摘要:

The present study provides evidence that the human natural killer (NK) cell effector mechanism causing target cytolysis has a requirement for L‐arginine. In a deficient medium (DM) containing only salts, buffer system and glucose, NK cell‐mediated cytotoxicity was found to decrease by 70% as compared to that obtained in a complete medium (CM). However, adding L‐arginine to such DM could restore the activity of NK cells to the normal level. Many other components of CM, such as serum, glutamine and vitamins did not improve NK cell‐mediated killing in DM. When all amino acids except L‐arginine were added to DM only a partial recovery of NK cell functional cytolysis was seen. L‐arginine enhanced the NK cell activity in a dose‐dependent manner. Additionally, the inhibitor of both inducible and constitutive nitric oxide synthase, N‐monomethyl‐L‐arginine (L‐NMMA) inhibited NK cytolytic activity in DM supplemented with L‐arginine indicating participation of nitric oxide (NO). The results also show that the stimulatory effect of L‐arginine on human NK cell‐mediated cytotoxicity was accompanied by an increase in NO formation as determined by accumulation of nitrite and citrulline. L‐NMMA gave a dose‐dependent reduction in NO generation as well. The nitrite and citrulline production dose‐dependenlly correlated with not only the concentration of L‐arginine in the cultivation medium, but also the enhanced NK cell‐mediated cytolysis. Taken together, these findings could define a L‐arginine/NO‐linked effector mechanism in human NK cells. Nitrite and citrulline were not formed when NK cell‐mediated target cell killing took place in a L‐arginine‐free DM supplemented with additives. Thus, it appears as if human NK cells may cause target cell killing v

ISSN:0300-9475    

DOI:10.1111/j.1365-3083.1995.tb03687.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The vulnerability of tumour cells to complement‐mediated immune attack is regulated by membrane associated molecules. Recently, we have shown that the expression of the membrane attack complex inhibitor CD59 is enhanced on colonic adenocarcinoma cells compared to normal colonic epithelial cells. CD59 was shown, in the same study, to protect the tumour cells from complement‐mediated lysis. Levamisole (LMS), used in conjunction with 5‐fluorouracil as adjuvant therapy, reduces the incidence of colon cancer relapse following surgical resection. This led to our investigation of the effect of LMS on CD59 expression and function on the human colorectal cell lines HT29 and Caco‐2. When cultured in the presence of 10 μM LMS, the cells reduced their expression of CD59 in a time‐dependent manner. LMS treated HT29 ceils were more sensitive to lysis by complement than control cells, and the reduction in CD59 expression was shown to be partly responsible for this. A reduction in CD59 expression will augment complement‐mediated immune surveillance and may contribute to LMSs anti‐tumour a

ISSN:0300-9475    

DOI:10.1111/j.1365-3083.1995.tb03688.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The ability of B cells to act as effective antigen‐presenting cells is a source of debate which centres on the degree of activation of either B cells or T cells. We have investigated whether B cells treated with interleukin 4 (IL‐4) can express the two signals required to activate T cells: MHC Class 2/antigenic peptide complexes(signal 1) and the costimulatory molecules B7‐1 and B7‐2 (signal 2). We have also determined whether these cells could activate atitigen‐experienced T cellsin vitroand whether they could prime naive T cellsin vivo. We found that B cells expressed abutidant MHC Class 2 molecules and moderate levels of B7‐2 after 24 h culture in IL‐4 with or without purified protein derivative (PPD) but B7‐1 was not detectable. PPD‐pulsed, IL‐4 treated B cells induced antigeti‐experienced T cells to proliferatein vitrobut these cells failed to prime naive T cellsin vivowhen injected itito mice. We conclude that signals, in addition to those mduced with IL‐4, are required for B cells to initiate an immuti

ISSN:0300-9475    

DOI:10.1111/j.1365-3083.1995.tb03689.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

