Chemotherapy remains one of the irreplaceable treatments for cancer therapy.The use of immunogenic cell death(ICD)-inducing chemotherapeutic drugs offers a practical strategy for killing cancer cells,simultaneously el...Chemotherapy remains one of the irreplaceable treatments for cancer therapy.The use of immunogenic cell death(ICD)-inducing chemotherapeutic drugs offers a practical strategy for killing cancer cells,simultaneously eliciting an antitumor immune response by promoting the recruitment of cytotoxic immune cells and production of granzyme B(GrB).However,numerous malignant cancers adaptively acquired the capacity of secreting serpinb9(Sb9),a physiological inhibitor of GrB,which can reversibly inhibit the biological activity of GrB.To circumvent this dilemma,in this study,an integrated tailor-made nanomedicine composed of tumor-targeting peptide(Arg-Gly-Asp,RGD)decorated liposome,doxorubicin(DOX,an effective ICD inducer),and the compound 3034(an inhibitor of Sb9),is developed(termed as D3RL)for breast cancer chemo-immunotherapy.In vitro and in vivo studies show that D3RL can directly kill tumor cells and trigger the host immune response by inducing ICD.Meanwhile,D3RL can competitively relieve the inhibition of Sb9 to GrB.The restored GrB can not only effectively induce tumor immunotherapy,but also degrade matrix components in the tumor microenvironment,consequently improving the infiltration of immune cells and the penetration of nanomedicines,which in return enhance the combined antitumor effect.Taken together,this work develops an integrated therapeutic solution for targeted production and restoration of GrB to achieve a combined chemo-immunotherapy for breast cancer.展开更多
Human umbilical cord blood (CB) has recently been used as a source of stem cells in transplantation. NK cells derived from CB are the key effector cells involved in graft-versus-host disease (GVHD) and graft-versu...Human umbilical cord blood (CB) has recently been used as a source of stem cells in transplantation. NK cells derived from CB are the key effector cells involved in graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL). It was reported that the activity of CB NK cells was lower than that of adult peripheral blood (PB) NK cells. In this study, we analyzed the expression of some NK cell receptors and cytotoxicity-related molecules in CB and PB NK cells. The expressions of activating NK receptors, CD16, NKG2D and NKp46, did not show significant difference between CB and PB NK cells. But the expression of inhibitory receptor NKG2A/CD94 was significantly higher on CB NK cells. As to the effector function molecules, granzyme B was expressed significantly lower in CB NK cells, but the expressions of intracellular perforin, IFN-γ, TNF-α and cell surface FasL and TRAIL did not show difference between CB and PB NK cells. The results indicated that the high expression of NKG2A/CD94 and low expression of granzyme B may be related with the reduced activity of CB NK cells.展开更多
Apoptotic cell death plays an important role in the maintenance of the normal physiological state and in the pathogenesis of diseases.Granule exocytosis is the main pathway for the immune elimination of virus-infected...Apoptotic cell death plays an important role in the maintenance of the normal physiological state and in the pathogenesis of diseases.Granule exocytosis is the main pathway for the immune elimination of virus-infected cells and tumor cells by cytotoxic T lymphocytes and natural killer cells.In recent study,we have investigated the level of granzyme H in patients with breast cancer and in control subjects using enzymatic method.Our study also included the prediction of different sites of granzyme H that play a role in substrate and inhibitor recognition in apoptosis process by using 3D structural model of the enzyme.The research described the possible post-translational modification sites that may help the enzyme in immune elimination of tumor cells.Our study shows that the level of granzyme H was reduced in patients when compared to normal control subjects.There are a number of amino acids that function as substrate recognition sites in granzyme H.However,inhibitors may inhibit their activity and affect the process of autolysis.展开更多
AIM Several triggering receptors have beendescribed to be involved in natural killer(NK)cell-mediated target cytotoxicity.In these studies,NKcells derived from blood or spleen were used.Pitcells are liver-specific N...AIM Several triggering receptors have beendescribed to be involved in natural killer(NK)cell-mediated target cytotoxicity.In these studies,NKcells derived from blood or spleen were used.Pitcells are liver-specific NK cells that possess ahigher level of natural cytotoxicity and a differentmorphology when compared to blood NK cells.The aim of this study was to characterize the roleof the NK-triggering molecules NKR-P1A,ANK61antigen,and CD45 in pit cell-mediated killing oftarget cells.METHODS <sup>51</sup>Cr-release and DNA fragmentationwere used to quantify target cell lysis andapoptosis,respectively.RESULTS Flow cytometric analysis showed thatpit cells expressed CD45,NKR-P1A,and ANK61antigen.Treatment of pit cells with monoclonalantibody(mAb)to CD45(ANK74)not onlyinhibited CC531s or YAC-1 target lysis but alsoapoptosis induced by pit cells.The mAbs to NKR-P1A(3.2.3)and ANK61 antigen(ANK61)had no effect on pit cell-mediated CC531s or YAC-1 targetcytolysis or apoptosis,while they did increase theFcγ receptor positive(FcγR<sup>+</sup>)P815 cytolysis andapoptosis.This enhanced cytotoxicity could beinhibited by 3,4-dichloroisocoumarin,an inhibitorof granzymes.CONCLUSION These results indicate that CD45participates in pit cell-mediated CC531s and YAC-1target cytolysis and apoptosis.NKR-P1A andANK61 antigen on pit cells function as activationstructures against FcγR<sup>+</sup> P815 cells,which wasmediated by the perforin/granzyme pathway.展开更多
