The self determinants recognized by human virus-immune T cells can be distinguished from the serologically defined HLA antigens

The self specificity of human influenza virus-immune cytotoxic T cells has been analyzed in order to clarify the relationship between the self antigens that they recognize and the serologically defined HLA-A and -B antigens. Virus-immune effectors from HLA-A2-positive donors were tested on panels of virus-infected target cells from donors who were either HLA-mismatched or matched only for HLA-A2. Virus-immune T cells from 11 out of 11 A2-positive donors lysed all A2-matched virus-infected target cells (and no HLA-mismatched targets), except that each of these effector cells consistently failed to lyse virus-infected target cells from one A2-positive donor (designated M7). Although the A2 specificity of donor M7 could also be distinguished from the A2 antigen of other donors by alloimmune cytotoxic T cells, no differences in the A2 antigen of donor M7 could be defined by extensive serologic analyses. These results indicate that there is a strong but incomplete association between a self antigen recognized by virus-immune T cells and the serologically defined HLA-A2 specificity.     

Virus specificity of human influenza virus-immune cytotoxic T cells.

The virus specificity of human in vitro cytotoxic T cell responses to influenza virus was studied with the use of peripheral blood mononuclear leukocytes from normal adult volunteers. Previous natural exposure of these donors to a variety of type A influenza viruses was documented by HI antibody titers. Cells sensitized in vitro with A/HK or A/PR8 were cytotoxic for autologous target cells infected with A/HK, A/PR8, or A/JAP 305 type A influenza viruses, but not for B/HK-infected or uninfected cells. B/HK-sensitized effector cells lysed target cells infected with B/HK but not targets infected with type A viruses. A/HK- and A/PR8-immune effector populations were shown to recognize cross-reactive antigens on A/HK- and A/PR8-infected target cells by cold target competition. Influenza-immune effector cells were cytotoxic for virus-infected autologous targets but much less so for virus-infected allogeneic targets. This self-restriction suggested that the cytotoxicity was largely T cell-mediated and was confirmed by cell separation analysis. Thus, the human secondary cytotoxic T cell response in vitro to influenza viruses is predominantly directed against cross-reactive determinants on cells infected with serologically distinct type A influenza viruses.     

Differences in HLA antigen recognition by human influenza virus-immune cytotoxic T cells.

The specificity of in vitro induced human influenza-immune cytotoxic effector cells was analyzed with respect to recognition of HLA-A and -B-linked gene products. The influenza-immune cytotoxic activity observed on panels of virus-infected targets demonstrated that virus-immune effectors preferentially lyse targets with which they share HLA-A or -B specificities. Virus-immune effectors from certain donors recognized virus in conjunction with some, but not all, of their self HLA-A and -B antigens. Among donors who share a given HLA antigen (such as A2 or B7), there are differences in the ability of their virus-immune T cells to recognize the shared antigen. Virus-infected target cells from HLA-A2 or -B7 "nonresponder" donors could be lysed by virus-immune T cells obtained from other donors who shared only the HLA-A2 or -B7 antigen with these target cells. These observations suggest that the absence of cytotoxic T cell responses by some donors to influenza virus in conjunction with HLA-A2 or -B7 is not due to control by the structural genes that code for these HLA antigens, but rather may result from control by regulatory genes that act at the level of the responder and/or stimulator cell. The results are discussed in the context of Ir gene regulation of human T cell responses.     

Differential effect of hybrid resistance on the localization of virus-immune effector T cells to spleen and brain

The hybrid resistance (Hr) effect operates in the lymphocytic choriomeningitis (LCM) in vivo transfer model to inhibit both the level of cytotoxicity T lymphocyte (CTL) generation in spleen and the induction of inflammation in cerebrospinal fluid (CSF). The effect is seen when LCM virus-immune T cells that are homozygous for H-2D ^b are injected into virus-infected, immunosuppressed recipients that are heterozygous for this allele, or into radiation chimeras that express an appropriate F₁ phenotype. Evidence that Hr to T -cell transfer is cell-dose-dependent and tends to diminish with age was found in both chimeric and normal F₁ mice. Inhibition of the capacity of injected T cells to cause meningitis is a more sensitive measure of Hr than is the further stimulation of CTL effectors in recipient lymphoid tissue. The injection of large numbers of H-2^b virus-immune T cells into (H-2 ^k X H-2 ^bF₁H-2 ^k) virus-infected recipients did not induce any cellular extravasation into CSF, though potent H-2^b-restricted CTL effectors were generated in recipient spleen. Evidence of minimal inflammatory process was found in one experiment where these chimeras were given a comparable dose of (H-2 ^b X H-2 ^d)F₁ immune spleen cells. Development of this Tcell-mediated immunopathological process depends essentially on the expression of the appropriate H-2 restriction element on radiation-resistant host cells which, in this case, presumably constitute part of the physiological barrier between blood and CSF.     

