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R B Levy

Publications and source records attributed to R B Levy.

At least 55 records · Page 3Linked to original sources
PubMed1990

Virus-associated immune responses in mice undergoing GVHR exacerbated by concurrent MCMV infection.

It has been proposed that virus-induced immune responses early postinjection of donor cells can result in the exacerbation of GVH reactions. Previously, we and others have shown that introduction of MCMV together with class I-disparate donor cells results in the development of severe GVH reactions. The present studies were performed to examine the nature of the immune responses induced by concurrent MCMV infection early during GVHR. Within 3 days and continuing through day 10 postinjection, spleens from recipients of virus + GVHR inocula exhibited enhanced cytotoxic activity against YAC-1 target cells effected by a Thy1-Lyt-2-ASGM1+NK1.1+ population. Notably, within one week after virus and GVHR injection, sera from those animals were found to contain specific anti-MCMV IgM antibody at levels comparable to those induced in mice injected only with virus. However, in contrast to recipients of MCMV alone, sera from virus + GVHR animals never contained anti-MCMV IgG antibody. To determine the effect of virus on a discrete donor antihost response, antihost cytotoxic activity was examined. By 7 days postinjection, the spleens of virus + GVHR but not GVHR-only recipients contained marked levels of specific antihost cytotoxic activity, mediated by a Thy1+Lyt-2+ASGM1+NK1.1- population. In total, these findings support the hypothesis that early virus-induced immune responses may promote the development of severe graft-versus-host responses including the enhancement of donor antihost specific cytotoxic T cells.

Animals↗
PubMed1990

The presence of infectious virus but not conventional antigen can exacerbate graft-versus-host reactions.

Previous reports have demonstrated that the introduction of virus (MCMV, HSV-1) concurrent with a graft-versus-host reaction (GvHR) limited to a class I MHC disparity can result in the enhancement of GvHR-associated phenotypic (changes in CD4/CD8 ratio) and functional (inability to produce secondary antibody responses) alterations including the augmentation of in situ natural killer (NK) and donor anti-host cytotoxic T-cell activity. In the present study, we investigated whether immunogens other than infectious virus may be capable of enhancing GvHR. Mice receiving donor cells and the T-dependent antigen dinitrophenyl-bovine serum albumin (DNP-BSA) did not display exacerbated GvHR as evidenced by the absence of phenotypic alterations and the absence of elevated NK activity and the lack of donor anti-host cytotoxic activity. Furthermore, these recipients produced normal levels of IgM and IgG anti-DNP antibody. In addition, mice which received ultraviolet light (UV)-inactivated virus (even at 100 x dosage) together with donor cells also did not exhibit exacerbated GvHR. In total, these findings illustrate a novel ability of infectious virus to exacerbate GvH reactions and are consistent with the hypothesis that viral-induced immune responses may be important in the ability of a pathogen to induce the development of severe GvHR.

Animals↗
PubMed1990

1,25-Dihydroxyvitamin D3 antagonizes interferon-gamma-induced expression of class II major histocompatibility antigens on thyroid follicular and testicular Leydig cells.

Interferon-gamma (IFN gamma) induces production and expression of major histocompatibility complex class II molecules on both marrow-derived and nonbone marrow-derived cell types. 1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3], a seco-steroid derived from vitamin D3, has previously been reported to enhance such expression alone or together with IFN gamma on a number of monocyte/macrophage tumorigenic lines. In contrast, the present studies have found that 1,25-(OH)2D3 inhibited the ability of IFN gamma to induce class II antigen expression on nontransformed rat thyroid follicular epithelial cells (FRTL-5) and mouse testicular Leydig cells (TM3). Although 1,25-(OH)2D3 inhibited the induction of both IA and IE class II locus products, IFN gamma augmentation of class I major histocompatibility complex antigens was not affected. 1,24-(OH)2D3 and 24,25-(OH)2D3 also inhibited class II induction by IFN gamma. Notably, the relative inhibitory ability of these compounds paralleled the strength of their binding affinities for the 1,25-(OH)2D3 receptor, indicating that this antagonistic effect probably requires receptor-ligand interaction. Other steroid hormones, such as hydrocortisone or testosterone, had no inhibitory effect on IFN gamma-induced class II expression on Leydig cells. Additionally, the failure of indomethacin to reverse the effect of 1,25-(OH)2D3 and the finding that exogenous prostaglandin E2 did not inhibit class II induction in these cells indicated that prostaglandins are probably not responsible for this anti-IFN gamma activity. In total, these results suggest that an endocrinological mediator is capable of inhibiting class II induction on resident endocrine tissue populations and, therefore, could help to diminish local CD4+ T-cell recognition of these cells.