Despite the introduction of potent immunosuppressive medications within recent decades, acute rejection still accounts for up to 12% of all graft losses, and is generally associated with an increased risk of late graf...Despite the introduction of potent immunosuppressive medications within recent decades, acute rejection still accounts for up to 12% of all graft losses, and is generally associated with an increased risk of late graft failure. Current detection of acute rejection relies on frequent monitoring of the serum creatinine followed by a diagnostic renal biopsy. This strategy is flawed since an alteration in the serum creatinine is a late clinical event and significant irreversible histologic damage has often already occurred. Furthermore, biopsies are invasive procedures that carry their own inherent risk. The discovery of non-invasive urinary biomarkers to help diagnose acute rejection has been the subject of a significant amount of investigation. We review the literature on urinary biomarkers here, focusing on specific markers perforin and granzyme B m RNAs, FOXP3 m RNA, CXCL9/CXCL10 and mi RNAs. These and other biomarkers are not yet widely used in clinical settings, but our review of the literature suggests that biomarkers may correlate with biopsy findings and provide an important early indicator of rejection, allowing more rapid treatment and better graft survival.展开更多
Objective: To achieve the co-expression of GrB and PFP in Hep-2 cells and analyze the growth inhibiting effects on Hep-2 cells. Methods: Lymphocytes were separated from human laryngeal carcinoma tissue, complete Exo...Objective: To achieve the co-expression of GrB and PFP in Hep-2 cells and analyze the growth inhibiting effects on Hep-2 cells. Methods: Lymphocytes were separated from human laryngeal carcinoma tissue, complete Exon fragments of GrB and PFP were amplified by RT-PCR via extracting lymphocytes total RNA, and they were recombined to the downstream of T7 promoter in the vector pVAX1. The recombinant plasmid pVAX1-PIG was transfected into Hep-2 cells with Lipofectamine 2000. The expression of proteins was identified by RT-PCR, MTT and western blot assay. Results: The gene sequence of the RT-PCR products of GrB and PFP were consistent with the data of GenBank by DNA sequencing analysis. The GrB and PFP cDNA fragment were cloned into the vector of pVAX1 in the right direction and the open reading fragment of GrB and PFP were maintained. The target proteins were detected in the transfected Hep-2 cells, and the inhibitive effect of PFP and GrB on Hep-2 cells growth were studied by thiazolyl blue (MTT) test. Conclusion: The pVAX1-PFP-IRES-GrB plasmid was successfully constructed and expressed, and the expression of PFP and GrB could inhibit the growth of Hep-2 cells.展开更多
Vaccines have been shown to cause differential expression of genes and increase antibody titers against antigens. Influenza vaccines may have an effect on unexplained disorders such as Chronic Fatigue Syndrome/Myalgic...Vaccines have been shown to cause differential expression of genes and increase antibody titers against antigens. Influenza vaccines may have an effect on unexplained disorders such as Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME). Immunological changes have been identified following immunization with trivalent influenza vaccine (TIV). The objective of this pilot study was to examine the consequences of TIV on cytokine and cytotoxic genes in CFS/ME. Peripheral blood mononuclear cells were preferentially isolated from whole blood of 7 CFS/ME patients and 8 controls. Following total RNA extraction and synthesis of cDNA, reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) was used to determine the expression levels of mRNAs for cytotoxic genes (perforin (PRF1), granzyme A (GZMA), granzyme B (GZMB) and cytokine genes. GZMB was significantly increased overall in the CFS/ME patients compared to the controls. GZMA was significantly increased 28 days after vaccination while PRF1 was reduced prevaccination but increased 14 days post-vaccination in the CFS/ME patients. There were no significant changes in cytokine genes pre or post vaccination. Administration of TIV may increase the expression of lytic genes in CFS/ME and this may contribute to the increase in cytotoxic activity we observed in these patients post vaccination.展开更多
