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1.
NK cells are non-T, non-B lymphocytes that kill target cells without previous activation. The immunophenotype and function of these cells in humans and mice are well defined, but canine NK cells remain incompletely characterized. Our objectives were to isolate and culture canine peripheral blood NK cells, and to define their immunophenotype and killing capability. PBMC were obtained from healthy dogs and T cells were depleted by immunomagnetic separation. The residual cells were cultured in media supplemented with IL-2, IL-15 or both, or with mouse embryonic liver (EL) feeder cells. Non-T, non-B lymphocytes survived and expanded in these cultures. IL-2 was necessary and sufficient for survival; the addition of IL-15 was necessary for expansion, but IL-15 alone did not support survival. Culture with EL cells and IL-2 also fostered survival and expansion. The non-T, non-B lymphocytes uniformly expressed CD45, MHC I, and showed significant cytotoxic activity against CTAC targets. Expression of MHC II, CD11/18 was restricted to subsets of these cells. The data show that cells meeting the criteria for NK cells in other species, i.e., non-T, non-B lymphocytes with cytotoxic activity, can be expanded from canine PBMC by T-cell depletion and culture with cytokines or feeder cells.  相似文献   

2.
Natural killer (NK) cells play a role in innate antiviral immunity by directly lysing virus-infected cells and producing antiviral cytokines such as interferon gamma (IFN-γ). We developed a system for characterizing the bovine NK response to foot-and-mouth disease virus (FMDV), which causes a disease of cloven-hoofed animals and remains a threat to livestock industries throughout the world. IL-2 stimulation of PBMC resulted in poor killing of human K562 cells, which are often used as NK target cells, while lysis of the bovine BL3.1 cell line was readily detected. Depletion of NKp46-expressing cells revealed that 80% of the killing induced by IL-2 could be attributed to NKp46+ cells. In order to characterize the response of NK cells against FMDV in vivo, we infected groups of cattle with three different strains of the virus (A24 Cruzeiro, O1 Manisa, O Hong Kong) and evaluated the cytolytic ability of NK cells through the course of infection. We consistently observed a transient increase in cytolysis, although there was variation in magnitude and kinetics. This increase in cytolysis remained when CD3+ cells were removed from the preparation of lymphocytes, indicating that cytolysis was independent of MHC-T cell receptor interaction or γδ T cell activation. In contrast, animals monitored following vaccination against FMDV did not exhibit any increase in NK killing. These data suggest that NK cells play a role in the host immune response of cattle against FMDV, and contrast with the suppression of NK activity previously observed in swine infected with FMDV.  相似文献   

3.
Cytotoxicity of bovine lymphocytes after treatment with lymphokines   总被引：2，自引：0，他引：2  
Cytotoxic lymphocytes were generated from bovine peripheral blood mononuclear leukocytes after in vitro stimulation with lymphokines that contained interleukin-2. Lymphokine-stimulated cultures were cytotoxic to K562 cells (human natural killer [NK] targets) and YAC-1 cells (mouse NK targets), but not to HSB-2 cells (human NK targets) in a 4-hour, 51Cr-release assay. Cells generated after lymphokine activation also mediated antibody-dependent cellular cytotoxicity to HSB-2 cells. Appearance of effector cells as a function of time in culture, method of stimulation, and cold target competition experiments strongly indicated that direct cytotoxicity and antibody-dependent cellular cytotoxicity may have been mediated by the same cell. Cells generated by similar conditions were able to mediate cytotoxicity against infectious bovine rhinotracheitis virus-infected target cells, especially in an 18-hour assay.  相似文献   

