Thymus dictates major histocompatibility complex (MHC) specificity and immune response gene phenotype of class II MHC-restricted T cells but not of class I MHC-restricted T cells

Association of valine and leucine at HLA-DRB1 position 11 with radiographic progression in rheumatoid arthritis, independent of the shared epitope alleles but not independent of anti-citrullinated protein antibodies

OBJECTIVE

For decades it has been known that the HLA-DRB1 shared epitope (SE) alleles are associated with an increased risk of development and progression of rheumatoid arthritis (RA). Recently, the following variations in the peptide-binding grooves of HLA molecules that predispose to RA development have been identified: Val and Leu at HLA-DRB1 position 11, Asp at HLA-B position 9, and Phe at HLA-DPB1 position 9. This study was undertaken to investigate whether these variants are also associated with radiographic progression in RA, independent of SE and anti-citrullinated protein antibody (ACPA) status.

METHODS

A total of 4,911 radiograph sets from 1,878 RA patients included in the Leiden Early Arthritis Clinic (The Netherlands), Umeå (Sweden), Hospital Clinico San Carlos-Rheumatoid Arthritis (Spain), and National Data Bank for Rheumatic Diseases (US) cohorts were studied. HLA was imputed using single-nucleotide polymorphism data from an Immunochip, and the amino acids listed above were tested in relation to radiographic progression per cohort using an additive model. Results from the 4 cohorts were combined in inverse-variance weighted meta-analyses using a fixed-effects model. Analyses were conditioned on SE and ACPA status.

RESULTS

Val and Leu at HLA-DRB1 position 11 were associated with more radiographic progression (meta-analysis P = 5.11 × 10(-7)); this effect was independent of SE status (meta-analysis P = 0.022) but not independent of ACPA status. Phe at HLA-DPB1 position 9 was associated with more severe radiographic progression (meta-analysis P = 0.024), though not independent of SE status. Asp at HLA-B position 9 was not associated with radiographic progression.

CONCLUSION

Val and Leu at HLA-DRB1 position 11 conferred a risk of a higher rate of radiographic progression independent of SE status but not independent of ACPA status. These findings support the relevance of these amino acids at position 11.

Differential Effects of B and T Lymphocyte Attenuator and Programmed Death-1 on Acceptance of Partially versus Fully MHC-Mismatched Cardiac Allografts

Although fully MHC-mismatched murine cardiac allografts are rapidly rejected, allografts mismatched at only MHC class I or class II alleles survive long term; the immunologic basis for the long-term survival of MHC class I- or II-mismatched allografts is unknown. We examined the roles of two recently described inhibitory receptors, B and T lymphocyte attenuator (BTLA) and programmed death-1 (PD-1), in the survival of partially or fully MHC-mismatched allografts using gene-deficient recipients as well as through use of blocking mAbs in wild-type hosts. Partially MHC-mismatched allografts showed strong induction of BTLA, but not PD-1 mRNA and survived long term in wild-type recipients, whereas targeting of BTLA or its ligand, herpesvirus entry mediator, but not PD-1, prompted their rapid rejection. By contrast, fully MHC-mismatched cardiac allografts were acutely rejected in wild-type recipients despite the induction of both BTLA and PD-1. Targeting of PD-1 in several fully MHC-mismatched models accelerated rejection, whereas targeting of BTLA unexpectedly enhanced PD-1 induction by alloreactive CD4 and CD8 T cells and prolonged allograft survival. In vitro studies using allogeneic dendritic cells and T cells showed that at low levels of T cell activation, BTLA expression was primarily induced, but that with increasing degrees of T cell activation, the expression of PD-1 was strongly up-regulated. These data suggest that BTLA and PD-1 exert distinct inhibitory actions in vivo, with the BTLA/herpesvirus entry mediator pathway appearing to dominate in regulating responses against a restricted degree of allogeneic mismatch.

Immunogenicity of Ly5 (CD45)-antigens hampers long-term engraftment following minimal conditioning in a murine bone marrow transplantation model

Various techniques are available for distinguishing donor from host cells evaluating the efficacy of conditioning regimen for experimental bone marrow transplantation (BMT). Techniques include the use of extracellular immunological markers, such as Ly5 (CD45), and intracellular biochemical markers, such as glucose-phosphate-isomerase (Gpi). Because Ly5 is an extracellular protein, the disparity between donor (Ly5.1) and host (Ly5.2) antigens may induce a weak immune response whereas with Gpi, no immune response is expected. This difference may be of particular concern in experimental transplantation approaches that use minimal conditioning such as low-dose total body irradiation (TBI). Such mild conditioning may not induce the immunosuppression required to overcome host rejection of Ly5 disparate cells. To compare the relative engraftment of Ly5.1 and Gpi-1(a) donor marrow, B6 (Gpi-1(b)/Ly5.2) mice were irradiated with low-level TBI (0-6 Gy) and transplanted with several bone marrow (BM) doses (2 x 10(6)-5 x 10(7) cells). At 8, 26, and 52 weeks post-BMT, the level of donor engraftment was measured using flow cytometry (Ly5) or Gpi-electrophoresis. Lower engraftment levels were found in mice transplanted with Ly5 congenic BM in groups given low-dose TBI (< or = 4 Gy) and/or low doses of BM cells (BMC) (2 x 10(6)). However, when higher TBI or BMC doses were used, similar engraftment levels were found, suggesting sufficient immune suppression to allow equal engraftment of both sources of BM. These data suggest that even a minor phenotypic disparity between donor and host, such as Ly5, may necessitate high-dose TBI to prevent rejection. The combination of low-dose TBI or other nonmyeloablative conditioning strategies with small numbers of BMC may lead to reduced engraftment when extracellular immunological markers such as Ly5 are used for transplantation studies. Therefore, small immunological differences must be considered when using the Ly5 marker for engraftment.

Surgical technique for vascularized thymus transplantation in mice

Traditionally, mouse nonvascularized thymus implants have been used to investigate various aspects of thymus function. However, these grafts are easily damaged by ischemia and fail to reproduce the normal anatomy of the thymus. In addition, the function of these grafts has not been fully examined. We have recently developed a vascularized thymus transplant model in mice. The donor operation consists of isolating the right lobe of the thymus and creating a single vascular pathway. In the recipient surgery, end-to-side anastomoses between donor brachycephalic artery and recipient right common carotid artery, and between donor superior caval vein and recipient right external jugular vein, were performed. We performed 10 consecutive isografts in BALB/c mice with a success rate of 90%. The thymus grafts had a normal histology and function. This study illustrates that it is technically possible to transplant a mouse vascular thymus graft. This model has several advantages that make it a useful tool to study many aspects of thymus function. We plan to use this model further to study the potential for induction of tolerance by thymus grafts.