Dengue virus (DENV) remains a major public health threat because no vaccine or drugs are available for the prevention and treatment of DENV infection, and the immunopathogenesis mechanisms of DENV infection are not ...Dengue virus (DENV) remains a major public health threat because no vaccine or drugs are available for the prevention and treatment of DENV infection, and the immunopathogenesis mechanisms of DENV infection are not fully understood. Cytotoxic molecules, such as granzyme B (GrzB), may be necessary to control viral infections. However, the exact role of GrzB during DENV infection and the mechanisms regulating GrzB expression during DENV infection are not clear. This study found that miR-27a~, miR-3Oe, and miR-378 were down-regulated in DENV-infected patients, and DENV infection in humans induced a significant up-regulation of GrzB in natural killer (NK) cells and CD8+ T cells. Further investigation indicated that NK cells, but not CD8+ T cells, were the major sources of GrzB, and miR-378, but not miR-27a~ or miR-3Oe, suppressed GrzB expression in NK cells. Notably, we found that overexpression of miR-378 using a miR-378 agomir in DENV-infected mice inhibited GrzB expression and promoted DENV replication. These results suggest the critical importance of miR-378 in the regulation of GrzB expression and a protective role for GrzB in controlling DENV replication in vivo. Therefore, this study provides a new insight into the immunopathogenesis mechanism of DENV infection and a biological basis for the development of new therapeutic strategies to control DENV infection.展开更多
Dimethyl fumarate (DMF) is a new drug used to treat multiple sclerosis (MS) patients. Here, we examined the effects of DMF and the DMF metabolite monomethyl fumarate (MMF) on various activities of natural killer...Dimethyl fumarate (DMF) is a new drug used to treat multiple sclerosis (MS) patients. Here, we examined the effects of DMF and the DMF metabolite monomethyl fumarate (MMF) on various activities of natural killer (NK) cells. We demonstrated that MMF augments the primary CD56^+, but not CD56^-, NK cell lysis of K562 and RAJI tumor cells. MMF induced NKp46 expression on the surface of CD56^+, but not CD56^-, NK cells after incubation for 24 h. This effect was closely correlated with the upregulation of CD107a expression on the surface of CD56+ NK cells and the induction of Granzyme B release from these cells through this metabolite. An anti-NKp46 antibody inhibited the MMF-induced upregulation of CD107a and the lysis of tumor cells through CD56^+ NK cells. Thus, these results are the first to show that MMF augments CD56^+ NK cell lysis of tumor target cells, an effect mediated through NKp46. This novel effect suggests the use of MMF for therapeutic and/or preventive protocols in cancer.展开更多
The main toxicity of organophosphorus pesticides (OPs) is neurotoxicity, which is caused by the inhibition of acetylcholinesterase. OPs also affect immune responses including effects on antibody production, IL-2 pro...The main toxicity of organophosphorus pesticides (OPs) is neurotoxicity, which is caused by the inhibition of acetylcholinesterase. OPs also affect immune responses including effects on antibody production, IL-2 production, T cell proliferation, decreasement of CD5 cells, and increasement of CD26 cells and autoantibodies. However, there have been few papers investigating the mechanism of OP-induced inhibition of cytolytic activity of killer cells. This study reviews the new mechanism of OP-induced inhibition of activities of natural killer (NK), lymphokine-activated killer (LAK) and cytotoxic T lymphocytes (CTL). NK, LAK and CTL induce cell death in tumor or virus-infected target cells by two main mechanisms. The first mechanism is direct release of cytolytic granules that contain perforin, granzymes, and granulysin by exocytosis to kill target cells, which is called the granule exocytosis pathway. The second mechanism is mediated by the Fas ligand (Fas-L)/Fas pathway. To date, it has been reported that OPs inhibit NK, LAK and CTL activities by at least the following three mechanisms: 1) OPs impair the granule exocytosis pathway of NK, LAK and CTL cells by inhibiting the activity of granzymes, and by decreasing the intracellular level of perforin, granzyme A and grannlysin, which was mediated by inducing degranulation of NK cells and by inhibiting the transcript of mRNA of perforin, granzyme A and granulysin; 2) OPs impair the FasL/Fas pathway of NK, LAK and CTL cells, as investigated by using perforin-knockout mice, in which the granule exocytosis pathway of NK cells does not function and only the FasL/Fas pathway remains functional; 3) OPs induce apoptosis of immune cells. Cellular & Molecular Immunology. 2006;3(3):171-178.展开更多
基金supported by grants from the National Natural Science Foundation of China(Nos.32000998,and 32201240)The Young Elite Scientists Sponsorship Program by Henan Association for Science and Technology(No.2022HYTP046)+2 种基金the China Postdoctoral Science Foundation(Nos.2019TQ0285,2019M662513,and 2021TQ0298)Henan provincial Medical Science and Technology Research Project(No.LHGJ20210210)Science and Technology Development Project of Henan Province(Nos.212102310138 and 222102310525).