4.
Natural killer (NK) cells are one of the main cellular components of the innate immune system. They play an important role in the immune response against infections as well as tumour cells and therefore have two major properties: production of immune regulatory cytokines and chemokines as well as cytolytic destruction of particular target cells. The existence of NK cells in swine is well known as well as the phenotype of resting NK cells, but their response following activation by cytokines is still poorly understood. Therefore, we tested the influence of the immune regulatory cytokines IL-2, IL-12 and IL-18 on cytolytic activity, phenotype, IFN-gamma production and the accumulation of perforin in cytoplasm of peripheral blood mononuclear cells (PBMC) as well as purified NK cells. NK cells were enriched from PBMC using a magnetic cell separation (MACS) strategy with monoclonal antibodies against CD3, CD21 and SWC3, thereby removing T-, B- and myeloid cells. Respective fractions were used in flow cytometry (FCM) based cytolytic assays with the human tumour cell line K562 as target. After stimulation with the cytokines described above, the NK cell enriched CD3(-)CD21(-)SWC3(-) fraction showed an evident increase in the cytolytic activity compared to PBMC. This enhanced cytolytic activity was accompanied by a strong enrichment of IFN-gamma producing cells when a combination of all three cytokines (IL-2/IL-12/IL-18) was used; as determined in ELISPOT assays and intracellular staining of IFN-gamma in FCM. Also, the combination of these three cytokines led to an accumulation of perforin in the cytoplasm and an up-regulation of CD25 compared to control cultures incubated in medium without cytokines. The experiments performed clearly indicate a stimulatory role and strong synergistic effects of the investigated cytokines in the activation of porcine NK cells in vitro, inducing IFN-gamma, perforin production and cytotoxicity against target cells.  相似文献   

5.
Allogeneic PM/86 melanoma cells of Munich Troll miniature swine have been used for the demonstration of porcine peripheral blood NK cell activity. Compared with the specific lysis of xenogeneic K562-, U937- and Vero-target cells, NK cell-mediated cytotoxicity (NK-CMC) against PM/86 melanoma tumor cells was significantly lower in a 16 h chromium release assay. The target cell susceptibility to peripheral blood NK-CMC of both adult Troll miniature swine and German Landrace sows was very similar. Cold target inhibition assays revealed the allogeneic PM/86 melanoma cells to be the most powerful inhibitors of NK-CMC. Nylon wool non-adherent lymphocytes produced interferon (IFN)-alpha in different quantities upon contact with NK susceptible target cells. The NK effector cells could be stimulated to a higher lytic activity against all susceptible targets by a moderate dose of natural human interleukin-2 (nhuIL-2). The role of NK-CMC in melanoma tumor rejection and/or prevention of metastases is yet unknown in swine although porcine melanoma serves as a good model for the disease in man.  相似文献   

6.
The replication of porcine reproductive and respiratory syndrome virus (PRRSV) in lungs and lymphoid tissues of PRRSV-infected pigs is already strongly reduced before the appearance of neutralizing antibodies, indicating that other immune mechanisms are involved in eliminating PRRSV at those sites. This study aimed to determine whether PRRSV Lelystad virus (LV)-specific cytotoxic T-lymphocytes (CTL) can efficiently eliminate PRRSV-infected alveolar macrophages. Therefore, CTL assays were performed with PRRSV-infected alveolar macrophages as target cells and autologous peripheral blood mononuclear cells (PBMC) from PRRSV-infected pigs as a source of PRRSV-specific CTL. PBMC of 3 PRRSV-infected pigs were used either directly in CTL assays, or following restimulation in vitro. CTL assays with pseudorabies virus (PRV) Begonia-infected alveolar macrophages and autologous PBMC, from 2 PRV Begonia-inoculated pigs, were performed for validation of the assays. In freshly isolated PBMC, derived from PRRSV-infected pigs, CTL activity towards PRRSV-infected macrophages was not detected until the end of the experiment (56 days post infection – dpi). Restimulating the PBMC with PRRSV in vitro resulted in proliferation of CD3+CD8high cells starting from 14 dpi. Although CD3+CD8high cells are generally considered to be CTL, CTL activity was not detected in PRRSV-restimulated PBMC of the 3 pigs until 49 dpi. A weak PRRSV-specific CTL activity was observed only at 56 dpi in PRRSV-restimulated PBMC of one pig. In contrast, a clear CTL activity was observed in PRV Begonia-restimulated PBMC, derived from PRV Begonia-infected pigs, starting from 21 dpi. This study indicates that PBMC of PRRSV-infected pigs contain proliferating CD3+CD8high cells upon restimulation in vitro, but these PBMC fail to exert CTL activity towards PRRSV-infected alveolar macrophages.  相似文献   