Transplantation of thymus tissue in complete DiGeorge syndrome

BACKGROUND

The DiGeorge syndrome is a congenital disorder that affects the heart, parathyroid glands, and thymus. In complete DiGeorge syndrome, patients have severely reduced T-cell function.

METHODS

We treated five infants (age, one to four months) with complete DiGeorge syndrome by transplantation of cultured postnatal thymus tissue. Follow-up evaluations included immune phenotyping and proliferative studies of peripheral-blood mononuclear cells plus biopsy of the thymus allograft. Thymic production of new T cells was assessed in peripheral blood by tests for T-cell-receptor recombination excision circles, which are formed from excised DNA during the rearrangement of T-cell-receptor genes.

RESULTS

After the transplantation of thymus tissue, T-cell proliferative responses to mitogens developed in four of the five patients. Two of the patients survived with restoration of immune function; three patients died from infection or abnormalities unrelated to transplantation. Biopsies of grafted thymus in the surviving patients showed normal morphologic features and active T-cell production. In three patients, donor T cells could be detected about four weeks after transplantation, although there was no evidence of graft-versus-host disease on biopsy or at autopsy. In one patient, the T-cell development within the graft was demonstrated to accompany the appearance of recently developed T cells in the periphery and coincided with the onset of normal T-cell function. In one patient, there was evidence of thymus function and CD45RA+CD62L+ T cells more than five years after transplantation.

CONCLUSIONS

In some infants with profound immunodeficiency and complete DiGeorge syndrome, the transplantation of thymus tissue can restore normal immune function. Early thymus transplantation - before the development of infectious complications - may promote successful immune reconstitution.

Tumor eradication by wild-type p53-specific cytotoxic T lymphocytes

The tumor suppressor protein p53 is overexpressed in close to 50% of all human malignancies. The p53 protein is therefore an attractive target for immunotherapy. Cytotoxic T lymphocytes (CTLs) recognizing a murine wild-type p53 peptide, presented by the major histocompatibility complex class I molecule H-2Kb, were generated by immunizing p53 gene deficient (p53 -/-) C57BL/6 mice with syngeneic p53-overexpressing tumor cells. Adoptive transfer of these CTLs into tumor-bearing p53 +/+ nude mice caused complete and permanent tumor eradication. Importantly, this occurred in the absence of any demonstrable damage to normal tissue. When transferred into p53 +/+ immunocompetent C57BL/6 mice, the CTLs persisted for weeks in the absence of immunopathology and were capable of preventing tumor outgrowth. Wild-type p53-specific CTLs can apparently discriminate between p53-overexpressing tumor cells and normal tissue, indicating that widely expressed autologous molecules such as p53 can serve as a target for CTL-mediated immunotherapy of tumors.

Cytotoxic T lymphocytes raised against a subdominant epitope offered as a synthetic peptide eradicate human papillomavirus type 16-induced tumors

Previously, we have shown that immunization with human papillomavirus (HPV) type 16-derived cytotoxic T lymphocyte (CTL) epitope E7 49-57 (RAHYNIVTF) renders C57BL/6 mice insensitive to tumors formed by HPV16-transformed cells. In this study, we provide evidence that E7 49-57 is expressed as a subdominant CTL epitope on HPV16-transformed C57BL/6 cells. Using acid peptide elution, it is shown that HPV16-transformed cells express another CTL epitope, besides E7 49-57, which appears to be dominant. We demonstrate that a CTL line raised against the subdominant CTL epitope, offered as synthetic peptide E7 49-57, eradicates established HPV16-induced tumors in mice. Our data show that synthetic peptide-induced CTL can be applied successfully in vivo against (virus-induced) tumor, and emphasize that subdominant CTL epitopes are useful targets for immunotherapy. Furthermore, it is illustrated for the first time that HPV16-specific CTL interfere directly with HPV16-induced tumors.

Identification of an H-2 Kb-presented Moloney murine leukemia virus cytotoxic T-lymphocyte epitope that displays enhanced recognition in H-2 Db mutant bm13 mice

Upon infection with the Moloney murine sarcoma virus-murine leukemia virus (MuLV) complex, H-2b C57BL/6 (B6) mice respond with a class I Db-restricted cytotoxic T-lymphocyte (CTL) response, which protects against virus-induced tumorigenesis. In the B6-derived Db mutant B6.CH-2bm13 (bm13) strain, part of the class I Db antigen-presenting groove is shaped by a class I Kb-encoded sequence. Like B6 mice, bm13 mice reject Moloney virus-induced tumors, but the protective CTL response is Kb restricted. In this study we show enhanced levels of Moloney MuLV-specific CTLp with a restriction for Kb in bm13 mice. Through the use of CTL clones from Moloney virus-immunized bm13 mice, the class I Kb-presented CTL epitope was identified. The epitope is located in the Moloney virus gp70 envelope protein region (Moloney envelope, amino acids 189 to 196 [Mol env (189-196)]), SSWDFITV and has the Kb allele-specific binding motif. The Dbm13 molecule does not present the env(189 to 196) epitope to Kb-restricted bm13 CTL. In B6 mice, Mol env(189-196)-specific CTL could be induced by peptide vaccination. B6 mice thus have CTL precursors specific for this epitope but at considerably lower levels than do bm13 mice. We hypothesize that additional positive selection of Kb-restricted CTL on the Dbm13 molecule in bm13 mice explains this difference in precursor frequencies. We examined related strains of MuLV for the presence of Mol env(189-196) sequence equivalents. Rauscher, Friend, and AKV MuLV-encoded Mol env(189-196) epitope equivalents were properly recognized in cytotoxicity assays, both as synthetic and as endogenously expressed (Rauscher MuLV) peptides. In contrast, the mink cell focus-forming virus MuLV-encoded epitope equivalent, lacking a Kb anchor residue, was not presented for CTL recognition and hence can be excluded as an important CTL epitope for mink cell focus-forming viruses.