文摘Chemotherapy remains one of the irreplaceable treatments for cancer therapy.The use of immunogenic cell death(ICD)-inducing chemotherapeutic drugs offers a practical strategy for killing cancer cells,simultaneously eliciting an antitumor immune response by promoting the recruitment of cytotoxic immune cells and production of granzyme B(GrB).However,numerous malignant cancers adaptively acquired the capacity of secreting serpinb9(Sb9),a physiological inhibitor of GrB,which can reversibly inhibit the biological activity of GrB.To circumvent this dilemma,in this study,an integrated tailor-made nanomedicine composed of tumor-targeting peptide(Arg-Gly-Asp,RGD)decorated liposome,doxorubicin(DOX,an effective ICD inducer),and the compound 3034(an inhibitor of Sb9),is developed(termed as D3RL)for breast cancer chemo-immunotherapy.In vitro and in vivo studies show that D3RL can directly kill tumor cells and trigger the host immune response by inducing ICD.Meanwhile,D3RL can competitively relieve the inhibition of Sb9 to GrB.The restored GrB can not only effectively induce tumor immunotherapy,but also degrade matrix components in the tumor microenvironment,consequently improving the infiltration of immune cells and the penetration of nanomedicines,which in return enhance the combined antitumor effect.Taken together,this work develops an integrated therapeutic solution for targeted production and restoration of GrB to achieve a combined chemo-immunotherapy for breast cancer.
基金This work was supported by the National Natural Science Foundation of China (#30630059, #30528007, #30570819, #30571695, #30500467)Ministry of Science & Technology of China (973 Basic Science Project #2003CB515501 #2006CB806504) and Ministry of Education of China (#705029).
文摘Human umbilical cord blood (CB) has recently been used as a source of stem cells in transplantation. NK cells derived from CB are the key effector cells involved in graft-versus-host disease (GVHD) and graft-versus-leukemia (GVL). It was reported that the activity of CB NK cells was lower than that of adult peripheral blood (PB) NK cells. In this study, we analyzed the expression of some NK cell receptors and cytotoxicity-related molecules in CB and PB NK cells. The expressions of activating NK receptors, CD16, NKG2D and NKp46, did not show significant difference between CB and PB NK cells. But the expression of inhibitory receptor NKG2A/CD94 was significantly higher on CB NK cells. As to the effector function molecules, granzyme B was expressed significantly lower in CB NK cells, but the expressions of intracellular perforin, IFN-γ, TNF-α and cell surface FasL and TRAIL did not show difference between CB and PB NK cells. The results indicated that the high expression of NKG2A/CD94 and low expression of granzyme B may be related with the reduced activity of CB NK cells.
文摘Apoptotic cell death plays an important role in the maintenance of the normal physiological state and in the pathogenesis of diseases.Granule exocytosis is the main pathway for the immune elimination of virus-infected cells and tumor cells by cytotoxic T lymphocytes and natural killer cells.In recent study,we have investigated the level of granzyme H in patients with breast cancer and in control subjects using enzymatic method.Our study also included the prediction of different sites of granzyme H that play a role in substrate and inhibitor recognition in apoptosis process by using 3D structural model of the enzyme.The research described the possible post-translational modification sites that may help the enzyme in immune elimination of tumor cells.Our study shows that the level of granzyme H was reduced in patients when compared to normal control subjects.There are a number of amino acids that function as substrate recognition sites in granzyme H.However,inhibitors may inhibit their activity and affect the process of autolysis.