7.
This study evaluated the early modulation of the phenotype and cytokine secretion in swine immune cells treated with an engineered killer peptide (KP) based on an anti-idiotypic antibody functionally mimicking a yeast killer toxin. The influence of KP on specific immunity was investigated using porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) as ex vivo antigens. Peripheral blood mononuclear cells (PBMC) from healthy pigs were stimulated with KP and with a scramble peptide for 20 min, 1, 4 and 20 h or kept unstimulated. The cells were analyzed using flow cytometry and ELISA. The same time-periods were used for KP pre-incubation/co-incubation to determine the effect on virus-recalled interferon-gamma (IFN-γ) secreting cell (SC) frequencies and single cell IFN-γ productivity using ELISPOT.KP induced an early dose-dependent shift to pro-inflammatory CD172α+CD14+high monocytes and an increase of CD3+CD16+ natural killer (NK) T cells. KP triggered CD8α and CD8β expression on classical CD4−CD8αβ+ cytotoxic T lymphocytes (CTL) and double positive (DP) CD4+CD8α+ Th memory cells (CD4+CD8α+low CD8β+low). A fraction of DP cells also expressed high levels of CD8α. The two identified DP CD4+CD8α+high CD8β+low/+high CTL subsets were associated with tumor necrosis factor alpha (TNF-α) and IFN-γ secretion. KP markedly boosted the reactivity and cross-reactivity of PRRSV type-1- and PCV2b-specific IFN-γ SC. The results indicate the efficacy of KP in stimulating Th1-biased immunomodulation and support studies of KP as an immunomodulator or vaccine adjuvant.  相似文献   

8.
The present study examined the properties of NK activity in Yorkshire swine. The results support other porcine studies which indicate the swine NK system has both similarities and differences to this system in other species. Profiles of NK activity indicated swine NK cells are highly reactive against the YAC-1 lymphoma, the K-562 myeloid leukemia, the P-815 mastocytoma, and the TU-5 virally transformed fibroblast. In contrast, the MOLT-4 and SB leukemias are NK resistant. Kinetic studies indicated that in Yorkshire swine, NK lysis begins 6 h after mixing effectors and targets. The kinetics of the lytic reaction differ both from other breeds of swine and from other species, where cytotoxicity is readily measured in 4-h assays. The delayed lysis was not due to delayed target cell recognition, because Yorkshire swine NK cells are rapidly bound to tumor targets. The delayed lysis seems to be due to a refractoriness in the NK lytic mechanism. This delay may relate to the morphologic finding that the target-binding cell in Yorkshire swine appeared quite different from the large granular lymphocyte (LGL) reported as the NK effector in humans and rodents. Indeed, in light microscopic studies the typical tumor-binding cell in Yorkshire swine is a small, apparently nongranular, lymphocyte. Analysis of NK activity at the single cell level was performed with single effector-tumor conjugates immobilized in agarose. Generally, lysis by target binders paralleled sensitivity to lysis in 51Cr release tests, indicating lysis in agarose may be used as an NK index in swine. Like other species, swine NK cells were found to be nonadherent lymphocytes with a characteristic tissue distribution. Peripheral blood and spleen had the highest levels of NK activity. Lymph node cells displayed a small amount of NK activity which was limited to the YAC-1 target, while thymocytes showed no appreciable NK activity against any of the cell lines tested.  相似文献   