24,25-Dihydroxyvitamin D 3↗
PubMed1989

Expression of Ly-6A/E alloantigens in thymocyte and T-lymphocyte subsets: variability related to the Ly-6a and Ly-6b haplotypes.

We have studied the cellular basis for differential expression of the Ly-6A/E alloantigen on T cells obtained from mice of the Ly-6a (10-20% Ly-6A/E+) and Ly-6b (50-60% Ly-6A/E+) haplotypes. During T-cell ontogeny only a small fraction (less than 12%) of thymocytes expressed Ly-6A/E. By 4 weeks of age adult levels of Ly-6A/E bearing lymphocytes were seen in peripheral lymphoid tissue. Immunohistochemical studies of the thymus revealed that Ly-6A/E+ cells were located predominantly in the medulla with small clusters of Ly-6A/E+ cells throughout the cortex. Consistent with this result, phenotypic studies showed that in the adult thymus the majority of Ly-6A/E expression was on mature CD4+CD8- and CD4-CD8+ cortisone-resistant and precursor CD4-CD8- thymocytes. However, a much higher percentage of CD4+CD8- and CD4-CD8- thymocytes as well as CD4+CD8- peripheral T cells expressed Ly-6A/E from Ly-6b mice. Furthermore, although gamma interferon induced increased Ly-6A/E expression in certain thymocyte and T-cell subsets, this induction functioned preferentially for cells obtained from Ly-6b mice. Studies using F1 hybrid mice (Ly-6a x Ly-6b) indicated that the "basal" level of Ly-6A/E expression on these subsets appeared to be under codominant genetic control, whereas gamma interferon-induced regulation of Ly-6A/E expression appeared to be under dominant genetic control. Collectively, these results suggest that the expression of Ly-6A/E on a particular T-cell subset is established in the thymus and is a stable characteristic of each haplotype. In addition, the low levels of Ly-6A/E expression for the Ly-6a haplotype appear to be partially due to the inability of the majority of resting CD4+ T cells to express Ly-6A/E and to the relatively poor induction of this protein by gamma interferon.

Animals↗
PubMed1989

The ability of murine cytomegalovirus and class I major histocompatibility complex-disparate parental cells to induce alterations characteristic of severe graft-versus-host reactions.

The present studies were undertaken to examine the ability of a viral pathogen to enhance immune alterations associated with parent----F1 graft-versus-host reactions (GvHR) across defined donor/recipient MHC genetic disparities. Murine cytomegalovirus (MCMV) was administered concurrently with a parental lymphoid inoculum into unirradiated F1 recipients in strain combinations limiting allogeneic differences to the entire MHC complex (class I/II), the H-2K region (class I), or H-2IA (class II) regions only. Alterations previously found to be associated with GvHR involving changes in the expression of Ly-6, Lyt-2, and L3T4 were examined to characterize the effects of MCMV. Mice receiving low numbers of class I/II-disparate parental cells or MCMV alone failed to exhibit significant GvHR-associated changes. In contrast, introduction of cells and virus resulted in marked alterations characteristic of F1 recipients injected with a large parental cell inoculum alone. Concurrent virus and parental cells could also induce marked changes when administered across differences involving only a class I-disparate--but not class II-disparate only--P----F1 combination. In addition to the phenotypic changes observed during the concurrent virus and class I GvHR, markedly reduced spleen cell proliferative activity and associated weight loss and mortality appeared to indicate that virus had enhanced this reaction. In total, these findings demonstrated that a donor/recipient class I MHC difference was necessary for virus and parental cells to induce the changes observed, and thus not all donor/recipient antigenic differences will result in a similar virus-induced effect. The results are discussed with respect to the potential mechanisms that may account for the apparent exacerbation of GvHR-associated alterations.

Animals↗
PubMed1988

Graft-versus-host reaction-induced immune modulation. I. Donor-recipient genetic disparity and the differential expression of Lyt-2, L3T4, and Ly-6 during acute reactions in the host thymus.