基金the grants 3.0053.92,3.0050.95,9.0038.96,1.5.411.98 from the National Foundation for Scientific Research(FWO)the grants 194.322.1740,195.332.1310,196.322.0140,and OZR.230 from the Research Council of the Free University of Brussels
文摘AIM Several triggering receptors have beendescribed to be involved in natural killer(NK)cell-mediated target cytotoxicity.In these studies,NKcells derived from blood or spleen were used.Pitcells are liver-specific NK cells that possess ahigher level of natural cytotoxicity and a differentmorphology when compared to blood NK cells.The aim of this study was to characterize the roleof the NK-triggering molecules NKR-P1A,ANK61antigen,and CD45 in pit cell-mediated killing oftarget cells.METHODS <sup>51</sup>Cr-release and DNA fragmentationwere used to quantify target cell lysis andapoptosis,respectively.RESULTS Flow cytometric analysis showed thatpit cells expressed CD45,NKR-P1A,and ANK61antigen.Treatment of pit cells with monoclonalantibody(mAb)to CD45(ANK74)not onlyinhibited CC531s or YAC-1 target lysis but alsoapoptosis induced by pit cells.The mAbs to NKR-P1A(3.2.3)and ANK61 antigen(ANK61)had no effect on pit cell-mediated CC531s or YAC-1 targetcytolysis or apoptosis,while they did increase theFcγ receptor positive(FcγR<sup>+</sup>)P815 cytolysis andapoptosis.This enhanced cytotoxicity could beinhibited by 3,4-dichloroisocoumarin,an inhibitorof granzymes.CONCLUSION These results indicate that CD45participates in pit cell-mediated CC531s and YAC-1target cytolysis and apoptosis.NKR-P1A andANK61 antigen on pit cells function as activationstructures against FcγR<sup>+</sup> P815 cells,which wasmediated by the perforin/granzyme pathway.
文摘Despite the introduction of potent immunosuppressive medications within recent decades, acute rejection still accounts for up to 12% of all graft losses, and is generally associated with an increased risk of late graft failure. Current detection of acute rejection relies on frequent monitoring of the serum creatinine followed by a diagnostic renal biopsy. This strategy is flawed since an alteration in the serum creatinine is a late clinical event and significant irreversible histologic damage has often already occurred. Furthermore, biopsies are invasive procedures that carry their own inherent risk. The discovery of non-invasive urinary biomarkers to help diagnose acute rejection has been the subject of a significant amount of investigation. We review the literature on urinary biomarkers here, focusing on specific markers perforin and granzyme B m RNAs, FOXP3 m RNA, CXCL9/CXCL10 and mi RNAs. These and other biomarkers are not yet widely used in clinical settings, but our review of the literature suggests that biomarkers may correlate with biopsy findings and provide an important early indicator of rejection, allowing more rapid treatment and better graft survival.
基金the Foundation of Doctoral Subject in Jinan University(51205069)the Natural Science Foundation of Guangdong,China(5300804)
文摘Objective: To achieve the co-expression of GrB and PFP in Hep-2 cells and analyze the growth inhibiting effects on Hep-2 cells. Methods: Lymphocytes were separated from human laryngeal carcinoma tissue, complete Exon fragments of GrB and PFP were amplified by RT-PCR via extracting lymphocytes total RNA, and they were recombined to the downstream of T7 promoter in the vector pVAX1. The recombinant plasmid pVAX1-PIG was transfected into Hep-2 cells with Lipofectamine 2000. The expression of proteins was identified by RT-PCR, MTT and western blot assay. Results: The gene sequence of the RT-PCR products of GrB and PFP were consistent with the data of GenBank by DNA sequencing analysis. The GrB and PFP cDNA fragment were cloned into the vector of pVAX1 in the right direction and the open reading fragment of GrB and PFP were maintained. The target proteins were detected in the transfected Hep-2 cells, and the inhibitive effect of PFP and GrB on Hep-2 cells growth were studied by thiazolyl blue (MTT) test. Conclusion: The pVAX1-PFP-IRES-GrB plasmid was successfully constructed and expressed, and the expression of PFP and GrB could inhibit the growth of Hep-2 cells.
文摘Vaccines have been shown to cause differential expression of genes and increase antibody titers against antigens. Influenza vaccines may have an effect on unexplained disorders such as Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME). Immunological changes have been identified following immunization with trivalent influenza vaccine (TIV). The objective of this pilot study was to examine the consequences of TIV on cytokine and cytotoxic genes in CFS/ME. Peripheral blood mononuclear cells were preferentially isolated from whole blood of 7 CFS/ME patients and 8 controls. Following total RNA extraction and synthesis of cDNA, reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) was used to determine the expression levels of mRNAs for cytotoxic genes (perforin (PRF1), granzyme A (GZMA), granzyme B (GZMB) and cytokine genes. GZMB was significantly increased overall in the CFS/ME patients compared to the controls. GZMA was significantly increased 28 days after vaccination while PRF1 was reduced prevaccination but increased 14 days post-vaccination in the CFS/ME patients. There were no significant changes in cytokine genes pre or post vaccination. Administration of TIV may increase the expression of lytic genes in CFS/ME and this may contribute to the increase in cytotoxic activity we observed in these patients post vaccination.
文摘Dengue virus (DENV) remains a major public health threat because no vaccine or drugs are available for the prevention and treatment of DENV infection, and the immunopathogenesis mechanisms of DENV infection are not fully understood. Cytotoxic molecules, such as granzyme B (GrzB), may be necessary to control viral infections. However, the exact role of GrzB during DENV infection and the mechanisms regulating GrzB expression during DENV infection are not clear. This study found that miR-27a~, miR-3Oe, and miR-378 were down-regulated in DENV-infected patients, and DENV infection in humans induced a significant up-regulation of GrzB in natural killer (NK) cells and CD8+ T cells. Further investigation indicated that NK cells, but not CD8+ T cells, were the major sources of GrzB, and miR-378, but not miR-27a~ or miR-3Oe, suppressed GrzB expression in NK cells. Notably, we found that overexpression of miR-378 using a miR-378 agomir in DENV-infected mice inhibited GrzB expression and promoted DENV replication. These results suggest the critical importance of miR-378 in the regulation of GrzB expression and a protective role for GrzB in controlling DENV replication in vivo. Therefore, this study provides a new insight into the immunopathogenesis mechanism of DENV infection and a biological basis for the development of new therapeutic strategies to control DENV infection.
文摘Dimethyl fumarate (DMF) is a new drug used to treat multiple sclerosis (MS) patients. Here, we examined the effects of DMF and the DMF metabolite monomethyl fumarate (MMF) on various activities of natural killer (NK) cells. We demonstrated that MMF augments the primary CD56^+, but not CD56^-, NK cell lysis of K562 and RAJI tumor cells. MMF induced NKp46 expression on the surface of CD56^+, but not CD56^-, NK cells after incubation for 24 h. This effect was closely correlated with the upregulation of CD107a expression on the surface of CD56+ NK cells and the induction of Granzyme B release from these cells through this metabolite. An anti-NKp46 antibody inhibited the MMF-induced upregulation of CD107a and the lysis of tumor cells through CD56^+ NK cells. Thus, these results are the first to show that MMF augments CD56^+ NK cell lysis of tumor target cells, an effect mediated through NKp46. This novel effect suggests the use of MMF for therapeutic and/or preventive protocols in cancer.
文摘The main toxicity of organophosphorus pesticides (OPs) is neurotoxicity, which is caused by the inhibition of acetylcholinesterase. OPs also affect immune responses including effects on antibody production, IL-2 production, T cell proliferation, decreasement of CD5 cells, and increasement of CD26 cells and autoantibodies. However, there have been few papers investigating the mechanism of OP-induced inhibition of cytolytic activity of killer cells. This study reviews the new mechanism of OP-induced inhibition of activities of natural killer (NK), lymphokine-activated killer (LAK) and cytotoxic T lymphocytes (CTL). NK, LAK and CTL induce cell death in tumor or virus-infected target cells by two main mechanisms. The first mechanism is direct release of cytolytic granules that contain perforin, granzymes, and granulysin by exocytosis to kill target cells, which is called the granule exocytosis pathway. The second mechanism is mediated by the Fas ligand (Fas-L)/Fas pathway. To date, it has been reported that OPs inhibit NK, LAK and CTL activities by at least the following three mechanisms: 1) OPs impair the granule exocytosis pathway of NK, LAK and CTL cells by inhibiting the activity of granzymes, and by decreasing the intracellular level of perforin, granzyme A and grannlysin, which was mediated by inducing degranulation of NK cells and by inhibiting the transcript of mRNA of perforin, granzyme A and granulysin; 2) OPs impair the FasL/Fas pathway of NK, LAK and CTL cells, as investigated by using perforin-knockout mice, in which the granule exocytosis pathway of NK cells does not function and only the FasL/Fas pathway remains functional; 3) OPs induce apoptosis of immune cells. Cellular & Molecular Immunology. 2006;3(3):171-178.