9.
Cytotoxic T lymphocytes (CTL) are associated with virus control in horses infected with equine infectious anemia virus (EIAV). Early in infection, control of the initial viremia coincides with the appearance of CTL and occurs before the appearance of neutralizing antibody. In carrier horses, treatment with immunosuppressive drugs results in viremia before a change in serum neutralizing antibody occurs. Clearance of initial viremia caused by other lentiviruses, including human immunodeficiency virus-1 and simian immunodeficiency virus, is also associated with CTL and not neutralizing antibody. In addition, depletion of CD8+ cells prior to infection of rhesus monkeys with simian immunodeficiency prevents clearance of virus and the same treatment of persistently infected monkeys results in viremia. Cats given adoptive transfers of lymphocytes from vaccinated cats were protected and the protection was MHC-restricted, occurred in the absence of antiviral humoral immunity, and correlated with the transfer of cells with feline immunodeficiency virus-specific CTL and T-helper lymphocyte activities. Therefore, a lentiviral vaccine, including one for EIAV, needs to induce CTL. Based on initial failures to induce CTL to EIAV proteins by any means other than infection, we attempted to define an experimental system for the evaluation of methods for CTL induction. CTL epitopes restricted by the ELA-A1 haplotype were identified and the MHC class I molecule presenting these peptides was identified. This was done by expressing individual MHC class I molecules from cDNA clones in target cells. The target cells were then pulsed with peptides and used with effector CTL stimulated with the same peptides. In a preliminary experiment, immunization of three ELA-A1 haplotype horses with an Env peptide restricted by this haplotype resulted in CTL in peripheral blood mononuclear cells (PBMC) which recognized the Env peptide and virus-infected cells, but the CTL response was transient. Nevertheless there was significant protection against clinical disease following EIAV challenge of these immunized horses when compared with three control horses given the same virus challenge. These data indicated that responses to peptides in immunized horses needed to be enhanced. Optimal CTL responses require help from CD4+ T lymphocytes, and experiments were done to identify EIAV peptides which stimulated CD4+ T lymphocytes in PBMC from infected horses with different MHC class II types. Two broadly cross-reactive Gag peptides were identified which stimulated only an interferon gamma response by CD4+ T lymphocytes, which indicated a T helper 1 response is needed for CTL stimulation. Such peptides should facilitate CTL responses; however, other problems in inducing protection against lentiviruses remain, the most significant of them being EIAV variants that can escape both CTL and neutralizing antibody. A possible solution to CTL escape variants is the induction of high-avidity CTL to multiple EIAV epitopes.  相似文献   

10.
Lectins are relevant tools to isolate and characterize different cellular sub-populations. In this work, we used the lectins Arachis hypogaea (Peanut agglutinin, PNA) and Amaranthus leucocarpus (ALL), specific for Galss1, 3GalNAc, to characterize naive and memory lymphocytes from pigs, experimentally infected with the porcine rubulavirus (RvP). Our results showed that both lectins recognized preferentially lymphocytes with the CD4(+)CD8(+) phenotype (P<0.05). The phenotypic analysis of the cells recognized by these lectins indicated that PNA(+) lymphocytes showed higher rate of the CD29 antigen (PNA(+)CD29(high)) than ALL(+) (ALL(+)CD29(low)). The number of PNA(+)CD29(high) lymphocytes increased after 8 weeks of experimental infection with RvP, and most of the ALL(+)CD29(low) cells became CD29(middle). PNA(+) lymphocytes isolated from infected pigs proliferated after stimulation with the RvP, whereas ALL(+) cells did not. In vitro assays indicated that the ALL(+) cells from previously infected pigs diminished from 7.5 +/- 2 to 0.5 +/- 0.3% after RvP stimulation; whereas PNA(+) cells increased from 4 +/- 1 to 42 +/- 2%, whereas no modification in ALL(+) or PNA(+) cellular population was identified in lymphocytes from naive animals after RvP stimulation. Our results suggest that the cellular distribution/organization of the O-glycosydically linked glycans on lymphocytes may correlate with biological functions, and that PNA could be a tool to isolate specifically porcine memory T cell subsets, whereas ALL could be useful to isolate naive/quiescent T lymphocytes.  相似文献   

