The role of the human major histocompatibility complex in cytotoxic T-cell responses to virus-infected cells

The full length genomic sequence of a novel HLA-A*24 allele, HLA-A*24:353, identified in a patient with hepatitis B infection

HLA-A*24:353 differs from HLA-A*24:02:01 by an amino acid exchange glutamine to glutamate at position 316.

Pathogenic and protective correlates of T cell proliferation in AIDS. HNRC Group. HIV Neurobehavioral Research Center

To investigate the association of antigen specific CD4 T cell activation with HIV disease progression and AIDS-related central nervous system damage, T cell proliferation responses to HIV, CMV, and HSV were evaluated in infected individuals. CD4 T cell loss and neurocognitive impairment were assessed at 6-mo intervals. Individuals with known times of seroconversion who responded to more HIV peptides were at greater risk of progressing to < 200 CD4 T cells (P = 0.04) and dying (P = 0.03) than those with responses to fewer peptides. A positive correlation (0.52) was seen between the breadth of the HIV proliferation response and HIV plasma RNA levels. Higher proliferation responses to CMV and HSV were also associated with more rapid CD4 loss (P = 0.05). HLA phenotyped individuals (n = 150) with two HLA-DR alleles associated with response to more HIV peptides and CMV (DR-2,5,w6,10) were less likely to develop neurocognitive (P = 0.002) and neurologic impairment (P = 0.04), but were not protected from CD4 loss and death. Thus, the ability to generate a greater T cell proliferation response to HIV and opportunistic herpes viruses may lead to resistance to central nervous system damage, but also risk of more rapid HIV disease progression.

Adult human glial cells can present target antigens to HLA-restricted cytotoxic T-cells

T-lymphocyte recognition of antigen either on antigen-presenting cells (APC) necessary for the generation of an immune response or on target cells during the effector phase of a cellular immune response requires expression of HLA molecules. Although immune mechanisms operate in many disease processes of the central nervous system (CNS), cells of the CNS generally express low levels of HLA molecules. In this study, the potential for upregulation of HLA molecules on adult human glial cells was examined. Moreover, the functional implication of this upregulation was assessed by the capacity of glial cells to process and present target antigens to HLA class I-restricted influenza-specific and class II-restricted myelin basic protein (MBP)-specific CTL lines. Glial cells cultured from adult human surgical brain specimens or cells from established glioblastoma multiforme cell lines were studied. Lysis by antigen-specific CTLs was dependent on treatment of the target cell with interferon-gamma. The lysis was HLA restricted and antigen specific. The results indicate that adult human glial cells can process and present antigen to HLA-restricted CTLs but require the upregulation of HLA molecules. These findings have implications for infectious and autoimmune diseases of the CNS.

Impaired human leukocyte antigen-restricted measles virus-specific cytotoxic T-cell response in subacute sclerosing panencephalitis

The capacity of peripheral blood lymphocytes to proliferate in response to measles virus and to generate measles virus-specific cytotoxic T lymphocytes (CTL) was examined in 4 patients with subacute sclerosing panencephalitis (SSPE). The lymphoproliferative response to measles virus was obtainable in the 4 SSPE patients. In contrast, the CTL response to measles virus was reduced in 3 of the 4 SSPE patients. This defect appeared to be in the generation of the measles virus-specific CTLs, since measles virus-infected target cells from the patients could be lysed by human leukocyte antigen-matched peripheral blood lymphocytes from healthy individuals. The SSPE patients with reduced measles virus CTL response had a normal ability to generate mumps virus, influenza virus, or alloantigen-specific CTLs. The lysis of measles virus-infected targets that was observed with these SSPE patients could be reduced by depleting the effectors of natural killer cells or by performing cold target blocking with K562 cells, indicating that the lysis of the measles virus-infected targets was probably mediated by natural killer cells. These results demonstrate a reduction in the cell-mediated immune response to measles virus as measured by the generation of measles virus-specific CTLs in 3 of the 4 SSPE patients studied. This defect could relate to the persistence of measles virus in these patients.