Differential recovery of polymorphonuclear neutrophils, B and T cell subpopulations in the thymus, bone marrow, spleen and blood of mice following split-dose polychemotherapy

In these studies, we examined the effect of a maximum-tolerated, split-dose chemotherapy protocol of cyclophosphamide, cisplatin, and 1,3-bis(2-chloroethyl)-1-nitrosourea carmustine on neutrophil and lymphocyte, subpopulations in the peripheral blood (PBL), thymus, bone marrow and spleen. It was found that this protocol of polychemotherapy, modeled after the induction protocol used with autologous bone marrow transplantation for breast cancer, suppressed both B and T cell populations and T cell function at times when the absolute neutrophil count had returned to normal or supernormal numbers. In the peripheral blood, 7 days following initiation of chemotherapy, there was a twofold increase in the percentage of granulocytes as compared to the level in control animals on the basis of a differential count. The polymorphonuclear neutrophil (PMN) frequency in the bone marrow was increased on day 14 and statistically identical to that in control mice on all other days analyzed. In contrast to the bone marrow cells and PBL on day 7, the frequency of PMN in the spleen and thymus was depressed. B cells (B220+) were depressed in the pBL, spleen and bone marrow and took 18-32 days to return to their normal frequency, while the frequency of B cells in the thymus was increased owing to a loss of immature T cells. The percentage of CD3+ cells in the thymus, spleen and bone marrow was significantly increased and required 10-18 days to return to normal levels, while the absolute number of CD3+ cells in the blood varied around the normal value. The ratio of CD4+ to CD8+ cells in all the organs studied varied only slightly owing to a similar reconstitution of CD4+ and CD8+ cells. In contrast to the phenotypic recovery of the CD3+, CD4+, and CD8+ cells, the ability of the splenic lymphocytes to respond to concanavalin-A was depressed and remained depressed, despite the phenotypic reconstitution of the T cell subsets, on the basis of both percentage and absolute cell number. These results show a selective T and B cell depression following multi-drug, split-dose chemotherapy in tissue and blood leukocyte populations and a chronic depression in T cell function.

Compromising effect of low dose-rate total body irradiation on allogeneic bone marrow engraftment

The protraction of total body irradiation (TBI) to a continuous low dose-rate has been investigated for its effect on donor marrow engraftment in murine bone marrow transplant (BMT) models of varying histocompatibility. Three different BMT combinations were used: syngeneic [B6-Gpi-1a-->B6-Gpi-1b], H-2 compatible allogeneic [BALB.B (H-2b)-->B6 (H-2b)] and H-2 mismatched allogeneic [BALB/c (H-2d)-->B6 (H-2b)]. TBI was delivered over a range of doses at either a high (HDR, 40 cGy/min) or low (LDR, 2 cGy/min) dose rate followed by infusion of 10(7) bone marrow cells from syngeneic or allogeneic donors. The level of donor (Gpi-1a) engraftment was determined from blood Gpi-typing at different times after TBI and BMT. Radiation dose-response relationships corresponding to long-term haemopoietic engraftment at 20 weeks showed a dose-sparing effect of LDR that became more prominent with increasing genetic disparity between donor and host. For fully allogeneic (H-2 incompatible) BMT, a dose as high as 16Gy LDR was still not sufficient for achieving chimerism in all recipients. In many cases allogeneic BMT gave transient blood chimerism enabling the recipient to survive the acute effects of high dose TBI with full long-term repopulation from surviving stem cells of the host. Radiation cell survival curves were obtained for the frequency of alloreactive precursors of proliferating T-lymphocytes (pPTL) remaining in the spleen at 1 day after TBI. A radiation dose-sparing effect of LDR was also found for pPTL depletion. These data suggest that radiation damage repair during LDR irradiation in an immunocyte target cell population is mainly responsible for enhanced graft rejection thus rendering protracted TBI less effective for application in clinical allogeneic BMT.

Positive selection of the T-cell repertoire is affected by mutations in the peptide-binding site of MHC class I molecules

H-2Kb mutant molecules (H-2Kbm) and the H-2Kb-restricted response to OVA and VSV N peptides were used to investigate the influence of polymorphism of structurally defined regions of the MHC class I molecules on intrathymic positive selection of the T-cell repertoire. We show that the positive selection of the T-cell repertoire in the thymus requires the self-peptide to be present in the MHC antigen-binding site. A correlation between the ability of four MHC molecules to present antigenic peptide and to positively select T cells specific for it was noted. The self-peptides involved in positive selection may therefore mimic the foreign peptide during intrathymic selection. A structural correlate of this mimicry may be a similar or identical binding requirement for the antigen-binding pocket(s)/residues of the MHC peptide-binding site.

Class II-positive hematopoietic cells cannot mediate positive selection of CD4+ T lymphocytes in class II-deficient mice

Generation of immunocompetent alpha/beta T-cell receptor-positive T cells from CD4+CD8+ thymocytes depends upon their interaction with thymic major histocompatibility complex (MHC) molecules. This process of positive selection provides mature T cells that can recognize antigens in the context of self-MHC proteins. Previous studies investigating haplotype restriction in thymic and bone-marrow chimeras concluded that radioresistant thymic cortical epithelium directs the positive selection of thymocytes. There is controversy, however, as to whether intra- or extrathymic radiosensitive bone marrow-derived macrophage and dendritic cells also can mediate positive selection. To determine whether CD4+ T cells can be positively selected by hematopoietic cells, we generated chimeric animals expressing MHC class II molecules on either bone marrow-derived or thymic stromal cells by using a recently produced strain of MHC class II-deficient mice. CD4+ T cells developed only when class II MHC molecules were expressed on radioresistant thymic cells. In contrast to what recently has been observed for the selection of CD8+ T lymphocytes, MHC class II-positive bone marrow-derived cells were unable to mediate the selection of CD4+ T cells when the thymic epithelium lacked MHC class II expression. These data suggest that CD4+ and CD8+ T cells may be generated by overlapping, but not identical, mechanisms.

Extrathymic positive selection of αβ T-cell precursors in nude mice

T lymphocytes expressing alpha beta T-cell receptors with sufficient affinity to major histocompatibility complex (MHC) molecules expressed on thymus epithelial cells are positively selected and mature to functional T cells. But several studies have demonstrated that athymic nude mice grafted with MHC-incompatible thymuses developed T cells specific for nude host rather than thymic MHC. We examined this paradox by analysing the specificity of T lymphocytes derived from nude mice. We report here that nude T lymphocyte precursors transferred to allogeneic SCID (severe combined immunodeficiency) mice with a functioning thymus (but lacking T or B cells) generated host MHC-restricted effector T cells but also contained T cells restricted to donor MHC. If nude T cells were depleted from nude lymphohaemopoietic donor cells before or after transfer, only host MHC-specific T cells matured. The results may explain the unusual MHC specificities of nude T lymphocytes described in earlier studies and demonstrate two separate differentiation steps: in nude mice, T cells may be positively selected for self-MHC restriction specificity extrathymically; then a functional thymus is required for efficient T cell maturation.

Neonatal tolerance induction in the thymus to MHC-class II-associated antigens. IV. Significance of intrathymic chimerism of blood-born Ia+ cells in Mls tolerance

The significance of thymus cell chimerism in the induction and maintenance of tolerance was investigated. Mls-1b BALB/c mice were neonatally tolerized by the intravenous administration of either bone marrow (BM) cells or peritoneal cavity (PerC) cells from Mls-1b/a (BALB/c x AKR) F1 mice. Tolerance was long-lasting in the BM cell group, but transient in the PerC cell group, probably because PerC cells lack hemopoietic stem cells required for a continuous supply of tolerance-inducing cells. The degree of anti-Mls-1a responsiveness of these BALB/c thymus cells was correlated with the degree of intrathymic distribution of the inoculated F1 cells. The effect of BM cell inoculation, resulting in a year-long deletion of Mls-1a-reactive V beta 6-bearing T cells is in marked contrast to that of PerC cell inoculation which causes only a transient loss of V beta 6+ mature thymocytes (for about 1 week after birth). This functional profile of the tolerant state correlates well with the degree and persistence of the intrathymic presence of F1 type Ia+ cells. The long-lasting presence of donor-derived cells throughout the thymus tissue in the BM cell group is also in marked contrast to the early disappearance of Ia+ cells (within 2-3 weeks) from the cortex and then from the medulla in the PerC cell group, although these Ia+ cells were once spread throughout the thymus tissue 4 days after the tolerance-inducing cell inoculation. Taken together with a failure to induce consistent unresponsiveness to Mls-1a determinants in Mls-1b thymocytes regenerating in Mls-1a-thymic epithelial environments, all the above data indicate that intrathymic chimerism caused by hemopoietic stem cell-derived MHC-class II-bearing cells is a requisite for the induction and maintenance of unresponsiveness by means of clonal deletion in experimentally as well as naturally induced tolerance to Mls determinants.

Peptide presentation by class-I major histocompatibility complex molecules

MHC class-I molecules express distinct peptide-binding pockets within their antigen-binding groove. These are critically involved in the binding of antigenic peptides. The amino acid composition of a pocket dictates the structure of a peptide which can be bound in it. This is evident as a consensus amino acid motif which has to exist within a peptide in order for it to bind to a particular MHC allele. Perturbation of a MHC pocket by amino acid substitution can result in the abolition of peptide binding. Less drastic mutations of the peptide-binding groove, particularly the ones away from the critical pocket, can subtly alter the conformation of bound peptide. Both types of substitution exert an influence on the TCR recognition of antigenic peptide. Peptides are also critically involved in the positive selection of the class-I-restricted TCR repertoire in the thymus. These self peptides act by mimicking their foreign antigens. This mimicking involves the binding of self peptides and foreign antigenic peptides to the same pockets of the MHC class-I-antigen binding groove. Consequently, MHC class-I polymorphism in the antigen binding groove controls the intrathymic positive selection and peripheral antigen presentation by the same mechanisms. The majority of positively selecting self peptides could well originate from the extracellular processing of circulating self proteins. Using the diverse, extracellularly generated self peptides and the different determinant density requirements for positive versus negative selection, the immune system can ensure the repertoire diversity, avoiding both the massive clonal deletion of the selected repertoire and the autoreactivity of its T cells.

MHC class II-restricted T-cell hybridomas recognizing the nucleocapsid protein of avian coronavirus IBV

Mice were immunized with purified infectious bronchitis virus (IBV), strain M41. Spleen cells, expanded in vitro by stimulation with M41, were immortalized by fusion to obtain T-cell hybridomas, and two major histocompatability complex (MHC) class II (I-E)-restricted T-cell hybridomas were selected with specificity for IBV. Both hybridomas selectively recognized the internal nucleocapsid protein. The responses to 12 different strains of IBV varied markedly. This demonstrates antigenic variation of the nucleocapsid protein in addition to the known variation of the surface glycoprotein S.

CD4 rat x rat and mouse x rat T cell hybridomas produced by fusion of established T cell lines and clones to W/Fu (C58NT)D

Previously, fusion of established T cell lines or clones has been claimed to be difficult. We now report our experiences in the fusion of both long term cultures of rat T cell clones and mouse T cell lines to rat W/Fu (C58NT)D. Upon fusion of rat T cell clones the hybrids obtained expressed antigen specificities identical to those of the parent clones. In addition, C58 was used for interspecies hybridisation of murine T cell lines. The specificity of intra- and inter-species hybrids was maintained by subcloning. We conclude that the C58 cell line can be used to generate continuously growing monoclonal T-cell reagents of sufficient stability using both intra- and inter-species hybridisation.

IgG antibody and delayed-type hypersensitivity responses in nude mice grafted with thymic epithelium

This study compared the ability of foetal thymic epithelium depleted of lymphocytes and dendritic cells, by low temperature or deoxyguanosine (dGuo) treatment in organ culture, to reconstitute T-cell function in nude mice. It is shown that renal capsule grafts of either type could promote the development of functional T lymphocytes in the periphery, as judged by in vivo assays. Both syngeneic and allogeneic thymic epithelium endowed nude mice with the capacity to mount IgG antibody and delayed-type hypersensitivity (DTH) responses to the T-dependent antigen ovalbumin (OVA). Functional reconstitution was accompanied by the appearance of Thy-1-bearing cells in the spleens of thymic grafted nude mice. The results from allogeneically grafted recipients show that a substantial population of peripheral T cells was present that collaborated with B cells and other antigen-presenting cells (APC) which do not express major histocompatibility complex (MHC) molecules of the thymus donor haplotype.

Abnormal anti-viral immune response in mice is corrected in HLA-B27.2-transgenic mice

In contrast to the strong Sendai virus-specific cytotoxic T-lymphocyte (CTL) responses in C57BL/6 mice. H-2Kb mutant bm1 mice are nonresponders to Sendai virus. By appropriate crossings between HLA-B27 double-transgenic mice and Kb mutant bm1 mice, and after subsequent selection, H-2bm1 homozygous mice were produced expressing the human HLA-B27.2 and beta 2-microglobulin genes. Here we show that the introduction of a human HLA class I gene into the genome of the H-2bm1 Sendai virus-nonresponder mutant mice resulted in good responsiveness to Sendai virus, and in normal levels of Sendai virus-specific CTL precursors. The CTL response in the HLA-B27.2 double-transgenic H-2bm1 mice against Sendai virus was restricted by the HLA-B27.2 molecule. These results show the direct involvement of HLA class I molecules in regulation of the anti-viral CTL repertoire and represent for the first time a correction of abnormal anti-viral immunity in mice by incorporation of a human MHC class I (HLA-B27.2) gene.