A set of monoclonal antibodies (MoAbs) to leucocyte antigens is an essential tool to identify different cell types and functional membrane molecules involved in immune responses. Since no MoAbs existed to bovine integrins, except against the β2subfamily, we generated MoAbs to β3integrin after the immunization of mice with bovine platelets. Two MoAbs, IL‐A164 (IgG2a) and IL‐A166 (IgG1), were selected that reacted specifically with bovine platelets and detected the same membrane molecule. The antigen was a heterodimer of two polypeptide chains of 122 kDa and 95 kDa as resolved by SDS‐PAGE under reducing conditions. Although the Mr of the smaller subunit is identical to that of β2integrin, pre‐absorption with an antibody to β2(or CD18) did not remove the bovine antigen. Comparing the molecular masses of the two subunits in reduced and non‐reduced forms showed a pattern that was similar to that of human GPIIb/IIIa (also called αIIbβ3or CD41a). Reduction of the bovine molecule increased the apparent Mr of the light chain from 76 kDa to 95 kDa, while the heavy subunit changed from 136 kDa to 122 kDa. As with human GPIIb, the decrease in Mr of the α‐subunit is probably a result of a small disulphide‐linked polypeptide, although no additional evidence for this was detected for the bovine integrin. Sequencing of the N‐terminal amino acids of both bovine polypeptides showed identity of the bovine integrin

ISSN:0300-9475    

DOI:10.1111/j.1365-3083.1995.tb03690.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Sialadenitis develops spontaneously in MRL/Mp mice bearing a lymphoproliferative gene,lpr(MRL/ Mp‐lpr/lpr). Based on recent observations of an oligoclonal expansion of T‐cell receptor (TCR) expressing Vβ chain families (Vβ4, Vβ8.1, 2, Vβ10b) in salivary glands of these mice we have initiated selective antibody therapy. Treatment with monoclonal antibodies (MoAb) specific for T cells expressing a mixture of TCR Vβ4, Vβ8.1, 2 and Vβ10b was applied to MRL/lprmice before and after the spontaneous development of Sialadenitis. Thein vivotreatment with Vβ4, Vβ8.1, 2 and Vβ10b MoAb did not prevent the development of Sialadenitis. However, in animals with established Sialadenitis, treatment with the MoAb significantly decreased the inflammation compared with the control groups, Immuno‐histochemical staining of cell phenotypes demonstrated a change in the ratio of CD4/CD8 in the animals with established Sialadenitis. Altogether, these findings illustrate that it is possible to modulate Sialadenitis and infiltrate cell phenotypesin vivoin MRL/lprmice with specific anti‐TCR

ISSN:0300-9475    

DOI:10.1111/j.1365-3083.1995.tb03691.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The primary structure of the membrane‐bound form of rat immunoglobulin E was determined by PCR amplification and nucleotide sequence analysis of its mRNA. The sequence was found to correspond to the previously identified membrane exons of the rat ɛ chain gene. The donor splice site in the C4 exon was mapped to a position 35 nt upstream of the stop codon for the secreted form of rat IgE. Therefore, the membrane‐bound IgE lacks the 12 C‐terminal amino acids present in the secreted form of the protein. Recently, five novel ɛ chain transcripts were isolated from human IgE producing B‐cells or B‐cell lines. Four of these transcripts encode proteins which differ in their C‐terminal ends from the classical membrane or secreted forms of human IgE. To investigate if these transcripts were likely to represent functional mRNAs, their evolutionary conservation was studied by screening a rat IgE producing B‐cell line for the expression of similar transcripts. By PCR amplification and cloning of transcripts, containing both the C3 and the M2 exons, approximately 10, 000 independent cDNA clones were obtained. These clones were screened with probes directed against regions specifie for each of the five novel human epsilon chain mRNAs. However, no evidence was found for the presence of transcripts with a similar structure, indicating that no specific function associated with these transcripts and their corresponding proteins has been conserved between human and rat. The lack of additional M2‐containing transcripts in the rat suggest that the novel human IgE transcripts are byproducts of differential splicing and that they most likely encode proteins with no evolutionarily i