Phenotypic heterogeneity of cerebrospinal fluid-derived HIV-specific and HLA-restricted cytotoxic T-cell clones

A variety of clinical syndromes, including AIDS and neurological disorders, may follow as a consequence of infection with the human immunodeficiency virus type 1 (HIV-1). It is not yet clear, however, to what extent the destruction of lymphocytes and neural cells associated with these conditions is caused by adverse immune responses to HIV-1 or how much is due to cytopathic effects of the virus itself. Here we document the existence of HLA-restricted, HIV-1-specific cytotoxic T lymphocytes in the cerebrospinal fluid of two AIDS patients manifesting neurologic disorders. These cytotoxic T lymphocytes showed dual specificity, recognizing target cells coated with purified HIV-1 envelope glycoprotein (gp 120) or inactivated HIV-1 in the context of HLA antigens. Cytotoxic T-cell clones derived from one of the AIDS patients revealed restriction specificities representing both HLA class I and HLA class II antigens. Considerable phenotypic heterogeneity was observed amongst these clones, some expressing conventional combinations of cytotoxic T-cell surface markers, and others displaying unusual phenotypes. The presence of HIV-specific cytotoxic T lymphocytes in AIDS patients, and in particular in their cerebrospinal fluid, suggests that these cytotoxic effectors may participate in the lymphoid cell and/or neurologic damage observed in such patients.

Human T4+ T-lymphocyte clones specific for the B fragment of tetanus toxin

Two T4+ cloned T-lymphocyte lines specific for a papain digest product of tetanus toxin are functionally characterized. The two clones were obtained from peripheral blood mononuclear cells activated in vitro by tetanus toxoid, expanded with IL-2, and cloned in soft agar. Both clones could be induced to undergo blastogenesis with tetanus toxoid, tetanus toxin, and the B fragment but not the C fragment of tetanus toxin. In addition, both clones caused cytolysis of plastic adherent cell targets cocultured for 18 hr with either tetanus or the B fragment. Antigen specific proliferation and cytolytic activity were MHC-class I restricted.

Human mumps virus-specific cytotoxic T lymphocytes: quantitative analysis of HLA restriction

To obtain quantitative information about the use of HLA antigens as restriction element by antiviral cytotoxic T lymphocytes (CTL), we have analyzed precursors of human mumps virus-specific CTL by limiting dilution. CTL generated by restimulation of peripheral blood T lymphocytes with autologous mumps virus (MV)-infected stimulator cells were restricted by autologous HLA class I antigens, and derived from the T4-8+ population. They were specific for MV and did not lyse autologous target cells infected with other viruses. Frequencies of MV-specific CTL precursors ranged from 1/500 to 1/8000. HLA restriction was analyzed by split-well analysis of individual CTL colonies. CTL recognizing HLA-A or B antigens were unequally distributed: HLA-B7, -B13, and -B27 were found to function as predominant, in some cases as exclusive, restriction elements, whereas other antigens such as HLA-A24 were never or rarely used. In several combinations, there was no evidence for antigenic variants of HLA molecules as reason for the failure to be recognized. The proportion of CTL precursors recognizing HLA-A2 and -B8 seemed to be dependent on the presence or absence of "dominant" restriction elements. We conclude that CTL precursors recognizing certain virus-HLA combinations are preferentially expanded during an infection, but that low responsiveness to a given combination is not necessarily absolute.

Induction of measles virus-specific human cytotoxic T cells by purified measles virus nucleocapsid and hemagglutinin polypeptides

The measles virus polypeptide specificity of human measles virus-specific, HLA class II restricted cytotoxic T cells have been examined. Measles virus-specific CTL have been generated using purified measles virus nucleocapsid and hemagglutinin polypeptides during a primary, in vitro stimulation of bulk cultures. Both the purified preparations of measles virus nucleocapsid and hemagglutinin polypeptides were effective in stimulating a measles virus-specific CTL response. The measles virus nucleocapsid-induced CTL response could be blocked by an anti-HLA class II monoclonal antibody but not an anti-HLA class I antiserum. Moreover, considerably less measles virus nucleocapsid was required to stimulate a comparable CTL response than the measles virus hemagglutinin which suggests that the CTL response to measles virus may be skewed towards internal viral determinants of measles virus. These studies indicate that both internal and external components of measles virus are effective in inducing measles virus-specific CTL. The recognition of internal viral components may represent an important part of the T cell mediated immune response to viruses.

