Presentation of soluble antigen to human T cells by products of multiple HLA-linked loci: analysis of antigen presentation by a panel of cloned, autologous, HLA-mutant Epstein-Barr virus-transformed lymphoblastoid cell lines

Role of Keratinocytes in Antigen Presentation and Polarization of Human T Lymphocytes

Allergic contact dermatitis is a T-cell-mediated inflammatory skin disease in which interaction between skin keratinocytes and migrating T lymphocytes may play a critical part. In this study, the role of keratinocytes as allergen-/antigen-presenting cells (APCs) leading to activation of T lymphocytes is investigated using a human epidermal cell line A431. It is known that cultured cells do not express human leucocyte antigen (HLA) and hence can be used as APCs independent of HLA profile of both APCs and T cells from human volunteers. This cell line responded to common allergens and irritants by inducing or upregulating the cell-surface expression of HLA-DR, and intercellular adhesion molecule-1 and B7 mRNA transcripts in keratinocytes. In addition, allergen-primed A431 cells also induced allergen-specific proliferation of human T lymphocytes in cocultures. Anti-HLA-DR, interleukin-1alpha (IL-1alpha) antibodies and lysosomotropic agent chloroquine inhibited the proliferation. Allergens also upregulated cytokines IL-1alpha, granulocyte-macrophage colony-stimulating factor, Gro-alpha and IL-12 in keratinocytes. Further, keratinocytes activated by allergens induced polarization of activated T lymphocytes to the Th1 phenotype.

Antigenic properties and processing requirements of 65-kilodalton mannoprotein, a major antigen target of anti-Candida human T-cell response, as disclosed by specific human T-cell clones

T-cell-mediated immunity is known to play a central role in the host response to Candida albicans. T-cell clones are useful tools for the exact identification of fungal T-cell epitopes and the processing requirements of C. albicans antigens. We isolated human T-cell clones from an HLA-DRB1*1101 healthy donor by using an antigenic extract (MP-F2) of the fungus. Specific clones were T-cell receptor alpha/beta and CD4(+)/CD8(-) and showed a T-helper type 1 cytokine profile (production of gamma interferon and not interleukin-4). The large majority of these clones recognized both the natural (highly glycosylated) and the recombinant (nonglycosylated) 65-kDa mannoprotein (MP65), an MP-F2 minor constituent that was confirmed to be an immunodominant antigen of the human T-cell response. Surprisingly, most of the clones recognized two synthetic peptides of different MP65 regions. However, the peptides shared the amino acid motif IXSXIXXL, which may be envisaged as a motif sequence representing the minimal epitope recognized by these clones. Three clones recognized natural and pronase-treated MP65 but did not detect nonglycosylated, recombinant MP65 or the peptides, suggesting a possible role for polysaccharides in T-cell recognition of C. albicans. Finally, lymphoblastoid B-cell lines were efficient antigen-presenting cells (APC) for recombinant MP65 and peptides but failed to present natural, glycosylated antigens, suggesting that nonprofessional APC might be defective in processing highly glycosylated yeast proteins. In conclusion, this study provides the first characterization of C. albicans-specific human T-cell clones and provides new clues for the definition of the cellular immune response against C. albicans.

Reduction in serum IL-6 after vacination of breast cancer patients with tumour-associated antigens is related to estrogen receptor status

Elevated serum IL-6 concentrations have been associated with poor prognosis in a variety of cancers, and decreases in serum IL-6 concentrations have been reported after chemotherapy. We have demonstrated that serum IL-6 concentrations are elevated in breast cancer patients [normal women 0.7 +/- 2.5 pg/ml (n=36), breast cancer patients 38.3 +/- 138.7 pg/ml (n = 111)]. After vaccination of breast cancer patients with a combination of tumour-associated antigens and biological adjuvants (IL-2 and GM-CSF), the concentration of IL-6 decreased significantly (P<0.05) to 8.1 +/- 14.6 pg/ml (n=85). Other studies have shown that oestrogen suppresses IL-6 production in oestrogen receptor positive breast cancer cells. We have demonstrated that the decrease in IL-6 associated with vaccination is related to the oestrogen receptor status of the tumours from breast cancer patients, as a decrease in IL-6 from 124.0 +/- 267.5 pg/ml (n=26) to 6.2 +/- 11.0 pg/ml (n=34) only occurs in patients with oestrogen receptor negative tumours. The IL-6 concentration in breast cancer patients with oestrogen receptor positive tumours remained unchanged (9.5 pg/ml before vaccination, and 9.3 pg/ml after vaccination). These results suggest that postmenopausal women with oestrogen receptor negative breast cancers, who do not respond well to either hormonal therapy with tamoxifen or adjuvant chemotherapy, may have a significant response to vaccination with autologous tumour-associated antigens.

