a CTL line, and human perforin expressed in bacteria as a fusion protein with the Escherichia coli TrpE protein. Antibodies raised against either immunogen inhibited the hemolytic activity of murine perforin, and thus may enable us to identify the pore-forming or self-associative domain of perforin. One mAb, MP1, was used to study the distribution of perforin in murine tissues under physiological conditions. We found that perforin was expressed in the granular metrial gland (GMG) cells of the pregnant murine uterus, but not in other tissues examined. These results further support the view that perforin is induced only in activated cytolytic lymphocytes, and raise the question whether perforin-containing GMG cells represent an effector of a maternal immune response to the fetus.

T-cell-mediated cytotoxicity

There are two competing theories to explain the mechanism(s) by which cytolytic T lymphocytes kill target cells: granule exocytosis of a pore-forming protein, and contact-induced internal disintegration. Accumulated evidence supports alternative pathways in lymphocytoxicity, possibly reflecting distinct effector functions expressed by different killer cells and cells at different stages of activation.

Granzyme A and perforin as markers for rejection in cardiac transplantation

The use of granzyme A and perforin as markers for rejection after cardiac transplantation has been investigated. Using in situ hybridization we have detected lymphocytes expressing granzyme A and perforin RNA that are infiltrating the donor heart after transplantation. A total of 29 different biopsies from 17 different patients who had undergone cardiac transplantation were examined. Twelve biopsies classified by conventional histological criteria as showing evidence of rejection were found to contain lymphocytes expressing granzyme A and perforin. Seven biopsies classified as showing no histological evidence of rejection infiltrating lymphocytes were found not to be expressing granzyme A or perforin. However, in 10 other biopsies from 5 different patients that had been classified as showing no evidence of rejection by the conventional grading system, lymphocytes expressing granzyme A and perforin were detected. In six of these cases the patient was found to have undergone a subsequent rejection episode. In the other four cases the biopsies were either taken at a very early stage after transplantation and the high doses of immunosuppression used routinely at that stage are likely to have averted any rejection episodes, or it was not possible to follow subsequent rejection episodes. These results, which are statistically significant (p = 0.06), demonstrate that granzyme A- and perforin-expressing lymphocytes can be identified in rejecting biopsies before histological damage is seen. The identification of perforin and granzyme A expression in vivo suggest a possible role for these proteins in the cytolysis that occurs during transplantation rejection. Furthermore, the data presented here suggest that it may be possible to use granzyme A and perforin as early predictive markers of transplantation rejection.

Expression of perforin and serine esterases by human gamma/delta T cells

gamma/delta T cells have recently been described in association with a number of disorders, including autoimmune diseases. gamma/delta T cells are thought to play a cytotoxic role, but their mechanism of action is not known. Several granule mediators of cytotoxicity, including a pore-forming protein (perforin), and a family of serine esterases, have been isolated from cytotoxic T lymphocytes (CTL), lymphokine-activated killer (LAK) cells, and natural killer (NK) cells. We demonstrate here that gamma/delta T cells also express these mediators. Northern blots show that gamma/delta T cells express perforin, serine esterase 1 (SE 1), and SE 2. Three polyclonal antisera - raised against murine perforin, a peptide composed of amino acids 1-34 of human perforin, and human peforin expressed in bacteria - all reacted with a 70-kD protein in gamma/delta T cells on Western blots. Immunostaining with antiperforin antisera shows that primary gamma/delta T cells also contain perforin. Electron microscopy reveals that the granules of gamma/delta T cells resemble those of CTL, LAK, and NK cells. Gamma/delta T cells also resemble LAK cells in possessing inclusion bodies in their nuclei. These results imply that gamma/delta T cells resemble other cytolytic lymphocytes in their mechanism of action.

Novel putative promoter/enhancer sequences are shared by the mouse and human perforin (Pfp) genes

This report describes the organization of the mouse pore-forming protein (perforin) gene (Pfp), which is highly analogous to that of the corresponding human gene. Pfp comprises three exons, the first of which consists entirely of 5' non-coding sequence, separated by an intron of 1.94 kb from the two polypeptide-coding exons. The promoter region of the gene shows strong similarity to that in humans, with six stretches of high homology noted within 0.7 kb of the mRNA cap site. However, many of the sequences of the human gene with similarity to previously described promoter/enhancer elements are poorly conserved in the mouse, suggesting that these motifs may be of no functional significance, and that control mechanisms for expression of Pfp may be highly specific to killer cells.

Age-related decrement in cytotoxic T lymphocyte (CTL) activity is associated with decreased levels of mRNA encoded by two CTL-associated serine esterase genes and the perforin gene in mice

The age-related decline in cytotoxic T lymphocyte (CTL) activity has been recognized for many years. Age-related alterations in several immunologic events have been suggested to be partly or completely responsible for this decline. We had previously demonstrated (Bloom et al., Cell. Immunol. 1988. 144: 440) in mice that a deterioration in the lytic mechanism may be at least in part responsible for the decline in CTL activity. We now report that this decline correlates with an age-related decrease in serine esterase activity released into the supernatant medium in the process of generating CTL. Northern analyses were then used to examine the effect of age on expression of genes encoding for perforin and two CTL-associated serine esterases. The products of all three of these genes have all been postulated to play roles in CTL-mediated lysis. We show that the expression of all three of these genes appears to decline with age in the process of generating allogeneic CTL. These alterations in gene expression correlated both with diminished cytolytic and released esterase activities generated by mixed leukocyte culture in spleen cells of old mice compared to young. The age-related decline in gene expression could not be attributed to shifts in T cell subsets, but CD8+ cells generated by allogeneic stimulation of nylon wool-passed spleen cells from old mice expressed significantly less cytolytic activity than those from young. This report is the first demonstration of an age-related decrease in expression of a functionally related group of genes. In addition, these findings are compatible with the suggested roles for perforin and serine esterase release in CTL-mediated target cell lysis.