To investigate the effects of graft-vs-host reactions (GvHR) on cells in a central lymphoid compartment, GvHR were induced across class I/II or class II only major histocompatibility complex differences utilizing the parent into nonirradiated F1 hybrid (P----F1) model. Thymocytes were subsequently examined during the acute stage of GvHR for the expression of Lyt-2, L3T4, and Ly-6 cell surface molecules. Class I/II "suppressive" GvHR resulted in a dramatic decrease (greater than 85%) in total thymocyte numbers by 2 wk after parental cell injection. Although a dramatic decrease in the percentages of Lyt-2 (85%----30%) and L3T4 (95%----50%) expression was observed, the percentage of thymocytes expressing Ly-6 was markedly increased compared to uninjected controls (5%----greater than 80%). This increased percentage was not due solely to a selective loss of Ly-6 negative cells from the thymus, since the actual number of Ly-6 positive cells was greater in GvHR mice than in controls. Class II GvHR during the same time interval resulted in a less dramatic decrease (20 to 60%) in total thymocyte numbers. In addition, the effect on the percentages of Lyt-2 (85%----approximately 70%) and L3T4 (95%----approximately 85) expression was subtle and transient. However, intrathymic Ly-6 expression was again clearly enhanced (5%----20 to 30%). Class I/II "proliferative" or "stimulatory" GvHR differ from "suppressive" reactions in that they are characterized by stimulatory pathologic symptoms and the appearance of autoimmune abnormalities. Such GvHR were found to result in minimal alteration of total thymocyte numbers. Similarly, the percentage expression of Lyt-2 and L3T4 was marginally affected. However, the percentage of Ly-6 expression was increased from 5%----20 to 30% and thus these intrathymic lymphocyte profiles more closely resemble those of class II as compared to class I/II "suppressive" GvHR. The present findings therefore demonstrate that major histocompatibility complex differences alone do not necessarily determine the effects of GvHR on recipient thymocytes and that Ly-6 is a useful marker for the early detection of GvHR-associated immunologic events.

Animals↗
PubMed1987

Utilization of antigen specific cytotoxic T-cells as a sensitive approach to investigate the fate of placentally injected allogeneic lymphocytes.

In this report we present a model for the introduction of immunocompetent populations during murine gestation and the subsequent detection of allogeneic cells in the offspring. A highly sensitive in vitro assay, the primed lymphocyte cytotoxicity assay, which can detect extremely low numbers of allogeneic cells residing within host tissue is described. Primed cytotoxic T cells specific for class I antigens were found to be restimulated by as few as 10-50 allogeneic spleen cells from within 10,000 syngeneic neonatal spleen or liver cells. Various tissues derived from neonatal mice which had been placentally injected 1 or 10 days previously were found to contain markedly different percentages of "chimeric" cells in the neonatal organs examined. Notably, while spleen and lung contained more allogeneic cells early following injection, 10 days later the liver contained the highest percentage and the thymus and spleen a significantly lower percentage of allogeneic cells. These findings are discussed with respect to the possible enhancement or depression of the offspring's immune responsiveness following interaction with alloantigen bearing lymphoid cells.

Animals↗
PubMed1985

Molecular localization of allogeneic and self determinants recognized by bulk and clonal populations of cytotoxic T cells.

The localization of MHC-encoded determinants recognized by hapten- and allo-specific cytotoxic T cells was analyzed with the use of cell lines expressing recombinant H-2Dd and H-2Ld MHC products. Bulk cultures of CTL against TNP-self, FITC-self, and AED-self recognized self determinants associated with the N/C1 domains of both Dd and Ld products. A number of allo- and hapten-specific CTL clones were also tested for recognition of the recombinant MHC products. The allo clones specific for Ld or Dd antigens recognized the respective N/C1-associated determinants. In addition, all clones generated against H-2q and known to cross-react with H-2Dd antigens recognized determinants associated with the N/C1-associated Dd determinants. Thus, some of the results obtained with CTL parallel, whereas others contrast with, those findings obtained with monoclonal anti-H-2 antibodies. Similar to the observations made with the monoclonal antibodies, no determinant as defined by T cells has been found to be lost as a result of the interaction between the N/C1 and C2/M domains of the Ld and Dd proteins. Nor did our studies detect the presence of new antigens resulting from the interaction of these gene products. However, the present T cell findings continue to contrast previous results demonstrating that antibody interaction with class I products includes recognition of C2/M-associated epitopes.

Animals↗
PubMed1984

Trinitrophenyl modification of H-2k and H-2b spleen cells results in enhanced serological detection of Kk-like determinants.

Several anti-H-2Kk but not anti-H-2Dd monoclonal antibodies (mAb) exhibited enhanced binding to B10.A murine spleen cells after modification of the cells with trinitrobenzene sulfonate (TNBS). The number of antibody molecules bound to TNP-modified B10.A spleen cells increased by a factor of two or more. The same anti-2Kk mAb that exhibited enhanced binding to modified B10.A cells did not bind to unmodified C57BL/10 spleen cells, as expected, but did bind to TNP-modified C57BL/10 spleen cells. This TNP-dependent binding was not a result of cross-reactions with cell surface TNP groups nor with Fc receptors. TNP modification of a variant cell line that does not express class I H-2 products did not result in enhanced binding by these mAb. These findings can account for preferential recognition of TNP-Kk by B10.A and B10.BR CTL, and also for cross-reactive lysis by C57BL/10 CTL stimulated by C57BL/10-TNP against unmodified H-2Kk targets.

Animals↗
PubMed1984

Thiol groups on the surface of anaerobic parasitic protozoa.

Evidence is presented that Giardia lamblia and Entamoeba histolytica, phylogenetically unrelated aerotolerant anaerobes, have crucial thiol groups on or easily accessible to their external surface. Both parasites were killed by three structurally unrelated thiol-blocking reagents which penetrate intact cells poorly or not at all. The parasites were protected from p-chloromercuribenzenesulfonic acid (10-100 microM) by cysteine or by reduced glutathione. Killing was arrested with identical kinetics by addition of either cysteine (which quickly penetrates the cells) or bovine serum albumin (which does not penetrate intact cells) at various times after p-chloromercuribenzenesulfonic acid, indicating that the reactive site may be on the outer surface of the cell. Proteins lacking cysteine did not protect. Sensitivity of three other protozoa to p-chloromercuribenzenesulfonic acid was also tested. Trichomonas vaginalis (anaerobic) was at least as sensitive as E. histolytica and G. lamblia, while Crithidia fasciculata and Paramecium tetraurelia (both aerobic) were less sensitive. Thiol groups on the G. lamblia surface were demonstrated directly by fluorescence-activated cell sorter analysis of trophozoites which had been modified with a thiol-specific hapten, N-iodoacetyl-N'-(5-sulfonic-1-naphthyl)ethylenediamine and reacted with fluorescent antibody to this hapten.

Anaerobiosis↗
PubMed1983

Graft-vs.-host-associated immune suppression is activated by recognition of allogeneic murine I-A antigens.

Several combinations of F1 hybrid mice were injected intravenously with parental spleen cells to determine the minimal H-2 differences between F1 and parent that are necessary to induce graft-vs.-host-associated immune suppression (GVH-associated suppression). 7-14 d after injection, the spleens of the F1 mice were tested for cytotoxic T lymphocyte potential by in vitro sensitization against trinitrophenyl-self and H-2 alloantigens. The results indicate that parental T lymphocytes must recognize I-A allogeneic determinants of the F1 recipient in order to induce suppression. Recognition of K or D alone or D with I region products other than I-A did not induce suppression. The recognition of I region without K and/or D and even the I-A difference between C57BL/6 and the B6.Cbm12 mutation resulted in immune suppression that was as potent as that resulting from the recognition of K, D, and I together. The possible significance of this function for I-A antigens is discussed with respect to three clinical examples of immune suppression for which this phenomenon may be relevant.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Cross-reactive recognition of alloantigens and certain B6 mutant antigens by antigen-specific and polyclonally activated cytotoxic effector cells.

Various B6 cytotoxic T lymphocyte (CTL) effector populations were tested for cross-reactive lysis (CRL) of unmodified third-party allogeneic as well as of various Kbm and Dbm mutant target cells. The effector cells were generated by in vitro stimulation of B6 spleen cells either from unprimed mice against alloantigen, Con A, or a pool of different allogeneic stimulators, or from in vivo hapten-self primed mice against trinitrophenyl (TNP)-self or N-(5-sulfonic-1-naphthyl)ethylenediame (AED)-self antigens. Except for AED-primed effector cells all CTL populations exhibited significant CRL on third-party allogeneic target cells. More importantly, these alloreactive and H-2-restricted effectors also lysed some of the Kb mutants, but not others. Thus, unmodified bm1 and bm11 mutants were lysed by all of the B6 wild-type effectors, whereas bm6 and bm9 were only weakly lysed by alloreactive CTL. None of the B6 CTL populations lysed bm13 and bm 14 target cells. These data indicate that (a) alloreactive and self-restricted CTL can recognize the same molecular structure of Class I antigens although the epitopes may be different; (b) CTL discriminate between a few amino acid substitutions in certain positions of the H-2 molecule, and (c) the newly generated antigenic determinants of the bm mutants allow them to be divided into three categories in terms of their allogenicity for these cross-reactive CTL populations.

Animals↗
PubMed1983

Cell-mediated lympholytic responses against autologous cells modified with haptenic sulfhydryl reagents. V. H-2Ld self products are recognized by anti-AED-specific cytotoxic T cells.