T-cell epitopes in variable segments of Chlamydia trachomatis major outer membrane protein elicit serovar-specific immune responses in infected humans

We previously identified 18 stimulatory Chlamydia trachomatis major outer membrane protein (MOMP) peptides containing at least 23 epitopes presented with various HLA class II allotypes. Only one peptide contained an epitope localized in a variable segment (VS2). Continued studies reported here identified a total of five VS peptides containing T-cell epitopes that are distributed among MOMPs VS1, VS2, and VS4. Only MOMP-primed T-cell cultures from subjects infected with serovar E responded to the serovar E VS peptides, while the response of such cultures to constant-segment peptides was independent of the infecting serovar. Furthermore, MOMP-primed T cells proliferated in response only to the VS peptides encoded in serovar E but not to the corresponding peptides derived from serovar F, I, or J, confirming that these responses were serovar specific.

Induction of HLA Class I-Restricted CD8+ CTLs Specific for the Major Outer Membrane Protein of Chlamydia trachomatis in Human Genital Tract Infections

HLA class I-restricted CD8+ CTLs specific for the major outer membrane protein (MOMP) of Chlamydia trachomatis are present in the peripheral blood of humans who acquired genital tract infections with the organism. Three HLA-A2-restricted epitopes and two HLA-B51-restricted epitopes were identified in serovar E-MOMP. One of the five epitopes spans a variable segment of MOMP and is likely a serovar E-specific epitope. The other four epitopes are localized in constant segments and are C. trachomatis species specific. CTL populations specific for one or more of the four constant segment epitopes were isolated from all 10 infected subjects tested, regardless of infecting serovars, but from only one of seven uninfected subjects tested. The CTLs failed to recognize corresponding peptides derived from Chlamydia pneumoniae MOMP, further suggesting that they indeed resulted from genital tract infections with C. trachomatis. Significantly, ME180 human cervical epithelial cells productively infected with C. trachomatis were killed by the MOMP peptide-specific CTLs. Further investigations of the ability of such CTLs to lyse normal infected epithelial cells and their presence at inflamed sites in the genital tract will help understand the protective or pathological role of CTLs in chlamydial infections. The MOMP CTL epitopes may be explored as potential components of a subunit vaccine against sexually transmitted diseases caused by C. trachomatis. Moreover, the knowledge provided here will facilitate studies of HLA class I pathways of chlamydial Ag processing and presentation in physiologically relevant human APCs.

Generation of antigen-presenting cells for soluble protein antigens ex vivo from peripheral blood CD34+ hematopoietic progenitor cells in cancer patients

Peripheral blood CD34+ hematopoietic cells (PBPC) mediate hematopoietic reconstitution in cancer patients after autologous transplantation and can be expanded ex vivo in the presence of colony-stimulating factors. This study shows that functionally active antigen-presenting cells (APC) for soluble proteins are generated and expanded in these PBPC cultures. CD34+ cells were cultured ex vivo in medium containing stem cell factor, interleukin-1 beta (IL-1 beta), IL-3, IL-6, and erythropoietin (EPO). The cells from these cultures developed into very potent APC of tetanus toxoid and purified derivative of tuberculin for autologous T cells in vitro. The antigen-presenting capacity of these cell was maintained for at least 38 days of culture. These APC resembled immature cells of the myelomonocytic cell lineage by surface marker, immunocytochemistry and ultrastructural analysis. Such APC might be able to present antigens from certain tumors to the immune system.

Epstein-Barr virus-transformed B cells, a potentially convenient source of autologous antigen-presenting cells for the propagation of certain human cytotoxic T lymphocytes

Antigen-specific cytotoxic T cells (CTL) are generally elicited in vitro by incubation of effector cells with an appropriate major histocompatibility complex-matched antigen-presenting cell (APC). In the case of CTL derived from inbred rodents, spleen cells from an animal of the same strain serve as a ready source of autologous major histocompatibility complex-identical APC. In outbred human populations, however, a convenient source of human leukocyte antigen-matched APC is ordinarily difficult to obtain, and for that reason human antigen-specific CTL may be difficult to propagate. We describe a method whereby Epstein-Barr virus-transformed human B cells (B-LCL) serve as a convenient source of efficient APC for the propagation of human antigen-specific CTL. B-LCL are produced by using B cells from the donor under study and are thus human leukocyte antigen identical to the donor. Using this method, we have propagated human CD4+ Toxoplasma gondii-specific CTL for up to 9 months in vitro, during which time the cells retained their functional capability.

Generation of specific anti-melanoma reactivity by stimulation of human tumor-infiltrating lymphocytes with MAGE-1 synthetic peptide

The MAGE-1 gene encodes a tumor-specific antigen, MZ2-E, which is recognized by cloned, specific cytolytic T cells (CTL) derived from the peripheral blood of a patient with melanoma. We have produced a MAGE-1-specific CTL line derived from the tumor-infiltrating lymphocytes (TIL) of a melanoma patient by weekly restimulation with autologous EBV-B cells pulsed with the synthetic HLA-A1-restricted MAGE-1 epitope nonapeptide EADPTGHSY. The 1277.A TIL line grew in long-term culture in low-dose interleukin-2 (IL-2) and IL-4, and exhibited antigen-specific, MHC-class-I-restricted lysis of HLA-A1-bearing MAGE-1+ cell lines. Cytolysis of target cells pulsed with the synthetic MAGE-1 decapeptide KEADPTGHSY was superior to that of cells pulsed with the immunodominant nonapeptide. Single amino-acid or even side-chain substitutions in the immunodominant nonamer abrogated cytolysis. 1277.A TIL specifically secreted tumor necrosis factor alpha after co-incubation with HLA-A1-expressing MAGE-1+ cell lines or fresh tumor. These data suggest that tumor-antigen-specific, MHC-restricted CTL may be grown from TIL in the presence of synthetic epitope peptides and expanded for adoptive immunotherapy in melanoma patients.

Melanoma-specific CD4+ T lymphocytes recognize human melanoma antigens processed and presented by Epstein-Barr virus-transformed B cells

While much emphasis has been placed on the role of MHC class I-restricted CD8+ T cells in the recognition of tumor-specific antigens (Ag), evidence has accumulated that CD4+ T cells also play a critical role in the anti-tumor immune response. However, little information exists on the nature of MHC class II-restricted human tumor Ag. In an attempt to develop in vitro systems to characterize such Ag, we examined the ability of Epstein-Barr virus (EBV)-transformed B cells to present melanoma-associated Ag to melanoma-specific CD4+ cells. CD4+ T cells cultured from lymphocytes infiltrating a s.c. melanoma metastasis secreted TNF-alpha and GM-CSF specifically in response to autologous cultured melanoma cells expressing MHC class II molecules. These CD4+ cells also recognized MHC class II-compatible EBV-B cells pulsed with extracts of autologous melanoma cells, but failed to recognize EBV-B cells pulsed with autologous non-transformed cells or a variety of allogeneic tumors or normal cells. B cells pre-fixed with paraformaldehyde were incapable of Ag presentation, suggesting that intracellular processing events were occurring. Antibody-blocking studies defined HLA-DR as the dominant if not exclusive restriction locus in this T-B interaction, and HLA-DR genotyping revealed DRBI*0404 to be the probable restriction element. In a second patient, a CD4+ T-cell clone cultured from a melanoma lesion recognized autologous tumor Ag presented by autologous EBV-B; no corss-reactivity was observed with the other tumor system investigated, nor with autologous CD4+ T cells specific for tetanus toxoid. These findings demonstrate that tumor Ag can be processed and presented by EBV-transformed B cells to MHC class II-restricted tumor-specific CD4+ T cells. They also provide a model system for direct identification of these tumor-derived antigens.

IL-4 decreases the expression of the monocyte differentiation marker CD14, paralleled by an increasing accessory potency

IL-4 has been found to affect the phenotype and a variety of functions of human monocytes and macrophages and has been discussed as a monocyte activating protein along with other cytokines, such as IL-1 and IL-6. In this study we compared the effects of the cytokines IL-1, IL-6, IL-4, and a combination of IL-1 and IL-6 on the expression of the CD14 antigen, the FcIIIg receptor molecule CD16 and the MHC-class II molecules HLA-DR and HLA-DP. These molecules represent characteristic monocyte surface markers. Furthermore, the CD14 molecule has been described as a surface antigen of high in vivo relevance representing an indirect receptor for LPS. We further analyzed the effect of IL-4 on monocytes and macrophages with respect to their accessory function to initiate T-lymphocyte proliferation. Human peripheral blood monocytes strongly express the antigen CD14 and maintain it as a stable surface molecule during their differentiation to macrophages. Flow cytometry analysis of cultured monocytes demonstrated that cells incubated in the presence of IL-4, but not IL-1 and/or IL-6 revealed a reduced expression of the CD14 antigen in a dose- and time-dependent manner. After 3 days IL-4 treated cells were virtually CD14-negative. At the same time the expression of the CD16 antigen (FcRIIIg) was also strongly reduced, whereas the treatment with IL-4 led to an increased expression of MHC class II antigens such as HLA-DR and HLA-DP. The spontaneous low expression of HLA-DQ antigen on monocytes was not affected by any of the cytokines. Functionally, IL-4 treated CD14-negative monocytes exhibited a more than 2-fold higher activity to stimulate an accessory cell-dependent T cell proliferation. This was found in a mitogenic assay and in MLC when compared to monocytes cultured in the absence of IL-4. These observations provide further evidence that IL-4 is a major modulator of monocyte surface antigen expression. Moreover, IL-4 has an enhancer-effect on monocytes as accessory cells and therefore may be of considerable importance as a regulatory factor during monocyte development to accessory cells. Inasmuch as the CD14 molecule functions as a receptor for LPS-binding protein, our results suggest that IL-4 might also play an important regulatory role in processes initiated by bacterial lipopolysaccharides during inflammation and sepsis.

Allorecognition of HLA-DR and -DQ transfectants by human CD45RA and CD45R0 CD4 T cells: repertoire analysis and activation requirements

We have investigated the requirements for allogeneic stimulation of human CD4 T cells using HLA class II products expressed on various cellular backgrounds. Human (class II-negative RJ2.2.5 mutant) B cell lines transfected with HLA-DR or -DQ cDNA clones were efficient stimulators for highly purified CD4 T cells. HLA-DR-transfected mouse L cells or IFN-gamma-induced human fibroblasts, although able to function as accessory cells for T cell responses to the mitogen PHA, failed to stimulate strong T cell alloresponses. On the basis of these observations, we have employed class II transfectants to address the following questions: (a) do CD45RA and CD45R0 subpopulations differ in their allogeneic activation requirements, (b) are these subpopulations skewed in their recognition of HLA-DQ vs. HLA-DR in a manner which might support the concept that CD45RA T cells are involved in HLA-DQ-restricted suppressor inducer functions and (c) by using transfectants expressing individual HLA-DR or -DQ heterodimers in combination with limiting dilution analysis, can one for the first time obtain estimates of precursor frequencies for allogeneic cells recognizing each of these class II isotypes? Our results show that CD45RA and CD45R0 T cells respond comparably to optimal numbers of stimulator cells. However, when CD45RA and CD45R0 T cell populations depleted of endogenous accessory cells were cultured with limiting numbers of stimulator cells, CD45R0 cells generally responded more strongly, consistent with the elevated levels of various adhesion molecules known to be expressed by this population. Further, we found a similar representation of responses to HLA-DR and -DQ antigens among populations expressing CD45RA and CD45R0 isoforms. Finally, the precursor frequencies of allogeneic CD4 T cells responding to particular HLA-DR alleles were higher than to -DQ, but only by a factor of about 1.6, indicating that HLA-DQ recognition may occur more frequently than implied from previous antibody blocking studies.