Development of T cells in vitro from precursors in mouse bone marrow

Bone marrow cells from 6- to 8-week-old athymic nude mice were depleted of nylon-wool adherent cells and cultured in vitro at low cell numbers (300 cells/well) in medium supplemented with a supernatant from a thymoma cell line. About 1% of cultured cells grew. Pooled cultures contained cells expressing CD3 (52%), CD4 (37%), CD8 (11%), Thy 1.2 (72%), MAC-1 (43%) and J11d (86%) but no cells expressing sIg. They also contained cells expressing mRNA for the alpha, beta, gamma, and delta chains of the T cell receptor as assessed with C region probes using a sensitive dot blot assay. These cells appear to develop from progenitors which are CD3-. When pooled Day 10 cultures were depleted of nylon-wool adherent cells, the remaining cells were nearly all J11d+, Thy 1.2+, MAC-1-, CD3+, and either CD4+CD8+; CD4+CD8-; CD4-CD8+, or CD4-CD8-; i.e., their surface marker patterns were reminiscent of those of thymocytes. We conclude that our culture system is enabling bone marrow precursors to commence differentiation down the T cell lineage in the absence of a thymic environment.

Thymic requirement for clonal deletion during T cell development

During T cell differentiation, self tolerance is established in part by the deletion of self-reactive T cells within the thymus (negative selection). The presence of T cell receptor (TCR)-alpha beta + T cells in older athymic (nu/nu) mice indicates that some T cells can also mature without thymic influence. Therefore, to determine whether the thymus is required for negative selection, TCR V beta expression was compared in athymic nu/nu mice and their congenic normal littermates. T cells expressing V beta 3 proteins are specific for minor lymphocyte stimulatory (Mlsc) determinants and are deleted intrathymically due to self tolerance in Mlsc+ mouse strains. Here it is shown that V beta 3+ T cells are deleted in Mlsc+ BALB/c nu/+ mice, but not in their BALB/c nu/nu littermates. Thus, the thymus is required for clonal deletion during T cell development.

Eradication of adenovirus E1-induced tumors by E1A-specific cytotoxic T lymphocytes

Cytotoxic T lymphocyte (CTL) clones against adenovirus type 5 (Ad5) early region 1 (E1)-transformed cells were generated in C57BL/6 (B6) mice. A defined peptide encoded by Ad5 E1A is the target structure for H-2Db-restricted CTLs. Upon intravenous injection into B6 nude mice bearing Ad5 E1-induced tumors, these CTLs, if combined with recombinant IL-2, destroy subcutaneous tumor masses up to 10 cm3. The in vivo action of CTLs is highly specific, and long-term "memory" persists in treated nude mice months after tumor regression. Our data show an important role for CTLs directed against a viral nuclear oncogene product in tumor eradication.

Cyclosporin A and anti-Ia antibody cause a maturation defect of CD4+8- cells in organ-cultured fetal thymus

The effects of anti-Ia antibodies and cyclosporin A (CsA) on phenotypic differentiation of murine thymocytes were assessed in organ-cultured fetal thymuses. Both agents specifically abrogated the generation of CD4+8- thymocytes. Immunohistochemical studies revealed that Ia antigen on the organ-cultured thymic epithelial cells did not disappear with the addition of the agents, although anti-Ia antibody was proved to bind to Ia antigen during the culture. On the other hand, CsA neither changed the expression of Ia nor bound to it. As CsA is known to block the signalling cascade initiated by perturbation of T-cell receptor (TcR), it is suggested that both the Ia expression in the thymus and the signalling via receptors on thymocytes, the signals presumably generated by TcR binding to class II MHC molecules, might be necessary for phenotypic differentiation of class II MHC-restricted T cells (CD4+8- cells), but not for class I MHC-restricted T cells (CD4-8+).

Macrophages phagocytose thymic lymphocytes with productively rearranged T cell receptor alpha and beta genes

The thymus gland is important for the formation of competent T lymphocytes. However, there is long-standing evidence that greater than 95% of newly formed thymocytes do not emigrate to peripheral lymphoid tissues but instead die locally. We have identified a rapid and selective pathway for thymocyte turnover in vitro. The mechanism entails binding, uptake, and digestion by macrophages. The susceptible cells are a subpopulation of double-positive thymocytes. These thymocytes can be enriched by virtue of their high buoyant density in Percoll and prove to have low levels of surface CD3 and little or no surface TCR. However TCR-alpha and -beta genes have undergone rearrangement, and full length alpha and beta transcripts are abundant. Therefore many double-positive cells rearrange and express TCR genes but do not have normal levels of TCR on the cell surface. We propose that thymocytes that undergo high turnover in situ are unable to form receptors that can be selected by MHC molecules in the thymus, and that these cells are recognized and cleared by the macrophage.

Distinct patterns of virus-specific T cell-mediated cytolysis of transformed versus primary target cells

Ideas about the mechanism(s) by which cytotoxic T lymphocytes (CTL) lyse appropriate target cells are still controversial. We studied the action of established murine CTL clones as well as of freshly prepared primarily induced CTL against two types of target cells. Transformed tumour cell lines (MC57G and L929) and untransformed cells such as peritoneal exudate cells (PEC) or fibroblasts were examined as target cells by scanning and transmission electron microscopy and with the 51Cr-release assay. We found independent of which CTL used, that in transformed cells the cell membrane seemed to be the first target of CTL attack, whereas in untransformed cells the first noticeable events appeared to take place in the nucleus of the target cells; the membrane of attacked untransformed PEC or fibroblasts was found to be intact at a time when the cellular organelles already were disintegrated. The morphological observations were paralleled by differences in the kinetics of 51Cr-release; untransformed target cells released their label only after a 2 h long period, whereas transformed cells released 51Cr considerably earlier.

Cell-mediated immunity induced in mice after vaccination with a protease activation mutant, TR-2, of Sendai virus

Our previous study has shown that, although a trypsin-resistant mutant of Sendai virus, TR-2, replicates only in a single cycle in mouse lung with a negligible lesion, the animal acquires a strong immunity against lethal infection with wild-type Sendai virus, suggesting that TR-2 could be used as a new type of live vaccine (M. Tashiro and M. Homma, J. Virol. 53:228-234, 1985). In the present study, we investigated the immunological response elicited in TR-2-infected mice, particularly with respect to cell-mediated immunity. Analyses of cytotoxic activities of spleen cells with 51Cr release assays revealed that Sendai virus-specific T lymphocytes (CTL), in addition to natural killer activity and antiviral antibodies, were induced in DBA/2 and C3H/He mice infected intranasally with TR-2. Proteolytic activation of the fusion glycoprotein F was required for the primary induction of CTL, though not necessarily for stimulation of natural killer and antibody responses. Memory of the CTL induced by TR-2 was long-lasting and was recalled in vivo immediately after challenge with wild-type Sendai virus. In contrast to TR-2, immunization with inactive split vaccine failed to induce the CTL response, but it elicited a high titer of serum antibody and a low level of natural killer activity.