The present studies were designed to examine the restriction elements involved in the H-2d haplotype CTL response against AED-self. BALB/c mice were immunized by in vivo administration of syngeneic BALB/c spleen cells conjugated with the sulfhydryl reactive haptenic reagent I-AEDANS. The cytotoxic T cell response generated by subsequent in vitro stimulation with AED-self was found to contain H-2K and H-2D region-specific components. In contrast to the predominant H-2D hapten-self CTL responses induced by amino-reactive haptenic reagents like TNBS and FITC, the AED-self response was predominantly directed against H-2K self products. Antibody inhibition analysis demonstrated that the H-2D region component contained Ld-AED-self CTL, as well as Dd-AED-self CTL. However, although both Ld- and Dd-restricted components could be identified shortly (less than 1 wk) after priming, the H-2D region AED-self CTL response shifted to a single restricting molecule, namely Dd, 1 wk and later after immunization. The results of this study provide the first demonstration that the H-2L locus encodes a cell surface product that can function as a restricting molecule for hapten-self-specific CTL. The shift from Ld and Dd AED-specific CTL to Dd only suggests the existence of a highly specific regulatory mechanism directed against antigen (i.e., hapten) plus self.

Animals↗
PubMed1983

The products of transferred H-2 genes express determinants that restrict hapten-specific cytotoxic T cells.

Cell lines into which cloned H-2 genes had been introduced (i.e., transformants) were used to correlate the genes and their products that are capable of functioning as H-2 restriction elements for hapten-self-(AED and TNP) specific cytotoxic T cells (CTL). These transformants provided a unique system in which major histocompatibility restricted (MHC) T cell recognition could be examined by using cells that express only H-2Ld or only H-2Dd gene products. BALB/c (H-2d) anti AED-self CTL lysed both the H-2Ld and Dd transformants, but not parental, i.e., untransformed, cells. The AED-self lysis of the Ld and Dd transformants was shown to be specifically inhibited by anti-H-2Ld and anti H-2Dd monoclonal antibody, respectively. In contrast to these results, BALB/c anti TNP-self CTL were found to lyse readily the Dd but not Ld transformed lines, supporting reports indicating that H-2Ld-restricted TNP-self CTL could not be detected. The results of this study thus demonstrate that the cell surface products encoded by these transferred MHC class I genes contain self determinants recognized by CTL.

Animals↗
PubMed1983

The use of hybrid H-2 genes for localizing the positions of polymorphic determinants recognized by antibodies and by cytotoxic T cells.

Hybrid H-2 genes have been constructed in which the DNA sequences encoding the C2 domains were exchanged between the H-2Ld and H-2Dd genes in order to determine the positions of polymorphic sites of mouse class I antigen. DNA-mediated gene transfer allowed the expression of hybrid H-2 genes in mouse fibroblasts. Binding studies with monoclonal anti-H-2 antibodies against the transformed cells revealed that some serologic determinants were mapped to the C2 domain, while the majority mapped to the N and/or C1 domains. In contrast, uncloned anti-Ld and anti-Dd cytotoxic T lymphocytes predominantly recognized N and/or C1 but not C2 domains. Additionally, all three H-2-restricted hapten-specific cytotoxic T-cell populations (TNP, FITC, and AED) showed predominant detection of N and/or C1 domains.

Animals↗
PubMed1982

Studies on in-vivo priming of the trinitrophenyl-reactive cytotoxic effector-system. III. Are helper T cells involved in the in-vitro generation of cross-reactive as well as restricted cytotoxic responses?

The present study investigates the role of helper cells from trinitrophenyl(TNP)-primed mice in the generation of cytotoxic T lymphocytes (CTL) which lyse TNP-modified syngeneic (TNP-self) targets and cross-reactively lyse TNP-allogeneic target cells. Anti-TNP CTL activities generated from primed (either by intraperitoneal injection of TNP-syngeneic cells or by skin painting with trinitrochlorobenzene) and unprimed spleen cells were compared. When effector populations with comparable lytic activities on TNP-self targets were tested against allogeneic TNP-modified targets, only the in vivo primed effector cells displayed significant cytotoxicity. Since radioresistant helper cells have been found to enhance the anti-TNP-self CTL response, the question was raised whether this helper population could be shown to be involved in the enhanced TNP-allogeneic cross-reactive lysis. Normal spleen cells co-cultured with radioresistant helper cells failed to induce any detectable lysis on TNP-allogeneic targets under conditions for which these helper cells did enhance the lysis detected on TNP-self targets. These results suggest that triggering of such TNP-cross-reactive effector cells during the in vivo priming stage is responsible for the in vitro generation of cross-reactivity.

Animals↗