ISSN:0300-9475    

DOI:10.1111/j.1365-3083.1995.tb03692.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The evolution of cells of the monocyte‐macropbage lineage (MML cells) in the spleen ofLeishmania donovani(LD) infected BALB/c mice was studied. Spleen cells were fractionated on a discontinuous percoll gradient and adherent cells (AC) were purified from fractionated spleen cells by adherence steps that appeared at the interfaces of 25–35%, 35–40%, 40–45% and 45–50% percoll gradients. The AC were characterized as MML cells on the basis of positive staining for non‐specific esterase. Adherent cells that appeared at the interfaces of 25–35% and 40–45% were defined as A and C, respectively, and both of them showed extreme variation in a progressive infection. It was observed that A supported parasite replication whereas C remained refractory when infected with LD in vitro. Furthermore, when A cells and C cells were used as antigen‐presenting cells to stimulate mixed population of IFN‐γ producing and IL‐4 producing T‐cells, it was observed that IL‐4 and IFN‐γ were the predominating cytokine in the T‐cell supernatant, respectively. Both A and C were found to be increased hand‐in‐hand up to 5 months of infection and from then on A decreased and C increased in their numerical strength (A‐C reciprocity). The evolution of A‐C reciprocity coincided with the gradual reduction in the parasitaemia in the spleen suggesting that this may contribute to the

ISSN:0300-9475    

DOI:10.1111/j.1365-3083.1995.tb03693.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Beta 2‐glycoprotein I (β2‐GPI) is a 50 kDa protein in human plasma composed of five repeating complement control protein modules thereby closely resembling complement factor H which has 20 such units. Both β2‐GPI and factor H (150 kDa) have binding sites for negatively charged polyions. β2‐GPI has been shown to act as a cofactor for antiphospholipid antibodies upon their binding to anionic phospholipids. In factor H the polyanion recognition site participates in the discrimination between alternative pathway activating and non‐activating surfaces. In light of the structural similarity between β2‐GPI and factor H we have examined whether β2‐GPI has a role in the alternative complement pathway recognition process. Both activators (zymosan) and non‐activators (sheep erythrocytes) of the alternative complement pathway were coated with C3b. Radiolabelled factor H was observed to recognize C3b on both surfaces, whereas β2‐GPI bound to neither. In competition experiments β2‐GPI could not prevent the association of125I‐H with either non‐activator or activator bound C3b. Conversely, factor H could not replace β2‐GPI as a cofactor for antiphospholipid antibodies upon their binding to anionic phospholipids. It is concluded that β2‐GPI and factor H, despite similarities in structure, exhibit

ISSN:0300-9475    

DOI:10.1111/j.1365-3083.1995.tb03694.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The S‐100 Ca2+binding protein, calprotectin, isolated from neutrophil lysates, has been reported to exhibit zinc reversible biostatic activityin vitro. We verified these findings withC. albicansand investigated whether the growth inhibition resulted from zinc deprivation due to chelation by calprotectin. Calprotectin concentrations of 250 μg/ml significantly inhibited the growth ofC. albicans. This was reversed by supplementing culture medium with 10 μM ZnSO4. Incubation of calprotectin in culture medium for 24 h prior to inoculation significantly reduced the minimum inhibitory concentration. When this latter medium was ultrafiltered to remove the calprotectin and then inoculated withC. albicans, significant growth inhibition was still present: again it was reversed by zinc. These findings implicate zinc chelation as a novel, potentially important host defence function of an abundant neutrophil prot

ISSN:0300-9475    

DOI:10.1111/j.1365-3083.1995.tb03695.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The transforming protein E7 of human papilloma virus type 16 can stimulate cytotoxic T lymphocytes (CTL) which can protect experimental animals against growth of E7 expressing tumour cells. In this study we compared CTL responses in mice immunized with either E7 protein in MF59 adjuvant or with recombinant vaccinia virus expressing E7 (Vac‐E7). We have chosen H‐2dmice because no E7‐specific CTL responses have been described in this MHC haplotype. Immunization of these mice with Vac‐E7 generated CTL which lysed target cells infected with Vac‐E7 or transfected with the E7 gene. CTL from mice immunized with E7 protein in MF59 adjuvant showed specificity for the same target cells. Antibody blocking experiments revealed that both immunization with Vac‐E7 and E7 protein stimulated CD8+effector CTL. The find specificity of CTL induced by the two immunization protocols was similar. A major CTL epitope was mapped to the carboxyl terminal amino acids 48–98 of the E7 protein. Peptide isolation from E7 expressing cells followed by HPLC separation indicated that CTL induced by immunization with protein and Vac‐E7 recognized the same HPLC purified peptide fractions. Together, the study suggests that vaccines based on protein can activate CTL with similar fine specificity to CTL induced by vaccines based on recombinant

ISSN:0300-9475    

DOI:10.1111/j.1365-3083.1995.tb03696.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY