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At least 199 records · Page 11Linked to original sources
PubMed2000

Long term persistence of herpes simplex virus-specific CD8+ CTL in persons with frequently recurring genital herpes.

Herpes simplex virus (HSV) establishes a lifelong infection in humans. Reactivation of latent virus occurs intermittently so that the immune system is frequently exposed to viral Ag, providing an opportunity to evaluate memory T cells to a persistent human pathogen. We studied the persistence of genital herpes lesion-derived HSV-specific CD8+ CTL from three immunocompetent individuals with frequently recurring genital HSV-2 infection. All CTL clones were HSV-2 type specific and only one to three unique clonotypes were identified from any single biopsy specimen. The TCRBV genes utilized by these clonotypes were sequenced, and clonotype-specific probes were used to longitudinally track these clonotypes in PBMC and genital lesions. CTL clonotypes were consistently detected in PBMC and lesions for at least 2 and up to 7 years, and identical clonotypes infiltrated herpes lesions spaced as long as 7.5 years apart. Moreover, these clones were functionally lytic in vivo over these time periods. Additionally, CTL clones killed target cells infected with autologous viral isolates obtained 6.5 years after CTL clones were established, suggesting that selective pressure by these CTL did not result in the mutation of CTL epitopes. Thus, HSV recurs in the face of persistent CD8+ CTL with no evidence of clonal exhaustion or mutation of CTL epitopes as mechanisms of viral persistence.

Cell Movement↗
PubMed2001

Th1 cytokine-conditioned bone marrow-derived dendritic cells can bypass the requirement for Th functions during the generation of CD8+ CTL.

Bone marrow-derived dendritic cell (BMDC) subsets have distinct immunoregulatory functions. Th1 cytokine-induced BMDC (BMDC1), compared with Th2 cytokine-induced BMDC2, have superior activities for the differentiation and expansion of CTL. To evaluate the cellular interactions between dendritic cells and CD8+ T cells for the induction of CTL, BALB/c-derived BMDC subsets were cocultured with purified CD8+ T cells from C57BL/6 mice. Our results demonstrate that BMDC1 support the generation of allogeneic CD8+ CTL in the absence of CD4+ Th cells. In contrast, BMDC0 (GM-CSF- plus IL-3-induced BMDC) and BMDC2 failed to promote the differentiation of CD8+ CTL. Using Ab-blocking experiments and studies with gene knockout mice, IL-2 and LFA-1 are demonstrated to be critical for BMDC1-induced CTL differentiation. Unexpectedly, BMDC1 were able to induce CTL from CD8+ T cells isolated from IFN-gamma-/- and IFN-gamma receptor-/- mice. However, BMDC1 produced higher levels of IFN-beta than other BMDC subsets, and anti-IFN-beta mAb blocked BMDC1-dependent CTL generation. These results indicated an indispensable role of IFN-beta, but not IFN-gamma, during BMDC1-induced CTL differentiation. We conclude that Th1-cytokine-conditioned BMDC1 can bypass Th cell function for the differentiation of naive CD8+ T cells into CTL.

Animals↗
PubMed2002

Recombinant canarypox vaccine-elicited CTL specific for dominant and subdominant simian immunodeficiency virus epitopes in rhesus monkeys.

Since virus-specific CTL play a central role in containing HIV replication, a candidate AIDS vaccine should generate virus-specific CTL responses. In this study, the ability of a recombinant canarypox virus expressing SIV Gag-Pol-Env (ALVAC/SIV gag-pol-env) was assessed for its ability to elicit both dominant and subdominant epitope-specific CTL responses in rhesus monkeys. Following a series of five immunizations, memory CTL responses specific for a dominant Gag epitope could be demonstrated in the peripheral blood of vaccinated monkeys. Memory CTL responses to a subdominant Pol epitope were undetectable in these animals. Following challenge with SIVmac251, the experimentally vaccinated animals developed high frequency CTL responses specific for the dominant Gag epitope that emerged in temporal association with the early containment of viral replication. Interestingly, the experimentally vaccinated, but not the control vaccinated animals, developed CTL responses to the subdominant Pol epitope that were detectable only after containment of early viremia. Thus, recombinant canarypox vaccination elicited low frequency, but durable memory CTL populations. The temporal association of the emergence of the dominant epitope-specific response with early viral containment following challenge suggests that this immune response played a role in the accelerated clearing of early viremia in these animals. The later emerging CTL response specific for the subdominant epitope may contribute to the control of viral replication in the setting of chronic infection.