11.
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12.
Although CTL are important for control of lentiviruses, including equine infectious anemia virus (EIAV), it is not known if CTL can limit lentiviral replication in the absence of CD4 help and neutralizing antibody. Adoptive transfer of EIAV-specific CTL clones into severe combined immunodeficient (SCID) foals could resolve this issue, but it is not known whether exogenous IL-2 administration is sufficient to support the engraftment and proliferation of CTL clones infused into immunodeficient horses. To address this question we adoptively transferred EIAV Rev-specific CTL clones into four EIAV-challenged SCID foals, concurrent with low-dose aldesleukin (180,000U/m2), a modified recombinant human IL-2 (rhuIL-2) product. The dose was calculated based on the specific activity on equine PBMC in vitro, and resulted in plasma concentrations considered sufficient to saturate high affinity IL-2 receptors in humans. Despite specific activity on equine PBMC that was equivalent to recombinant equine IL-2 and another form of rhuIL-2, aldesleukin did not support the engraftment and expansion of infused CTL clones, and control of viral load and clinical disease did not occur. It was concluded that survival of Rev-specific CTL clones infused into EIAV-challenged SCID foals was not enhanced by aldesleukin at the doses used in this study, and that in vitro specific activity did not correlate with in vivo efficacy. Successful adoptive immunotherapy with CTL clones in immunodeficient horses will likely require higher doses of rhuIL-2, co-infusion of CD4+ T lymphocytes, or administration of equine IL-2.  相似文献   

13.
用从健康猪胸腺提取的 Ｔ 淋巴细胞作抗原免疫 Ｂ Ａ Ｌ Ｂ／ｃ 小鼠。取免疫鼠脾细胞与 Ｓ Ｐ２／０ 骨髓瘤细胞融合，经 ３ 次克隆，共获得 １０ 株稳定分泌抗体的杂交瘤细胞。以细胞反应特异性试验、 Ｗ ｅｓｔｅｒｎｂｌｏｔｔｉｎｇ 分析、流式细胞计数（ Ｆ Ｃ Ｍ ）等方法，确定了对猪 Ｔ 细胞表面抗原特异性反应的单抗（ Ｍ ｃ Ａｂｓ），其中 ２ Ｄ９ 、３ Ｂ１ ０ 可以识别相对分子质量 ５０ ０００ 的 Ｔ 细胞膜蛋白，能标记 ９６％ 的胸腺细胞、８９％ 的外周血 Ｔ 淋巴细胞、８７％ 的脾 Ｔ 淋巴细胞，其特性与猪 Ｃ Ｄ２ 抗原相符；另一株 １ Ｇ１ ２ 可识别相对分子质量 ６３ ０００ 的 Ｔ 细胞膜蛋白，能标记 ９８％ 的胸腺细胞、９１％ 的外周血 Ｔ 淋巴细胞、７８％ 的脾 Ｔ 淋巴细胞，其特性与猪 Ｃ Ｄ５ 抗原相符。  相似文献   

14.
用马立克氏病病毒（MDV）感染5日龄SPF鸡后,取21日龄和35日龄鸡的淋巴细胞,运用3H-TdR掺入法检测T淋巴细胞对ConA和重组鸡白细胞介素18（rChIL-18）的反应,并用MTT法检测NK细胞和CTL对MD肿瘤细胞系CU147的杀伤活性及rChIL-18和IFN-γ对它们的作用。结果显示,SPF鸡感染MDV后淋转水平显著下降,NK细胞、CTL杀伤活性在感染后21日龄时升高,而在35日龄时NK细胞杀伤活性显著下降。rChIL-18对对照组和感染组SPF鸡的淋转水平和杀伤活性均有提高作用,同样IFN-γ也具有提高NK细胞和CTL杀伤活性的作用。  相似文献   