Antigen-specific human T lymphocyte clones: viral antigen specificity of influenza virus-immune clones

Human T lymphocyte clones (TLC) specific for type A (A/Texas/1/77) influenza virus and maintained in continuous culture with T cell growth factor, were analyzed to define the cellular specificity pattern of virus recognition. A panel of TLC were stimulated with strains of serologically characterized type A influenza subtypes. Five TLC recognized all the viral subtypes; the remaining clones recognized only subtypes that shared serologically defined determinants with the immunizing subtype. In addition, the 11 TLC were analyzed for their fine antigenic specificity by using the purified viral components hemagglutinin (HA), neuraminidase (NA), matrix protein (MP), and nucleoprotein (NP). Five TLC proliferated in response to NA, four to MP, one to HA, and one to NP. None of the clones responded to the unrelated B strain influenza virus, B/Singapore. Furthermore, the fine specificity of an MP-reactive TLC was confirmed by subcloning.     

Receptor sensitivity: when T cells lose their sense of self

The T-cell antigen receptor binds to self-MHC molecules with low affinity. Recent reports disagree as to whether this interaction sensitizes or desensitizes the receptor. Here we discuss how these findings might be reconciled.     

Recognition of self and altered self by T cells in autoimmunity and allergy

T cell recognition of foreign peptide antigen and tolerance to self peptides is key to the proper function of the immune system. Usually, in the thymus T cells that recognize self MHC+ self peptides are deleted and those with the potential to recognize self MHC+ foreign peptides are selected to mature. However there are exceptions to these rules. Autoimmunity and allergy are two of the most common immune diseases that can be related to recognition of self. Many genes work together to lead to autoimmunity. Of those, particular MHC alleles are the most strongly associated, reflecting the key importance of MHC presentation of self peptides in autoimmunity. T cells specific for combinations of self MHC and self peptides may escape thymus deletion, and thus be able to drive autoimmunity, for several reasons: the relevant self peptide may be presented at low abundance in the thymus but at high level in particular peripheral tissues; the relevant self peptide may bind to MHC in an unusual register, not present in the thymus but apparent elsewhere; finally the relevant self peptide may be post translationally modified in a tissue specific fashion. In some types of allergy, the peptide+ MHC combination may also be fully derived from self. However the combination in question may be modified by the presence of other ligands, such as small drug molecules or metal ions. Thus these types of allergies may act like the post translationally modified peptides involved some types of autoimmunity.     

Health as intra-systemic integrity: rethinking the foundations of systems biology and nanomedicine

In current research on systems biology and nanomedicine, we often find an ideal of a new science-based preventive medicine. I consider how disease, cause, explanation, diagnosis, and treatment are understood within this ideal, with special attention to the role of nanoscience and technology in elucidating the "circuit diagram" of a healthy system. I argue that the developmental systems theory that informed George Engel's biopsychosocial model addresses some deficiencies in the current systems ideal, but it needs to be integrated with an ethical analysis that is more attentive to the socioeconomic, cultural, and institutional factors that condition how we understand and manage disease. We also need a richer account of top-down causal paths if we are to appropriately understand diseases as disruptions of inter- and intra-systemic integrity.     

Studies on T helper cells and the specificity of their soluble products for induction of cytotoxic T cells directed against trinitrophenyl-modified self

The role of T helper cells (Th) and their soluble products in the generation of a cytotoxic T-cell (CTL) response of thymocytes to trinitrophenyl (TNP)-modified syngeneic cells was investigated. The Th have a Thy 1⁺ Lyt 1⁺2^? surface phenotype, and produce at least two soluble helper factors. Production of factors requires stimulation of primed Th by specific antigen (self-TNP), and depends on a Thy 1⁺ Lyt 1⁺2^? cell. Factors present in supernatants after 5 hr of stimulation act preferentially on antiallogeneic precursor CTL (pCTL); factors present at 24 hr act preferentially on self-TNP-specific pCTL with a variable activity for alloantigen-specific pCTL. These results are interpreted as suggesting a possible role for helper factors having selective action in generation of CTL responses.     