Animals↗
PubMed2002

In vivo triggering through 4-1BB enables Th-independent priming of CTL in the presence of an intact CD28 costimulatory pathway.

Triggering of 4-1BB, a member of the TNFR family, through in vivo administration of agonistic anti-4-1BB Ab delivers a powerful costimulatory signal to CTL. We found this signal to effectively replace the need for CD4(+) T cell help in the cross-priming of tumor-specific CTL immunity. Furthermore, 4-1BB Ab can convert an otherwise tolerogenic peptide vaccine into a formulation capable of efficient CTL priming. Initial activation of naive CTL can occur in the absence of 4-1BB costimulation, but this signal permits increased survival of Ag-stimulated CTL. Because naive CTL do not express 4-1BB at their surface, susceptibility to 4-1BB triggering depends on prior up-regulation of this receptor. We show that this requires both stimulation of the TCR and CD28-dependent costimulation. Accordingly, blockade of the CD28-costimulatory pathway abrogates the capacity of agonistic anti-4-1BB Ab to trigger Th-independent CTL immunity. In conclusion, our data reveal that the 4-1BB-mediated survival signal is positioned downstream of Ag-specific TCR triggering and CD28-dependent costimulation of naive CTL. The powerful effects of 4-1BB triggering on the induction, amplification, and persistence of CTL responses provide a novel strategy for increasing the potency of vaccines against cancers.

4-1BB Ligand↗
PubMed2004

Recognition of variant HIV-1 epitopes from diverse viral subtypes by vaccine-induced CTL.

Recognition by CD8(+) T lymphocytes (CTL) of epitopes that are derived from conserved gene products, such as Gag and Pol, is well documented and conceptually supports the development of epitope-based vaccines for use against diverse HIV-1 subtypes. However, many CTL epitopes from highly conserved regions within the HIV-1 genome are highly variable, when assessed by comparison of amino acid sequences. The TCR is somewhat promiscuous with respect to peptide binding, and, as such, CTL can often recognize related epitopes. In these studies, we evaluated CTL recognition of five sets of variant HIV-1 epitopes restricted to HLA-A*0201 and HLA-A*1101 using HLA transgenic mice. We found that numerous different amino acid substitutions can be introduced into epitopes without abrogating their recognition by CTL. Based on our findings, we constructed an algorithm to predict those CTL epitopes capable of inducing responses in the HLA transgenic mice to the greatest numbers of variant epitopes. Similarity of CTL specificity for variant epitopes was demonstrated for humans using PBMC from HIV-1-infected individuals and CTL lines produced in vitro using PBMC from HIV-1-uninfected donors. We believe the ability to predict CTL epitope immunogenicity and recognition patterns of variant epitopes can be useful for designing vaccines against multiple subtypes and circulating recombinant forms of HIV-1.

AIDS Vaccines↗
PubMed2006

A single amino acid difference within the alpha-2 domain of two naturally occurring equine MHC class I molecules alters the recognition of Gag and Rev epitopes by equine infectious anemia virus-specific CTL.

Although CTL are critical for control of lentiviruses, including equine infectious anemia virus, relatively little is known regarding the MHC class I molecules that present important epitopes to equine infectious anemia virus-specific CTL. The equine class I molecule 7-6 is associated with the equine leukocyte Ag (ELA)-A1 haplotype and presents the Env-RW12 and Gag-GW12 CTL epitopes. Some ELA-A1 target cells present both epitopes, whereas others are not recognized by Gag-GW12-specific CTL, suggesting that the ELA-A1 haplotype comprises functionally distinct alleles. The Rev-QW11 CTL epitope is also ELA-A1-restricted, but the molecule that presents Rev-QW11 is unknown. To determine whether functionally distinct class I molecules present ELA-A1-restricted CTL epitopes, we sequenced and expressed MHC class I genes from three ELA-A1 horses. Two horses had the 7-6 allele, which when expressed, presented Env-RW12, Gag-GW12, and Rev-QW11 to CTL. The other horse had a distinct allele, designated 141, encoding a molecule that differed from 7-6 by a single amino acid within the alpha-2 domain. This substitution did not affect recognition of Env-RW12, but resulted in more efficient recognition of Rev-QW11. Significantly, CTL recognition of Gag-GW12 was abrogated, despite Gag-GW12 binding to 141. Molecular modeling suggested that conformational changes in the 141/Gag-GW12 complex led to a loss of TCR recognition. These results confirmed that the ELA-A1 haplotype is comprised of functionally distinct alleles, and demonstrated for the first time that naturally occurring MHC class I molecules that vary by only a single amino acid can result in significantly different patterns of epitope recognition by lentivirus-specific CTL.

Alleles↗
PubMed2006

Differential selection pressure exerted on HIV by CTL targeting identical epitopes but restricted by distinct HLA alleles from the same HLA supertype.

HLA diversity is seen as a major challenge to CTL vaccines against HIV. One current approach focuses on "promiscuous" epitopes, presented by multiple HLA alleles from within the same HLA supertype. However, the effectiveness of such supertype vaccines depends upon the functional equivalence of CTL targeting a particular epitope, irrespective of the restricting HLA. In this study, we describe the promiscuous HIV-specific CTL epitopes presented by alleles within the B7 supertype. Substantial differences were observed in the ability of CTL to select for escape mutation when targeting the same epitope but restricted by different HLA. This observation was common to all six promiscuous B7 epitopes identified. Moreover, with one exception, there were no significant differences in the frequency, magnitude, or immunodominance of the CTL responses restricted by different HLA alleles to explain these discrepancies. This suggests that the unique peptide/MHC complexes generated by even closely related HLA induce CTL responses that are qualitatively different. This hypothesis is supported by additional differences observed between CTL targeting identical epitopes but restricted by different HLA: first, the occurrence of distinct, HLA-specific escape mutation; second, the recruitment of distinct TCR repertoires by particular peptide/MHC complexes; and, third, significant differences in the functional avidity of CTL. Taken together, these data indicate that significant functional differences exist between CTL targeting identical epitopes but restricted by different, albeit closely related HLA. These findings are of relevance to vaccine approaches that seek to exploit HLA supertypes to overcome the problem of HLA diversity.

Alleles↗
PubMed1999

Generation of IL-2-dependent cytolytic T lymphocytes (CTLs) with altered TCR responses derived from antigen-dependent CTL clones.

Ag-specific CD8+ CTL clones require TCR stimulation to respond to IL-2 for growth. Because IL-2 may be produced in the vicinity of CD8+ CTLs when Ag is limiting at the end of an immune response, we have examined the effect of culturing viral-specific CTL clones in IL-2 in the absence of antigenic stimulation. Limiting dilution analysis revealed a high precursor frequency for CTL clones derived from IL-2 propagation (termed CTL-factor dependent (FD)) that are dependent upon exogenous IL-2 for growth and survival and no longer require TCR stimulation to proliferate. Culturing CTL-FDs with infected splenocytes presenting Ag and IL-2 did not revert the clones but did lead to a TCR-induced inhibition of proliferation. The derived CTL-FDs have lost the ability to kill via the perforin/granule exocytosis mechanism of killing, although they express similar levels of TCR, CD3epsilon, CD8alphabeta, CD45, and LFA-1 compared with the parental clones. The CTL-FDs retain Fas ligand/Fas-mediated cytotoxicity, and IFN-gamma production and regulate the expression of CD69 and IL-2Ralpha when triggered through the TCR. A parental CTL protected BALB/c mice from a lethal challenge of influenza virus, whereas a CTL-FD did not. These findings represent a novel regulatory function of IL-2 in vitro that, if functional in vivo, may serve to down-regulate cellular immune responses.

Administration, Intranasal↗
PubMed1999

Human CD28-CD8+ T cells contain greatly expanded functional virus-specific memory CTL clones.

At birth, almost all human peripheral blood CD8+ T cells express the costimulatory molecule CD28. With increasing age, the proportion of CD8+ T cells that lack CD28 increases. Because the Ag specificity of CD28-CD8+ T cells has not previously been defined, we studied the contribution of CD28-CD8+ T cells to the memory CD8+ CTL response against two human persistent viruses, human CMV (HCMV) and HIV. From PBMC of healthy virus carriers we generated multiple independent CTL clones specific for defined viral peptides and sequenced their TCR beta-chains. We designed clonotypic oligonucleotides complementary to each beta-chain hypervariable sequence and quantified the size of individual immunodominant CTL clones in PBMC. Some individual CTL clones were very large, comprising up to 3.1% of all CD8+ T cells in PBMC, and were generally maintained at a stable level for months. Individual virus-specific CTL clones were consistently more abundant in purified CD28- cells than in the CD8+ population as a whole. Because CD28-CD8+ cells as a population have been reported to proliferate poorly in response to mitogen, we studied the function of these virus-specific CD28- CTL clones by quantifying the frequency of peptide-specific CTL precursors using limiting dilution analysis. CD28-CD8+ T cells contained high frequencies of functional memory CTL precursors specific for peptides of HCMV or HIV, generally higher than in the CD8+ T cell population as a whole. We conclude that in asymptomatic HCMV and HIV infection, human CD28-CD8+ T cells contain high frequencies of functional virus-specific memory CTL clones.

Amino Acid Sequence↗
PubMed1999

Augmentation of an antitumor CTL response In vivo by inhibition of suppressor macrophage nitric oxide.

Evidence is provided that inhibition of macrophage NO production can augment in vivo CTL responses. Specifically, administration of NG-monomethyl-l -arginine (NGMMA) via osmotic pumps increases the tumor-specific CTL response against the P815 mastocytoma in the peritoneal cavity of preimmunized mice. Both the magnitude and duration of the CTL response were increased. That the augmented CTL response resulted from inhibition of the NO synthase pathway is supported by the finding that macrophage NO production from NGMMA-treated mice was reduced. Also, in vitro inhibition of NO production by peritoneal exudate cells from P815 tumor-challenged mice augmented the secondary CTL response observed. Cell proliferation was augmented by NGMMA in these cultures, suggesting that macrophage NO may suppress CTL by inhibiting clonal expansion. NO-mediated inhibition was observed in vivo in this experimental system, even though the CTL response is not suppressed, in that tumor rejection occurs. Therefore, the present results are consistent with the conclusion that macrophage NO-mediated inhibition of the CTL response is a side effect of activating macrophages rather than resulting from the action of a distinct subset of what have long been termed suppressor macrophages. Most important, the results indicate that NO-mediated suppressor macrophage activity can be an important CTL immunoregulatory element in vivo.

Animals↗
PubMed1991

Failure of a tumour to prime CTL specific for some of the minor H antigens it expresses but not others.

The H-Y-expressing murine tumour, ET-5, specifically immunizes B6 female mice that have rejected it against H-Y-positive male skin grafts, yet fails to prime their spleen cells for the generation of H-Y-specific cytotoxic T lymphocytes (CTL). ET-5 also fails to prime relevant congenic hosts to generate CTL specific for H-3 or H-25 minor H antigens, or major histocompatibility complex (MHC) class I antigens, all of which are expressed in immunogenic form by ET-5. Nonetheless, C3H.SW mice, which are MHC-compatible with B6 mice in which ET-5 originated, but differ from B6 at many minor H loci, can be primed to generate CTL directed against one or more unidentified minor H antigens. These CTL are conventional MHC-restricted, CD8+ T cells, and require priming in vivo for their generation. Significantly, C3H.SW females can be primed by ET-5 to generate B6-specific CTL, but not H-Y-specific CTL. Thus CTL priming is selective in the sense that ET-5 primes CTL specific for some of the antigens it expresses but not others. The basis for this selectivity is not known but, in the case of H-Y antigen, it appears not to result from an inability of ET-5 to express either H-2Db-encoded antigens, the restriction element for H-Y-specific CTL in B6 females, or H-Y itself in vivo.

Animals↗
PubMed1989

[The rationale and practice of CTL therapy against cancer in the mouse and human].

It is essential to investigate and elucidate the immune response especially T cell response to either syngeneic or autologous tumor for establishing a rational immunotherapy of cancer. We reported that major immune effector cells capable of inducing tumor regression are cytotoxic T lymphocytes (CTL). We found that there are at least two distinct CTL subsets directed to syngeneic tumor. One CTL subset which is selectively induced by syngeneic solid tumor is independent from CD4 positive helper T cells but requires a soluble factor (s) released from macrophage-like accessory cells designated killer T cell activating factor (KAF) in its induction and generation directed to the homologous tumor. The other CTL subset which is usually induced by syngeneic tumor of hematocytic origin is dependent on CD4 positive helper T cells in its induction. On the basis of our findings regarding the induction and activation mechanism of CTL to syngeneic tumors in the mouse, we have investigated the mechanisms of human CTL generation to autochthonous tumor in peripheral blood mononuclear cells of cancer patients. It was found that the nature of human CTL and its generation to autochthonous tumor are similar to those of murine CTL to syngeneic solid tumor. We are now establishing a rational cancer specific immunotherapy utilizing intravenous passive cell transfer of in vitro activated CTL to autochthonous tumor into an original cancer patient.

Animals↗
PubMed1989

In vivo mechanisms of alloreactivity. VI. Evidence that alloantigen deposition initiates both local and systemic mechanisms that influence CTL accumulation at a graft site.

We have used sponge matrix allografts to investigate how alloantigen influences the pattern of CTL accumulation at a graft site. These studies employed two limiting dilution analysis techniques to monitor CTL accumulation. One technique quantitates the subpopulation of CTL that show evidence of in vivo contact with graft alloantigens (alloantigen-conditioned CTL or cCTL). The other quantitates all CTL with specificity for graft alloantigens, regardless of their differentiative status. Using these techniques, we have demonstrated that sponge allografts acquire three types of CTL: (a) donor-reactive CTL precursors (pCTL), (b) donor-reactive cCTL, and (c) pCTL with irrelevant antigen specificity. Sponge isografts rarely acquire LDA-detectable CTL, unless they receive a concurrent allogeneic stimulus at a distant anatomic site. In that instance, sponge isografts acquired pCTL, but not cCTL. This indicates that an ongoing immune response to alloantigens can influence the immunologic characteristics of an unrelated inflammatory response occurring elsewhere. We further observed that sponge isografts can be made to acquire alloreactive cCTL only when specific alloantigens are placed in the isograft. This indicates that specific grant alloantigen present at the graft site plays a necessary but undefined role in the acquisition or development of cCTL in sponge allografts. Collectively, these data demonstrate that alloantigen deposition initiates both local and systemic mechanisms that influence alloreactive CTL accumulation at a graft site.

Animals↗
PubMed1986

The specificity of H-2-restricted cytotoxic T lymphocytes directed to AKR/Gross leukemia virus-induced tumors. III. Coordinate alterations in viral gp70 antigen expression and restoration of CTL-susceptibility to insusceptible variant tumors.

Two variant subclones, called cl.18-5 and cl.18-12, were derived from the AKR.H-2bSL1 tumor cell line that were, in contrast to the parental cells, selectively insusceptible to H-2-restricted anti-AKR/Gross virus cytotoxic T lymphocytes (CTL). Cell surface expression of viral envelope (env) and group-specific antigens (gag) on these CTL-resistant variants were analyzed and compared with the expression of these antigens on AKR.H-2bSL1 and two other CTL-susceptible clones, cl.1 and cl.5, also derived from AKR.H-2bSL1. Although normal levels of gag-encoded and H-2 antigens were displayed on the CTL-resistant variants, the expression of five distinct determinants of viral gp70 antigen as defined by monoclonal antibodies was significantly decreased on these CTL-resistant variants relative to their expression on the CTL-susceptible cell lines. However, similar dramatic changes in cell surface gp70 antigen expression were undetectable as defined by anti-gp70-specific antiserum. Immunoprecipitation and gel electrophoretic analysis revealed that gp70 molecules from cl.18-5 cells had a lower m.w. than those of AKR.H-2bSL1, but there were no differences in the m.w. of gp70 antigens from AKR.H-2bSL1, cl.5, and cl.18-12 cells. Expression of the five gp70 antigenic determinants mentioned above was completely restored by exposure of cl.18-5 and cl.18-12 cells to the halogenated pyrimidine, iododeoxyuridine (IudR). Treatment of cl.18-5 and cl.18-12 cells with IudR simultaneously restored CTL susceptibility of these cells to anti-AKR/Gross virus CTL without affecting gag and H-2 antigen expression. Viral gp70 antigen immunoprecipitated from IudR-treated cl.18-5 cells had a mobility slightly lower, but different from that of untreated cl.18-5 cells. Pulse-labeling with [35S]-methionine showed that IudR treatment of cl.18-5 cells caused the expression of an additional high m.w. gp70 precursor protein originally absent in untreated cl.18-5 cells but present on parental AKR.H-2bSL1 cells. Collectively, these results pointed to the involvement of viral gp70 antigenic determinants in the recognition of AKR/Gross virus-induced tumor targets by anti-AKR/Gross virus CTL.

AKR murine leukemia virus↗
PubMed1985

In vivo priming of mouse CTL precursors directed to product of a newly defined minor H-42 locus is under a novel control of class II MHC gene.

In a previous study, we discovered a new mouse minor histocompatibility antigen encoded by a locus at 8.5 cM apart from the H-2 complex, and we have since named the locus H-42. One allele of H-42, which is named H-42a, had been elucidated, but the other alleles, which we tentatively named H-42b, have not been elucidated. In the present study, we explored MHC control on the anti-H-42a cytotoxic T lymphocyte (CTL) responsiveness in H-42b mice. In vivo immunization (i.v. injection) of H-42b mice with 5 to 30 X 10(6) spleen cells (SC) bearing allogeneic H-42a antigen but carrying H-2 complex (mouse MHC) matched with the H-42b mice failed to prime anti-H-42a CTL but induced stable and specific anti-H-42a CTL unresponsiveness, i.e., tolerance, in the H-42b recipient mice. In contrast, H-2 heterozygous H-42b F1 mice injected with SC bearing H-42a alloantigen on either of the parental H-2 haplotypes were effectively primed to generate anti-H-42a CTL. Exploration of the region or subregion in the H-2 complex of H-42a donor SC that should be compatible with H-42b recipient mice for the induction of their anti-H-42a CTL tolerance demonstrated that the compatibility at I region, most probably I-A subregion, but not at K, S, or D region, determined the induction of the tolerance. MHC class II compatible H-42a skin graft (SG) to H-42b mice, however, consistently primed the anti-H-42a CTL in the H-42b recipients. These results were discussed in several aspects, including uniqueness of MHC class II control on the CTL response to minor H-42a antigen, possibility of inactivation of responding anti-H-42a precursor CTL or helper T cells in H-42b mice by encountering the veto cells present in MHC class II-matched H-42a SC population, and significance of the present observations as a mechanism of CTL tolerance to self-components.

Animals↗
PubMed1983

Two distinct suppressor T cells acting in concert cause suppression of cytolytic T lymphocyte (CTL) response to hapten-altered self in vivo.

The participation of two subpopulations of suppressor T cells (Ts) active in the suppression of hapten-specific contact sensitivity (CS) was investigated in the down-regulation of in vivo development of CTL to hapten-altered self. We have shown that Ts efferent (Ts-eff) cell that is induced by tolerizing mice with an i.v. injection of hapten-coupled syngeneic spleen cells, and the auxiliary Ts cell (Ts-aux), which is generated by dermal application of hapten, together suppress the generation of CTL. Thus, when tolerant mice possessing Ts-eff cells were concomitantly sensitized for CTL and CS (which causes the arisal of Ts-aux and TDTH effector cells), the development of CTL was suppressed. Furthermore, adoptive transfer of lymph node cells from dermally sensitized mice into tolerant mice also suppressed the CTL response. Use of lymph node cells from mice pretreated with cyclophosphamide before dermal sensitization and therefore lacking Ts-aux cells was not efficient in suppressing the CTL response. Thus, neither Ts-eff alone nor TDTH in conjunction with Ts-aux were capable of suppressing the development of CTL. In addition to supporting the view that the in vivo generation of CTL is suppressed when both Ts-eff and Ts-aux cells are present, the data indicate that suppressor cells operational for one T cell-mediated response (CS) are equally functional for a separate unrelated one (CTL).

Animals↗
PubMed1982

Identification of human CML target. HLA-B locus (B12) antigen variants defined by CTL generated between B locus-identical (B12) responder-stimulator pairs.

The genetics of human CML targets were studied by seven CTL generated in combinations iun which the responder/stimulator difference was limited to one (or two) HLA-A, -B, or -C antigens. Unstimulated peripheral blood lymphocytes were used as targets. CTL sensitized against antigens A11, Aw31, or B17 lysed all cells bearing the respective target from a large panel of cells from unrelated individuals. Hence, at least one CTL clone was directed against the HLA antigen molecule. However, all CTL also exerted cross-kill to cells not sharing the stimulating HLA antigen. For two CTL, the target of the cross-kill was not clarified. Five CTL were found where the cross-kill was directed against antigen HLA-B12 (Bw44 and Bw45). All these cTL were generated in R/S pairs identical for B locus antigens (Bw44/Bw35 heterozygotes). The individual CTL lysed different parts of the panel of B12-positive target cells. The interpretation is that these CTL detect subtypes of HLA antigens, but alternative possibilities are also considered. Four B12 subtypes are described, tentatively designated as B12-related CML targets. Identification of HLA-B-related CML targets represent CML "typing" of HLA-antigen differences that were not detected serologically. The subtypes can now be tested for their possible functional significance.

B-Lymphocytes↗
PubMed1995

Activated adhesion of CTL to MHC class I but not to fibronectin is inhibited by cis unsaturated fatty acids and phenylarsine oxide.

Binding of CTL to MHC class I or fibronectin is activated through TCR signaling. Once activated, CTL adhesion to MHC class I results in tyrosine phosphorylation of CTL substrates, phosphatidylinositol (PI) turnover, and degranulation. Although activated adhesion to fibronectin does not itself initiate PI hydrolysis or degranulation, these responses are amplified once they become activated. In the present study we have examined the effect of cis unsaturated fatty acids (FA) and phenylarsine oxide (PAO) on CD8-mediated adhesion of CTL to immobilized class I protein and on biochemical and functional events that are triggered by this adhesion. Previous studies have shown that FA and low concentrations of PAO inhibit specific tyrosine phosphorylation events and degranulation but have no effect on PI turnover or CTL-target cell conjugates. The present results show that pretreating CTL with cis unsaturated, but not saturated, FA and low concentrations of PAO (< 0.5 microM) inhibit soluble anti-TCR-triggered binding of CD8 to immobilized MHC class I, tyrosine phosphorylation of CTL substrates, PI turnover, and degranulation. Addition of cis unsaturated FA or PAO after CTL have been allowed to bind to immobilized class I protein did not affect the level of adhesion. In contrast, neither cis unsaturated FA nor PAO affected the TCR-activated binding of CTL to fibronectin. These results suggest that activation of adhesion to the class I and fibronectin ligands involves divergent different pathways that can be distinguished by the FA and PAO agents.

Animals↗