Lymphocyte depletion in thymic nurse cells: a tool to identify in situ lympho-epithelial complexes having thymic nurse cell characteristics

In situ pre-existing complexes of epithelial cells and thymocytes having thymic nurse cell characteristics were visualized in the murine thymus cortex using dexamethasone as a potent killer of cortisone-sensitive thymocytes. The degradation and subsequent depletion of cortisone-sensitive thymocytes enclosed within cortical epithelial cells appeared to be paralleled by thymocyte degradation and depletion in thymic nurse cells isolated from thymic tissue fragments from dexamethasone-treated animals. This suggests that thymic nurse cells are derived from pre-existing sealed complexes of cortical epithelial cells and thymocytes. Not all thymocytes situated within in situ epithelial or thymic nurse cells complexes appear to be cortisone-sensitive: a minority of 1-2 thymocytes per complex survives the dexamethasone-treatment, thus constituting a minor subset of cortical cortisone-resistant thymocytes predominantly localized within cortical epithelial cells in situ and within thymic nurse cells derived from such structures. Cortisone resistance in thymocytes thus seems to be acquired within the cortical epithelial cell microenvironment. Cortisone-resistant thymocytes in thymic nurse cells express the phenotype of mature precursors of the T helper lineage, indicating that the in situ correlates of thymic nurse cells may play an important role in T cell maturation and selection.

Cytokine activity after human bone marrow transplantation. II. Production of macrophage procoagulant activity and the cytokine regulating its production, macrophage procoagulant inducing factor

The production of procoagulant activity by circulating monocytes and its regulation by a cytokine secreted by mitogen-stimulated peripheral blood mononuclear cells was investigated in recipients of HLA-identical sibling bone marrow transplants. Blood monocyte numbers reached the normal range within 3 weeks of transplant. After stimulation with lipopolysaccharide, macrophage procoagulant activity was found to be within the normal range in all patients at all times post transplant. It did not appear to correlate with the presence or absence of graft-versus-host disease. Surprisingly, and in marked contrast to our previously documented severe depression of interleukin 2 production by transplant recipients' peripheral blood mononuclear cells, the mitogen-induced production of the cytokine that induces procoagulant activity production (macrophage procoagulant inducing factor, MPIF) was also normal in the majority of patients when assayed using the responsive myelomonocytic cell line RC-2A. These findings suggest firstly that monocyte differentiation and function normalize rapidly post transplant; and secondly, when taken together with previous studies, that the ability of peripheral blood mononuclear cells to synthesize cytokines post transplant varies greatly according to the specific cytokine involved.

Development of CD4-CD8+ cytotoxic T cells requires interactions with class I MHC determinants

Differentiation of bone marrow derived precursors into mature T cells takes place in the thymus. During differentiation, T cells develop the receptor repertoire which allows them to recognize antigen in the context of self major histocompatibility complex (MHC) molecules. Mature T helper cells (mostly CD4+ CD8-) recognize antigen in the context of class II MHC molecules, whereas cytotoxic T cells (mostly CD4-CD8+) recognize antigen in the context of class I MHC determinants. Thymic MHC-encoded determinants greatly influence the selection of the T-cell receptor repertoire. In addition to positive selection, a negative selection to eliminate self-reactive T-cell clones is thought to occur in the thymus, but how this 'education' occurs is not well understood. It has been suggested that during differentiation an interaction between the T-cell receptor (TCR) and MHC-encoded determinants occurs, leading to the selection of an MHC-restricted receptor repertoire. In support of this hypothesis, class-II-specific, CD4+ CD8- helper T cells fail to develop in mice neonatally treated with anti-class II monoclonal antibody (mAb). As CD4-CD8+ cells differ from the CD4+ CD8- lineage (in function, MHC-restriction specificity and perhaps site of education) we examined whether interactions with MHC determinants are also necessary for the development of class-I-specific T cells. Here we show that mice chronically treated with anti-class I mAb from birth lack CD4-CD8+ cells and cytotoxic T-cell precursors, indicating that most CD4-CD8+ T cells need interaction with class I MHC molecules during differentiation.

Neonatal tolerance induction in the thymus to MHC-class II-associated antigens. III. Significance of hemopoietic stem cells for induction and maintenance of Mls tolerance by continuous supply of tolerance-inducing nonlymphocytes

The role of hemopoietic stem cells and other cell types in the induction and maintenance of immunologic tolerance in the thymus was investigated by intravenous injection of Mls-semi-allogeneic cells into newborn mice less than 24 hr after birth. Mls-specific tolerance was induced by inoculation of peritoneal cells and thymus cells, and the tolerant state was compared with that induced by bone marrow cells which had hemopoietic stem cell activity and were able to create a stable chimera in both central and peripheral lymphoid organs. When peritoneal or thymus cells were injected, the level of tolerance attained was proportional to the number of cells injected, though peritoneal cells were 20 times as effective as thymus cells. In vivo functions of tolerance-inducing cells and their immediate precursors were radiosensitive and belonged to a Thy-1-, nylon-wool-nonadherent (probably non-B), weakly Sephadex G-10-adherent cell population. Tolerance induced by peritoneal cell injections was transient, starting to terminate within the first 2 weeks of life, while tolerance caused by bone marrow cell injections persisted through more than 6 weeks. Such transient tolerance induced by the former became long-lasting when followed by an additional injection of bone marrow cells, which did not cause thymic lymphocyte chimerism. All data indicated that bone marrow stem cells were engaged in tolerance induction and maintenance by continuously supplying tolerance-inducing nonlymphocytes.

Role of natural killer (NK) cells in the production of the murine T lymphocyte allorecognition repertoire

Limiting dilution cultures of alloreactive (anti-H2Kb) CTL were established from thymocyte or spleen cell pools of C3H/HeJ and their congenic bg/bg partner, or of SJL/J and their congenic bg/bg partner. CTL populations in these cultures were assayed for cross-reactive lysis of a panel of splenic Con A blasts of H2Kbm mutant mice. There was some slight elevation of frequency of CTLp in the thymocyte lymphoid pool of bg/bg mice; more strikingly, the repertoire of anti-H2Kb specificities was clearly altered in both strains in the bg/bg animals. There was apparently an increased diversity (more specificities represented at higher frequencies) in the thymocyte pool and a decreased diversity in the spleen cell CTLp pool in animals with the bg/bg marker. Similar shifts in the allorecognition repertoire of normal C3H/HeJ mice were produced by inoculation of neonatal mice with a rabbit anti-NK heteroantibody (antiasialo GM1). Preabsorption of this serum such that it lost anti-NK activity also abolished this effect of in vivo neonatal injection. Furthermore, injection of bg/bg bone marrow-reconstituted C3H/HeJ (bg/+) mice with a C3H spleen cell-derived NK line also caused a shift in the allorecognition repertoire toward that seen in the normal littermate control animals.