Projection of an immunological self shadow to developing T cells via macroautophagy

Due to a production error, a mistake has been introduced in the contents page in the print version of the November issue. The corrected title and author information of the second Research Highlight is as follows：     

Antigen-specific human T lymphocyte clones: induction, antigen specificity, and MHC restriction of influenza virus-immune clones

Human peripheral blood lymphocytes from an HLA-Dw1,3 individual were primed in vitro with influenza A virus (A/Texas/1-77/x-49) and subsequently cloned by limiting dilution in TCGF. Of the 96 TLCs originally obtained, nine were characterized in detail. TLCs were antigen specific, responding to influenza A virus, not to influenza B, TGAL, GAT, tetanus toxoid, or KLH, and only when antigen was presented by cells unable to form rosettes with AET-treated SRBC. Presentation of antigen by unseparated PBL often resulted in significant "back stimulation," probably via production of growth factors. The MHC requirements for the induction of TLC proliferation were analyzed. Of four representative clones analyzed, three required Dw1;DR1 compatibility for successful presentation of viral antigens by a panel of antigen-presenting cells. In contrast, one TLC showed an unusual pattern of response that could not be correlated to a particular HLA haplotype. Monoclonal anti-T cell antibody analysis of the surface phenotype of two TLCs maintained in continuous culture for 5 mo indicated that they were OKT3+, 4+, and 8-, consistent with an inducer/helper phenotype. To confirm the clonal nature of TLCs, data on the functional properties of TLC subclones are also presented.     

Recognition of the self idiotype by T cells: induction of a rapid increase in cytoplasmic free calcium in T cells recognizing a variable L chain determinant.

To investigate the initial stages of recognition of the self idiotype (Id) by T cells, we examined the early increase in cytoplasmic free calcium ([Ca2+]i) occurring in murine CD4+ T cells specific for a model Id, Id315, following their interaction with the Id. The changes in [Ca2+]i were monitored with stopped-flow fluorometry by loading T cells with fura 2, a Ca(2+)-binding fluorescent dye. An increase of [Ca2+]i in the Id-specific T cell line was dependent on the presence of both antigen-presenting cells (APC) and Id315. When T cells were mixed with APC pulsed with M315 for 90 min at 37 C, a significant increase in T cell [Ca2+]i was observed within one second. A pronounced elevation in [Ca2+]i was also observed in T cells after their interaction with APC which had been pulsed for 90 min with VL-315 Id-containing proteins (such as VL-315, L315, Fv-315 or Fab'-315 fragments). In contrast, pulsing APC for 5 min with the VL fragment produced little or no change in the [Ca2+]i. These results suggest that VL must be further processed by APC before it can be recognized by T cells. Indeed, a synthetic VL region peptide (positions 91-108, designated as P18) produced an elevation in T cell [Ca2+]i when mixed with APC without pulsing.     

Anti-tumor activity and trafficking of self, tumor-specific T cells against tumors located in the brain

It is commonly believed that T cells have difficulty reaching tumors located in the brain due to the presumed "immune privilege" of the central nervous system (CNS). Therefore, we studied the biodistribution and anti-tumor activity of adoptively transferred T cells specific for an endogenous tumor-associated antigen (TAA), gp100, expressed by tumors implanted in the brain. Mice with pre-established intracranial (i.c.) tumors underwent total body irradiation (TBI) to induce transient lymphopenia, followed by the adoptive transfer of gp100(25-33)-specific CD8+ T cells (Pmel-1). Pmel-1 cells were transduced to express the bioluminescent imaging (BLI) gene luciferase. Following adoptive transfer, recipient mice were vaccinated with hgp100(25-33) peptide-pulsed dendritic cells (hgp100(25-33)/DC) and systemic interleukin 2 (IL-2). This treatment regimen resulted in significant reduction in tumor size and extended survival. Imaging of T cell trafficking demonstrated early accumulation of transduced T cells in lymph nodes draining the hgp100(25-33)/DC vaccination sites, the spleen and the cervical lymph nodes draining the CNS tumor. Subsequently, transduced T cells accumulated in the bone marrow and brain tumor. BLI could also detect significant differences in the expansion of gp100-specific CD8+ T cells in the treatment group compared with mice that did not receive either DC vaccination or IL-2. These differences in BLI correlated with the differences seen both in survival and tumor infiltrating lymphocytes (TIL). These studies demonstrate that peripheral tolerance to endogenous TAA can be overcome to treat tumors in the brain and suggest a novel trafficking paradigm for the homing of tumor-specific T cells that target CNS tumors.     