15.
To date cellular immune responses against parvovirus B19 (B19) have not been studied extensively. The aim of this study was to examine the T-cell response against the VP1-unique region as the immunodominant part of the viral structural protein VP1 in individuals with different courses of B19 infection. Therefore, a group of 13 parvovirus-positive probands was separated into subgroups characterized for recent or acute, past or persistent infection by means of the presence of specific immunoglobulin (Ig)M and IgG isotypes and of viral DNA in blood and tissue. Transiently transfected B-cells expressing VP1-unique region were used in ELISpot assays to investigate T-cell responses directed against the VP1-unique region in peripheral blood mononuclear cells (PBMC) of individual donors. Significant numbers of interferon-gamma (IFN-gamma) secreting lymphocytes were detectable in PBMC of all individuals with recent, acute or persistent B19 infection, but not in PBMC of donors with past B19 infection and seronegative individuals. A more detailed analysis of IFN-gamma producing cells by intracellular cytokine staining by flow cytometry revealed, that CD4(+) T cells but not CD8(+) cytotoxic lymphocytes (CTL) were the major subpopulation of IFN-gamma producing cells. These data strongly suggest the need of virus protein production for the maintenance of VP1-unique region-specific CD4(+) T-helper cell responses in B19-infected individuals.  相似文献   

16.
Neutral glycosphingolipids (GSLs) are considered activation markers on human lymphocytes, which are fundamental for studying the immune system. For cattle, only a limited number of activation markers has yet been identified. We recently showed that Shiga toxin 1, known to use globotriaosylceramide (Gb(3) syn. CD77) as a cellular receptor, depresses proliferation of activated bovine lymphocytes [Infect. Immunol. 67 (1999b) 2209]. In order to confirm the expression of Gb(3)/CD77 on bovine lymphocytes, we flowcytometrically examined a bovine B-lymphoma cell line (BL-3) and bovine peripheral blood mononuclear cells (PBMC) before and after mitogenic stimulation and biochemically characterized neutral GSLs extracted from PBMC. CD77 was detected on the surface of BL-3 cells and cultured PBMC essentially after mitogenic stimulation. Although expressed by all PBMC subpopulations identified, the portion of CD7+ cells was highest for BoCD8+ cells, followed by B-cells and BoCD4+ cells at day 4 of cultivation. Ceramide trihexoside of stimulated PBMC was structurally determined as Gal(alpha1-4)Gal(1-4)Glc(1-1)ceramide (Gb(3)). Biochemically, Gb(3) was also detected within unstimulated PBMC which contained ceramide monohexoside (CMH) and Gb(3) in a ratio of about 4:1. However, stimulation induced an increase of CMH and Gb(3) by a factor of 2.5 and 10, respectively, implicating that bovine lymphocytes regulate surface expression of Gb(3)/CD77 predominantly by quantitative changes in the Gb(3) metabolism. This report presents Gb(3)/CD77 as the first GSL identified on bovine immune cells and highly recommends this activation dependent antigen as a useful tool to investigate lymphocyte activation within the bovine immune system.  相似文献   