Thymic immune response gene function in radiation chimeras reconstituted with purified hemopoietic stem cells

Thymectomized (C57BL/6[B6] X bm1)F1 mice and thymectomized (B6 X bm12)F1 mice were engrafted with neonatal parental thymus of either B6 type [H-2b mouse, Sendai virus cytotoxic T cell (Tc) responder] or bm1 type (H-2Kb mutant, Sendai virus Tc nonresponder) and B6 type (H-Y Tc responder) or bm12 type (H-2 I-Ab mutant, H-Y Tc nonresponder), respectively. All mice were irradiated and reconstituted with highly purified syngeneic pluripotent hemopoietic stem cells. All types of thymus engraftment resulted in a restored T cell immunocompetence. The Tc reaction to Sendai virus in (B6 X bm1)F1 mice engrafted with both responder type B6 and nonresponder, type bm1 neonatal thymus allowed maturation of Sendai-specific, H-2Kb-restricted Tc. For the Tc reaction to H-Y, only responder type B6 thymus restored the Tc response, whereas this was not achieved with nonresponder type bm12 thymuses. We conclude from this study that in this radiation stem cell chimera system the radioresistant component of the thymus dictates major histocompatibility complex (MHC) specificity and immune response phenotype of T cells restricted to class II MHC molecules but not of T cells restricted to class I MHC molecules.

Fine specificity and T-cell receptor beta-chain gene rearrangements of five H-2Db-specific cytotoxic T-cell clones

A panel of cytotoxic T lymphocyte clones that recognize H-2b target cells has been established. Six different clones were distinguished according to the following criteria. First, the fine specificity of the clones was determined by testing proliferation and cytotoxicity on target cells of recombinant mice. Clone 221 recognized H-2Kb, and five other clones recognized H-2Db. Clone 433 distinguished itself from the other five Db-specific clones by cross-reacting with an antigen on H-2k cells. Second, the presence of an idiotypic determinant as defined by the 3F9 clone-specific monoclonal antibodies was investigated in cytotoxicity inhibition experiments. One of the Db-specific clones, 653, was inhibited by these antibodies and was therefore clearly different from the other Db-specific clones. The third criterion involved the rearrangement pattern of the DNA coding for the beta chain of the T-cell receptor. Southern blot analysis showed that each clone had a unique pattern. Interestingly, clone 653, which expresses the same idiotypic determinant as clone 3F9, had deleted the C beta 1 gene cluster, whereas this gene is functionally expressed in clone 3F9.

Characterization of virus-specific cytotoxic T cell clones from allogeneic bone marrow chimeras

We established several H-2-restricted lymphocytic choriomeningitis virus (LCMV)-specific cytotoxic T cell clones from spleens of virus-primed C57BL/6 or C57BL/10 (H-2b) and B10.BR (H-2k) mice and from allogeneic C57BL/10----B10.BR and B10.BR----C57BL/10 bone marrow chimeras. Two T cell clones of H-2b origin and restricted to H-2b, 3 of H-2k origin and restricted to H-2k were compared with two clones each derived from the two types of chimeras. Their surface phenotype was found to be Lyt-2+, L3/T4- and KJ16-133+ (2 of 9). Clones from chimeras expressed bone marrow donor H-2 and are restricted to the recipient H-2. H-2k-restricted clones were all specific for Kk whereas all H-2b-restricted clones were specific for Db. These restriction specificities could be further defined by the blocking activity of various monoclonal anti-H-2 antibodies. Interestingly the anti-H-2Db antibodies blocked the restricted virus-specific killing activity of the clones derived B10.BR----C57BL/10 chimeras much more effectively than the activity of the clones derived from conventional H-2b mice. The various clones differed with respect to their fine specificity for LCMV strains. The 3 clones of conventional B10.BR origin only recognized LCMV-WE but not LCMV-Armstrong, Aggressive or Docile; H-2b-restricted conventional clones recognized target cells infected with all LCMV strains except LCMV-UBC-Docile; the T cell clones from the bone marrow chimeras recognized with one exception all LCMV strains tested.

Induction of H-2-specific antibodies by injections of syngeneic Sendai virus-coated cells

The capacity of the B cell immunoglobulin receptor to recognize complexes of Sendai viral and H-2b antigens was investigated by studying the antibody response to injections of syngeneic Sendai virus-coated (SV+) spleen cells in C57BL/6 (B6) mice. Almost all mice produced alloreactive anti-H2 lymphocytotoxic antibodies. In contrast, such antibodies were found very exceptionally in mice injected with normal (SV-) cells or with Sendai virus (SV) only. The reaction pattern of the cytotoxic antibodies induced was variable and ranged from almost anti-private to widely cross-reactive serotypes. The results of reactions on H-2-congenic, -recombinant and -mutant mouse strains, and of capping and immunoprecipitation experiments showed that the cytotoxic antibodies were directed against H-2 class I molecules. The anti-H-2 antibodies exhibited enhanced binding for SV+ target cells, but absorption experiments showed that this was not the result of cross-reactions with cell surface Sendai viral determinants or with a molecular complex of H-2 plus SV. This conclusion was supported by the observation that syngeneic SV+ cells were not the predominant targets for the induced lymphocytotoxic antibodies. Our results do not support the existence of MHC-restricted antiviral antibodies, but show the induction of anti-class I H-2 alloantibodies by injections with syngeneic SV-coated cells. We present a model for regular induction of anti-H-2 antibodies without intentional alloimmunization.

Polymorphic and autoreactive H-2-specific monoclonal antibody isolated after injections of syngeneic Sendai virus-coated lymphocytes

An H-2-specific monoclonal antibody (mAb Q-1) was obtained from B10.Q (H-2q) mice injected with syngeneic Sendai virus-coated cells. The IgM monoclonal antibody recognizes the public determinant H-2.25 shared by H-2k (Kk) and H-2r haplotypes and cross-reacts with H-2d, H-2s, H-2p, and H-2q cells, the latter being the haplotype of the challenged B-cell donor. The binding of mAb Q-1 to H-2d, H-2s, H-2q, and H-2p cells was lower than to H-2k and H-2r and of decreasing affinity but could be clearly distinguished from the negative reactions with H-2b and H-2f cells. MAb Q-1 distinguishes between Sendai virus-coated and uncoated lymphocytes only cells with low-affinity binding. On virus-coated or infected (H-2p, H-2q, H-2d, H-2s) cells lysis was stronger than on normal lymphocytes. We interpret the enhanced lysis of Sendai virus-positive cells by mAb Q-1 to be due to recognition of a modified exposure of public H-2 determinants induced by Sendai virus.