Immunologic self tolerance maintained by T-cell-mediated control of self-reactive T cells: implications for autoimmunity and tumor immunity

T-cell-mediated dominant control of self-reactive T cells is one mechanism for maintaining immunologic self tolerance. It also hampers the generation of immunity to autologous tumor cells. Abrogation of the control can evoke potent tumor immunity as well as autoimmunity in normal animals. This common regulatory mechanism for autoimmunity and tumor immunity can be exploited to devise a novel immunotherapy against cancer.     

Characterization of two suppressor cells that together prevent in vivo development of cytolytic T cells to hapten-altered self

Two suppressor cell populations that interact to down-regulate in vivo development of the cytolytic T-cell (CTL) response to trinitrophenyl-modified syngeneic spleen cells (TNP-SC) have been further characterized. Suppressor cells induced by the iv injection of trinitrophenyl-modified syngeneic spleen cells possess Thy 1.2 antigen. Their precursors are insensitive to pretreatment of host animals with cyclophosphamide (CY). Suppressor cells that arise after dermal sensitization with trinitrochlorobenzene are also Thy 1.2 antigen positive but their precursors are sensitive to pretreatment with CY. These characteristics of the two suppressor T cells (Ts) are identical to those of the two Ts that are generated by similar methodologies and that together suppress contact sensitivity (CS) to picryl chloride. Neither the CS nor CTL response was suppressed when host animals possessed only one set of Ts. In contrast to suppression of CS at the efferent phase, development of CTL was suppressed only when the two Ts were present early during sensitization (afferent phase). Since the results point to several similarities between the two sets of Ts that are active in the down-regulation of the CS and CTL responses, it is suggested that the two dissimilar immune responses directed to the same hapten, namely CS and CTL, may be controlled by the same suppressor cells. Since it appears that the two sets of Ts interact to affect different phases of the CS and CTL responses, down-regulation of each must be accomplished through different mechanisms.     

Survival and homeostatic proliferation of naive peripheral CD4+ T cells in the absence of self peptide:MHC complexes

TCR-self peptide:MHC interactions play a critical role in thymic positive selection, yet relatively little is known of their function in the periphery. It has been suggested that continued contact with selecting MHC molecules is necessary for long-term peripheral maintenance of naive T cells. More recent studies have also demonstrated a role for specific self peptide:MHC complexes in the homeostatic expansion of naive T cells in lymphopenic mice. Our examination of these processes revealed that, whereas self class II MHC molecules do have a modest effect on long-term survival of individual CD4+ T cells, interactions with specific TCR ligands are not required for peripheral naive CD4+ T cell maintenance. In contrast, selective engagement of TCRs by self-peptide:MHC complexes does promote proliferation of CD4+ T cells under severe lymphopenic conditions, and this division is associated with an activation marker phenotype that is different from that induced by antigenic stimulation. Importantly, however, the ability of naive T cells to divide in response to homeostatic stimuli does not appear to be stringently dependent on TCR-self peptide:MHC interactions. Therefore, these results show that the factors regulating survival and homeostatic expansion of naive T cells in the periphery are not identical. In addition, we provide evidence for a novel form of T cell proliferation that can occur independently of TCR signaling and suggest that this reflects another mechanism regulating homeostatic T cell expansion.     

Helper cells in the autologous mixed lymphocyte reaction. I. Generation of cytotoxic T cells recognizing modified self H-2

The autologous mixed lymphocyte reaction (AMLR) in mice measures the proliferative response of T cells to determinants on syngeneic non-T spleen cells. Normally, cytotoxic T lymphocytes (CTL) are not generated in this reaction. However, the addition of trinitrophenyl-modified mitomycin C-treated syngeneic T cells (TNP-Tm) to the AMLR results in the generation of TNP-specific CTL but does not alter the proliferative response. Significant cytotoxic activity is not detectable against TNP in association with Ia unless TNP is present on cells bearing those determinants. Thus, if unselected spleen cells are TNP-modified and used as stimulators in the AMLR, the proliferative response is enhanced and CTL are generated that recognize TNP in association with K, D, and I region-encoded determinants. The CTL generated in the AMLR are H-2 restricted and dependent on the presence of adherent cells in the sensitization cultures. The experiments presented here suggest that the AMLR can provide the help necessary for generating cytotoxic T cells in vitro.