The role of IL-2 and T4+ cells in the generation of human influenza virus-specific CTL activity

Stimulation of human peripheral blood lymphocytes (PBL) with influenza A virus leads to the generation of virus-specific cytotoxic T lymphocyte (CTL) activity as well as natural killer (NK)-like activity. In this study, we show that exogenous IL-2 augments the in vitro generation of virus-specific CTL activity, only when added some days after the initiation of the culture. Apparently, the endogenously produced IL-2 can be a limiting factor in the in vitro generation of CTL activity. The increase of influenza virus-specific CTL activity after addition of exogenous IL-2 does not affect the restriction pattern of the CTL response. So, the preferential use of certain HLA antigens as restriction elements is not due to a limiting amount of endogenously produced IL-2. Depletion of T4+ cells completely abrogates the generation of virus-specific CTL activity. Addition of exogenous IL-2 to T4+-cell-depleted cultures fully restores the generation of HLA-restricted virus-specific CTL activity. We conclude that in the in vitro generation of virus-specific CTL activity in bulk cultures of human PBL the sole function of T4+ cells in human virus-specific CTL generation is the production of IL-2, no cognitive cell interaction of T8+ CTL precursors with T4+ cells is required, and in bulk cultures T8+ cells themselves are not able to produce sufficient amounts of IL-2 to ascertain the maturation of virus-specific CTL precursors into cytolytic T cells. Finally, we show that exogenous IL-2 also has a stimulatory effect on the NK-like or lymphokine-activated killer activity, which is always concomitantly induced in virus-specific CTL generation cultures, but has no influence on the levels of IFN produced in such cultures.

The proliferative immune response to autologous Epstein-Barr virus transformed lymphoblastoid cells. II. Studies with HLA class II loss variants demonstrate a role for gene products other than DR and DQ

The Epstein-Barr virus (EBV) transformed lymphoblastoid cell line (LCL-721) and some of its HLA loss mutant derivatives were used to study the immune specificity of the autologous proliferative T cell response to antigens expressed as a result of EBV infection. We have measured secondary and tertiary proliferative responses to well-characterized variants that lack expression of some or all known class II gene products (DR, DQ, and DP). These experiments prove that the region mapping between DR/DQ and glyoxalase I (GLO) of one haplotype controls at least one specific restriction element which is recognized in the autologous response to LCL-721. Furthermore, specific proliferative responses to variants lacking expression of all known class II gene products indicate the recognition of determinants other than DR, DQ, and DP.

A human helper-dependent influenza virus-specific cytotoxic T lymphocyte clone restricted by HLA-DR2

A human influenza A virus-specific cytotoxic T lymphocyte (CTL) clone is described that is restricted by a class II HLA-antigen. Of a large panel of B-lymphoblastoid cell lines (B-LCL) as target cells the clone lysed only infected cells sharing HLA-DR2 with the donor of the clone. In cold target inhibition studies only infected cells bearing HLA-DR2 could inhibit cytotoxicity. Infected PHA-blasts that express less DR-antigen than B-LCL cells were lysed to a much lesser extent though they could be infected equally well. Trypan blue staining and postlabelling of the target cells showed that the clone indeed killed the target cells. The clone did not proliferate in response to infected irradiated autologous LCL cells and had the OKT3+4+8-DR+ phenotype. The possible significance of class II restricted CTL is discussed.

The proliferative immune response to autologous Epstein-Barr virus-transformed lymphoblastoid cells. I. Studies with HLA haplotype loss variants demonstrate a role for MHC-linked genes

The human Epstein-Barr virus transformed lymphoblastoid cell line (EBV-LCL) 721 and MHC haplotype loss variants derived from it were utilized to dissect the functional role of MHC genes in the proliferative response of autologous T lymphocytes to EBV-LCL. LCL-721 is heterozygous at all phenotypically defined MHC loci. One type of LCL-721 variant expresses only determinants encoded by the maternal (m) haplotype and the other expresses determinants encoded by the paternal (p) haplotype. Autologous (individual A) primary proliferative responses are strong to each type of haplotype deletant. The strong tertiary responses to the priming haplotype in comparison to the relatively weak responses to the reciprocal haplotype indicate that MHC linked genes encoded by each haplotype are important in the autologous response to EBV-LCL. Similar specific tertiary responses are observed when peripheral blood lymphocytes (PBLs) from the donor's mother are used as responding cells. Allogeneic responses were also studied by priming PBLs from unrelated donors with the haplotype deletants. Quantitative comparisons of the proliferation by primed allogeneic and autologous lymphocytes stimulated by irradiated PBLs from donor A and her mother, and by LCL-721 and its variants, show that some of the tertiary responses involve specific recognition of EBV-LCL while others detect recognition of alloantigens.

Autologous mixed lymphocyte reaction in man: XV. Cellular and molecular basis of deficient autologous mixed lymphocyte response in insulin-dependent diabetes mellitus

The autologous mixed lymphocyte response (AMLR) and the allogeneic mixed lymphocyte response were deficient in a subset of patients with newly diagnosed insulin-dependent diabetes mellitus (IDDM). Using a single set of HLA-identical twins, the cellular and molecular basis of deficient AMLR was investigated and appears to be due to a defect in both responder T cells and stimulator non-T cells. Interleukin-2 production was diminished in the patient but not in the healthy twin. The in vitro addition of purified interleukin-2 enhanced the depressed AMLR in the diseased twin. This suggests that the deficient AMLR in IDDM may be in part due to a deficiency in the production of interleukin-2.

Functional T lymphocyte immune deficiency in a population of homosexual men who do not exhibit symptoms of acquired immune deficiency syndrome

To determine whether healthy homosexual men are immunologically impaired, peripheral blood leukocytes (PBL) from 20 male homosexuals were compared prospectively with PBL from 14 age-matched male heterosexual donors with respect to: (a) the capacity of their PBL to generate functional T cell immune responses in vitro; and (b) the content of total T cells and T cell subsets in their peripheral blood. The homosexual donors studied indicated moderate sexual life styles in that all but one of the donors had less than five current sexual partners. The percentages of OKT3+, OKT4+, and OKT8+ T cells were similar to those of heterosexual controls. T cell function was assessed by measuring cytotoxic T cell responses to influenza virus and to allogeneic cells. Approximately one-third of the homosexual donors consistently exhibited weak cytotoxic T lymphocyte (CTL) responses to influenza virus, whereas all of the heterosexual donors generated strong CTL responses to influenza. There was no correlation between the strength of CTL responsiveness to influenza virus and the strength of CTL responses to allogeneic cells. These results suggest that the influenza-specific CTL response may be a sensitive indicator of immunologic defects in asymptomatic homosexuals. If acquired immune deficiency syndrome results from an infectious agent, it remains to be seen if such immunosuppression predisposes to the infection, or if it reflects early consequences of infection.

Distinct epitopes on the T8 molecule are differentially involved in cytotoxic T cell function

The present report attempts to determine if there are distinct epitopes on the T8 molecule that are involved in class I-restricted cytotoxic T lymphocyte (CTL) function. A panel of 9 monoclonal antibodies (OKT8A,B,C,E,F,G,H,I, and OKT5) was produced and all antibodies were shown to bind to the T8 molecule. This panel of antibodies was employed to characterize the distribution of distinct epitopes on the T8 molecule and to block the activity of class I-specific influenza virus-immune and allo-immune CTL effector function. Significant differences in the ability of the anti-T8 antibodies to block CTL function were observed: OKT8C and T8F blocked best (49 and 55% respectively); OKT8A,E,G,H,I, and OKT5 blocked less well (24-31%); and OKT8B blocked marginally (11%). There was no correlation between the capacity of the antibodies to block CTL function and their heavy chain isotype. Competitive binding of the different OKT8 antibodies to the cell surface and differential trypsin sensitivity of the epitopes recognized by the antibodies indicated that OKT8C and T8F were located on topographically distinct regions of the T8 molecule. These results indicate that specific epitopes on the T8 molecule are involved in CTL function, and that there could be more than one functional site on the molecule.

Interaction of microbial agents with the immune system during infectious disease

Research during the last years has revealed a considerable complexity of the immune system. It is clear that immunological reactions depend on extensive and only partly clarified interactions between a number of different cell types (e.g. B lymphocytes, plasma cells, T cell subpopulations, cytotoxic K and NK cells, monocytic cells, neutrophilic and eosinophilic granulocytes) and their molecular products (e.g. immunoglobulins, lymphokines and interleukins). These components further interact with the complement system, as well as with immunologically nonspecific components like acute phase proteins (e.g. C-reactive protein) and with other pathophysiological phenomena occurring during infections, e.g. the fever response. The application of these observations from basic and experimental immunology to the investigation of antimicrobial immune reactions is still only in its beginning, but has already resulted in new concepts of clinical value for the understanding of infectious diseases. The present paper briefly describes certain aspects of the immune response to infections with various microbial agents, with particular emphasis on reactions of clinical importance. In addition to B and T cell reactions, possible antimicrobial functions of K cells and NK cells are discussed, and the possible importance in infectious disease of various T cell subpopulations, particularly T suppressor cells, is discussed. Lastly, various escape mechanisms are mentioned whereby certain microbial agents may evade elimination by the immune response of the host.