Stimulation of cloned human T lymphocytes via the CD3 or CD28 molecules induces enhancement in vascular endothelial permeability to macromolecules with participation of type-1 and type-2 intercellular adhesion pathways

Perivascular accumulation of CD29+CD45R0+ memory T lymphocytes at sites of chronic inflammation such as rheumatoid synovium is commonly associated with the localized increase in the endothelial permeability. We have recently demonstrated that a direct interaction between activated CD29+CD45R0+ memory T lymphocytes and vascular endothelial cells (EC) results in the increased permeability of EC. In this report, we have investigated effects on antigen-specific T cell receptor (TcR) alpha/beta+ human T lymphocyte clones on the endothelial permeability to albumin. Our results show that CD29+CD45R0+ cloned human T lymphocytes augment endothelial permeability by a noncytolytic process requiring surface contact between T lymphocytes and EC. Both cytolytic and noncytolytic cloned T lymphocytes were capable of augmenting endothelial permeability and this process did not involve active lysis of EC. Stimulation of T lymphocytes via the CD3/TcR or CD28 molecules resulted in significant enhancement in the ability of T lymphocytes to influence endothelial permeability. Pretreatment of T lymphocytes with monoclonal antibodies directed at either CD11a/CD18 (LFA-1) or CD2 molecules or that of EC with monoclonal antibodies directed at either CD54 (ICAM-1) or CD58 (LFA-3) molecules significantly inhibited T lymphocyte-induced enhancement in endothelial permeability, thus indicating that activated T lymphocytes utilize both type-1 (CD11a/CD18CD54) and type-2 (CD2CD58) intercellular adhesion pathways to augment endothelial permeability and signals received via CD3 or CD28 molecules on T lymphocytes further enhance this process. Furthermore, proinflammatory cytokines interleukin 1 and tumor necrosis factor but not proinflammatory cytokines interleukin 1 and tumor necrosis factor but not interleukin 6 induced resistance in EC to T lymphocyte-mediated effects on their permeability. Collectively, these observations may provide insights into molecular mechanism(s) underlying pathophysiology of localized chronic inflammatory responses in general and more specifically selective accumulation of chronically activated memory T lymphocytes at sites of chronic inflammation.

Characterization of a novel, human cytotoxic lymphocyte-specific serine protease cDNA clone (CSP-C)

A human cDNA clone encoding a novel serine protease, cytotoxic serine protease-C(CSP-C), has been isolated from a cDNA library prepared from recombinant interleukin-2 (IL-2)-activated lymphocytes of a patient with a large granular lymphoproliferative disorder. The clone has a 741-base pair open reading frame encoding a putative 246-amino acid protein. The protein sequence contains the catalytic charge relay system characteristic of a serine protease and the conserved N-terminal amino acid sequence of the mature cytotoxic lymphocyte serine proteases found in both mouse and human. The amino acid sequence of CSP-C has 71% identity with the previously reported cytotoxic serine protease-B(CSP-B)/human lymphocyte protease (HLP)/SECT and 57% identity with the granulocyte-specific serine protease cathepsin G. The homology with another lymphocyte-specific serine protease, human Hanukah factor (HF)/Granzyme A was 41%. The transcript is expressed in lymphocytes stimulated with IL-2 or IL-2 plus phytohemagglutinin (PHA). CSP-C is not expressed in B-lymphoblastoid cell lines or in the T-leukemia cell line MOLT4. The cDNA sequence suggests that the protein is expressed as a prepropeptide, as has been found in the other murine and human serine proteases of lymphocyte origin. It has recently been reported that human chromosome 14q11, in addition to containing the genes encoding cytotoxic serine protease B (CSP-B), cathepsin G, and the T-cell receptor alpha and delta genes, also includes an additional genomic DNA clone which cross-hybridized with CSP-B and cathepsin G, cathepsin-like gene-2 (CGL-2). It is likely that the CSP-C cDNA clone reported in this study corresponds to CGL-2.

Genomic organization of the mouse pore-forming protein (perforin) gene and localization to chromosome 10. Similarities to and differences from C9

Genomic clones encompassing the entire coding region of the mouse lymphocyte pore-forming protein gene (Pfp) have been isolated and used to determine its intron-exon organization. In contrast to C9, Pfp has a simple structure, consisting of only three exons (two of which encode polypeptide), a large 5' intron, and a single, smaller intron that is situated approximately one-third of the way through the protein-coding portions of the gene. The regions encoding the homologous domains of PFP and C9 are encoded on exons 7, 8, 9, and 10 of C9, but form only approximately half of the open reading frame of exon III in Pfp. Although encoding polypeptides with related functions, the two genes possess such sharply contrasting structures as to suggest that their analogous regions may have risen independently, by a process of convergent evolution. Using a panel of somatic cell hybrid cell lines, Pfp has been mapped to chromosome 10.