17.
In this study we have used the expression of perforin to characterize subsets of porcine cytotoxic lymphocytes. Perforin positive lymphocytes expressed both CD2 and CD8, most were small dense lymphocytes (SDL) and up to 90% were CD3 negative. However, the numbers of perforin positive T-cells increased with the age of the animal and their populations increased after specific antigen stimulation in vitro. The remaining perforin positive lymphocytes were large and granular and contained more CD3+CD5+CD6+ T-cells (−40%) of which a substantial proportion also co-expressed CD4. Perforin was expressed in subpopulations of both CD8 and CD8β lymphocytes, but was not expressed in γδ T-cells or monocyte/macrophages. The perforin positive CD3− subset was phenotypically homogeneous and defined as CD5−CD6−CD8β−CD16+CD11b+. This population had NK activity and expressed mRNA for the NK receptor NKG2D, and adaptors DAP10 and DAP12. Perforin positive T-cells (CD3+) could be divided into at least three subsets. The first subset was CD4−CD5+CD6+CD11b−CD16− most were small dense lymphocytes with cytotoxic T-cell activity but not all expressed CD8β. The second subset was mainly observed in the large granular lymphocytes. Their phenotype was CD4+CD5+CD6+CD8β+CD16−CD11b− and also showed functional CTL activity. Thus not all of double positive T-cells are memory helper T-cells. The third subset did not express the T-cell co-receptor CD6, but up to half of them expressed another T-cell co-receptor CD5. The majority of this subset expressed CD11b and CD16, thus the third perforin positive T-cell subset was CD3+CD4−CD5+CD6−CD8β±CD11b+CD16+, and possessed MHC-unrestricted cytotoxicity and LAK activity.  相似文献   

18.
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19.
Cytotoxic T lymphocytes are involved in controlling intracellular pathogens in many species, including horses. Particularly, CTL are critical for the control of equine infectious anemia virus (EIAV), a lentivirus that infects horses world-wide. In humans and animal models, CTL clones are valuable for evaluating the fine specificity of epitope recognition, and for adoptive immunotherapy against infectious and neoplastic diseases. Cloned CTL would be equally useful for similar studies in the horse. Here we present the first analysis of a method to generate equine CTL clones. Peripheral blood mononuclear cells were obtained from an EIAV-infected horse and stimulated with the EIAV Rev-QW11 peptide. Sorted CD8+ T cells were cloned by limiting dilution, and expanded without further antigen addition using irradiated PBMC, anti-equine CD3, and human recombinant IL-2. Clones could be frozen and thawed without detrimental effects, and could be subsequently expanded to numbers exceeding 2 x 10(9)cells. Flow cytometry of expanded clones confirmed the CD3+/CD8+ phenotype, and chromium release assays confirmed CTL activity. Finally, sequencing TCR beta chain genes confirmed clonality. Our results provide a reliable means to generate large numbers of epitope-specific equine CTL clones that are suitable for use in downstream applications, including functional assays and adoptive transfer studies.  相似文献   

20.
The morphologic and biological properties of porcine cells mediating natural killer (NK) activity were determined. In a previous study, we demonstrated that lymphocytes from the peripheral blood of pigs greater than 1 week of age possessed NK activity to K562 tumor cells and that lymphocytes from the blood and spleen of pigs greater than 1 day of age were able to mediate natural cytotoxicity against parainfluenza-3 (PI3) virus-infected Vero cells (Yang and Schultz, 1986a). Discontinuous density gradients were used to enrich NK cells. NK cytotoxicity was mainly present in high-density Percoll fractions (50 to 55% and 55 to 60%); little or no NK activity was present in lower density fractions. The NK cell enriched lymphocytes responded to the mitogens PHA, ConA and PWM. NK cells were sensitive to the suppressive effect of corticosteroid, but Protein A did not affect NK activity. The amount of cytotoxicity directly corresponded to the degree of binding that occurred between the NK enriched lymphocyte population and the target cells. Cytochemical and morphological studies demonstrated that these bond cells which are believed to be responsible for the NK activities, were mainly small to medium lymphocytes lacking azurophilic cytoplasmic granules. These findings were confirmed by ultrastructural studies of effector and "target-binding" cells. The results of the present study suggested that the cells mediating NK activity in pigs have the morphological and density characteristics of small and medium sized lymphocytes; findings that differ from those described for NK cells in human and other animal species.  相似文献   

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