Cooperation between cytotoxic and helper T lymphocytes in protection against lethal Sendai virus infection. Protection by T cells is MHC-restricted and MHC-regulated; a model for MHC-disease associations

The in vivo importance of class I MHC regulation of the Tc response to a natural pathogenic agent of high virulence was studied on the basis of our previous demonstration of a major difference in the capacity to generate a Sendai virus-specific Tc response between C57BL/6 (B6, H-2b) mice and H-2Kb mutant B6.C-H-2bm1 (bm 1) mice. These two mouse strains differ from each other only in three amino acids in the crucial H-2Kb restriction element for this response. bm 1 mice, in contrast to B6 mice, are Tc nonresponders against this virus, but show Sendai-specific T cell proliferation, antibody production, and DTH reactions, as well as NK cell activity, equal to those of B6 mice. B6, Sendai Tc-deficient bm 1 and T cell-deficient B6 nu/nu mice differ from each other in susceptibility to lethal pneumonia induced by i.n. inoculation of virulent Sendai virus. The lethal dose (LD50) in B6 mice averaged 152 TCID50, in bm 1 mice, 14 TCID50 and in B6 nu/nu mice 0.5 TCID50. The importance of Tc was also shown by the complete protection of B6 nu/nu mice against infection with a lethal virus dose by i.v. injection of a Sendai virus-specific, IL-2-dependent and H-2Kb-restricted B6 Tc clone. In vivo protection by this Tc clone was H-2Kb-restricted. Apart from Tc, an important role for virus-specific Th cells is evident from the difference in susceptibility between bm 1 and B6 nu/nu mice. This conclusion was supported by the demonstration that the mean survival time of B6 nu/nu and bm 1 nu/nu mice could be significantly prolonged, in an I-Ab-restricted manner, by the injection of in vitro-propagated, Sendai-specific B6 or bm 1 Th clones after a lethal dose of Sendai virus, and by the demonstration that inoculation of these Th clones provided help to virus-specific Tc by means of IL-2 production. Strikingly, Th and Tc cooperate in anti-Sendai virus immunity, since permanent survival of lethally infected nu/nu mice was only achieved by inoculation of a mixture of Tc and Th clones or a mixture of a Tc clone and rIL-2. This study provides a unique model for the study of MHC-disease associations.

Astrocytes as antigen-presenting cells. Part II: Unlike H-2K-dependent cytotoxic T cells, H-2Ia-restricted T cells are only stimulated in the presence of interferon-gamma

Various studies strongly suggest that astrocytes are potent immune-regulating cells. They can be activated to release prostaglandin E, interleukin-1- and interleukin-3-like factors. Cocultivation of antigen-specific T cell lines and astrocytes results in induction of Ia on astrocytes and antigen-specific proliferation of T cells. In the current study, astrocytes were found to be incapable of serving as stimulator cells when unprimed T lymphocytes were used as responders in syngeneic or allogeneic lymphocyte reactions. However, when interferon-gamma (IFN-gamma) was added, astrocytes became Ia positive and potent stimulators in both syngeneic or allogeneic lymphocyte responses. In the presence of IFN-gamma, astrocytes presented antigens to Ia-restricted T hybridoma cells; in contrast hapten was presented to Kb-restricted cytotoxic cloned T cells by astrocytes in the absence of IFN-gamma. Thus, cultured astrocytes do function directly as accessory cells in class I antigen-dependent T cell activation, whereas Ia induction by IFN-gamma is necessary to enable them to present antigen to class II antigen-restricted T cells.

Human thymocyte maturation in vitro: a flow cytometric analysis

Using an in vitro culture system, light scatter analyses, and two-color flow cytometry, we provide evidence that the interleukin-2 (IL-2) and transferrin receptors can be induced within 48 hr on nonproliferating immature thymocytes. The thymocytes (greater than 35%) that expressed the transferrin and IL-2 receptors demonstrated nuclear activation as measured by log 90 degrees light scatter analysis. Increases in antigen-receptor-associated T3-antigen expression followed transferrin and IL-2-receptor induction and occurred on maximally activated T4+T8+ thymocytes on Day 3 of culture. Maximal T3 expression did not occur until Days 5-7 and paralleled loss of T4, T8 coexpression, suggesting an association between a mature T3-Ti antigen receptor complex and a mature T4, T8 phenotype.

Induction or prevention of immunopathological disease by cloned cytotoxic T cell lines specific for lymphocytic choriomeningitis virus

Cloned lymphocytic choriomeningitis virus (LCMV)-specific cytotoxic T lymphocyte (CTL) lines were prepared from spleens of 129/J (H-2b) mice immunized 7-9 months earlier with LCMV (UBC strain), or of C57BL/10J (H-2b) mice immunized 4 to 5 weeks earlier with LCMV (Armstrong strain). One uncloned and 3 cloned cytotoxic T cell lines were assessed for their respective abilities to produce, or protect against, fatal disease upon transfer to appropriate recipients or to induce specific footpad-swelling reaction. The effects of all lines were essentially identical. In recipient mice acutely infected with LCMV and immunosuppressed either by irradiation (750-990 rds) or treatment with cyclophosphamide, cloned T cells administered intracerebrally (i.c.) caused a convulsive disease and death within 1-4 days. No disease was produced when the same CTL were transferred to uninfected recipients or when they had been frozen and thawed prior to transfer to infected recipients. When admixed with 500 plaque-forming units of LCMV and transferred i.c. to immunocompetent H-2b mice, the T cell clones prevented overt disease. Allogeneic (H-2k) recipients of this same admixture all developed typical LCM disease as did H-2b recipients of the admixture after T cells had been frozen and thawed. Inoculation of cloned CTL into preinfected footpads induced a specific footpad-swelling reaction, which reached maximum levels after about 36 h. Irradiated and infected recipients of cloned LCMV-specific T cells showed the footpad-swelling reaction only when they had been reconstituted with bone marrow cells. In contrast, cloned T cells induced LCM disease in i.c. infected and irradiated mice independent of bone marrow reconstitution. These findings indicate that both fatal LCMV-induced neurologic disease and protection against it are mediated directly by virus-specific CTL.