Interleukin-2 enhances the depressed natural killer and cytomegalovirus-specific cytotoxic activities of lymphocytes from patients with the acquired immune deficiency syndrome

The recently described acquired immune deficiency syndrome (AIDS) is characterized by the occurrence of severe opportunistic infections and an aggressive form of Kaposi's sarcoma. A variety of profound defects in cell-mediated immunity have been reported in association with the AIDS, including deficiencies in natural killer (NK) cell activity and cytomegalovirus (CMV)-specific cytotoxicity. In the present study, the in vitro effects of interleukin-2 (IL-2) and interferon beta (IFN Beta) on these abnormalities were examined to assess the potential use of these lymphokines in the immunotherapeutic treatment of this syndrome. The peripheral blood lymphocytes (PBL) from six male homosexuals with AIDS and an active CMV infection exhibited markedly depressed NK cell and CMV-specific cytotoxic lymphocyte responses compared with uninfected, heterosexual control subjects. Incubation of PBL with IFN Beta enhanced the NK cell activity and the CMV-specific cytotoxicity of only one of six and neither of two AIDS patients, respectively, while enhancing the NK cell activity of all six control subjects. In contrast, IL-2 dramatically enhanced both the NK cell and the CMV-specific cytotoxic lymphocyte activities of all of the patients. These results indicate that IL-2 can substantially potentiate the depressed cytotoxic effector functions of PBL from AIDS patients, while IFN Beta has little effect.

Deficient autologous mixed lymphocyte reaction in Kaposi's sarcoma associated with deficiency of Leu-3+ responder T cells

Autologous mixed lymphocyte reaction (AMLR) and T cell subsets defined with monoclonal antibodies were analyzed in the peripheral blood of homosexual males with Kaposi's sarcoma (KS). All seven patients demonstrated decreased AMLR (P less than 0.001) when compared with age- and sex-matched simultaneously studied controls. These patients also showed decreased proportions of Leu-3+ (helper/inducer phenotype) and an increase in the proportion of Leu-2+ (suppressor/cytotoxic phenotype) T cells. Leu-3+ T cells were purified from two patients by depleting Leu-2+ T cells in complement-dependent cytotoxicity. Leu-3+ T cells from both patients demonstrated poor proliferative response in the AMLR. In allogeneic MLR, patients' T cells were poor responders and their non-T cells were poor stimulators against healthy controls. This study demonstrates deficiency of both AMLR and allogeneic MLR in patients with KS. The decreased AMLR is associated with qualitative and functional deficiency of Leu-3+ responder T cells. Whether the functional deficiency of Leu-3+ responder T cells in the AMLR is a general phenomena or a feature of a subset of patients with KS remains to be determined.

Killing of measles virus-infected cells by human cytotoxic T cells

Lymphocytes from normal individuals were tested for the capacity to generate measles virus-specific cytotoxic T-cell responses after in vitro stimulation with measles virus. Approximately 12% (5 of 40) of the normal adults tested produced significant cytotoxic responses. The cytotoxic response was measles virus specific both at the level of stimulation and at the effector level. Studies of the specificity of cytotoxic effectors from five normal donors by direct lysis or cold target inhibition or both indicated that most, if not all, of the virus-specific activity was self-specific. A detailed analysis of one donor (W6) indicated that measles-specific cytotoxicity was largely HLA-A and -B restricted; unexplained cross-reactive lysis was observed with some targets, but this lysis appeared to be HLA related, since all of the targets expressed HLA-B12. An analysis of the cellular requirements for the production of measles-immune cytotoxic T lymphocytes demonstrated that T cells and macrophages (depleted of natural killer and K cells) were sufficient for the generation of killer cells. Most of the cytotoxic effector activity was mediated by OKT3+ OKT4- OKT8+ cells.