HLA antigens in ocular tissues. III. Antigen presentation by gamma interferon-treated cultured uveal cells

In previous studies we have shown that normal human uveal cells, with the exception of vascular endothelium, do not express class I or class II HLA antigens in vivo. Class I antigens are induced in vitro by a variety of cytokines, while class II antigens are only induced by gamma interferon. In this study we examine the capacity of cultured uveal cells, rendered class II HLA antigen positive by gamma interferon, to present antigen to T cells. Cultured uveal cells were found to present antigen (tetanus toxoid, PPD, and Candida albicans) to T cells, but only when they were pretreated with gamma interferon. This function of uveal cells was antigen specific and MHC restricted and was blocked by class II-specific monoclonal antibodies, indicating the crucial role of class II HLA antigens in antigen presentation.

DY determinants, possibly associated with novel class II molecules, stimulate autoreactive CD4+ T cells with suppressive activity

A set of T cell clones (TCC) isolated from HLA-DR-, Dw-, DQ-matched allogeneic MLCs was found to proliferate autonomously when stimulated with cells carrying a wide range of class I or II specificities. This apparently unrestricted proliferation was relatively weak, and only low levels of IL-2 were present in the supernatants of stimulated cells. Autologous as well as allogeneic PBMC and B lymphoblastoid cell lines (B-LCL) were capable of stimulating such clones, which were also restimulated by suppressive, but not by helper, TCC. Moreover, such clones displayed the unusual property of autostimulation. mAb inhibition experiments suggested that class II- or class II-restricted antigens were involved in stimulation. Thus, certain "broad" mAbs (TU39, SG520) reacting with multiple locus products inhibited activation of these reagents, but none of those reacting more specifically with DR (TU34, TU37, L243, Q2/70, SG157), DQ (TU22, SPV-L3, Leu 10), or DP (B7/21), or mixtures of these mAbs, were able to do so. Evidence from sequential immunoprecipitation experiments suggested that mAb TU39 bound class II-like molecules other than DR, DQ, and DP on TCC and B-LCL, and it is therefore proposed that such putative novel class II-like molecules may carry the stimulating determinants for these autoreactive clones. DY-reactive clones lacked helper activity for B cells but mediated potent suppressive activity on T cell proliferative responses that was not restricted by the HLA type of the responding cells. Suppressive activity was induced in normal PBMC by such clones, as well as by independent suppressive clones, which was also inhibited only by mAb TU39. These findings lead to the proposal that DY-reactive autostimulatory cells may constitute a self-maintaining suppressive circuit, the level of activity of which would be regulated primarily by the availability of IL-2 in the microenvironment.

Differential antigen presentation by heat-treated peripheral blood mononuclear cells and Epstein-Barr virus-transformed lymphoblastoid cell lines (EBV-LCL): heated EBV-LCL present alloantigen and soluble antigen but are deficient in the stimulation of autologous EBV-LCL primed T cells

Heat-treated PBM (1 hr at 45 degrees C) cannot present soluble Candida albicans antigens (CAN) or stimulate in the mixed lymphocyte culture (MLC) reaction. This is despite their continued expression of serologically defined class II MHC antigens. In contrast, heat-treated EBV-LCL present soluble CAN and stimulate allogeneic T cells in the MLC. Heated EBV-LCL stimulate strong secondary responses from allogeneic alloprimed T-cell lines in the primed lymphocyte test (PLT), while heated PBM stimulate only weak secondary allogeneic responses. To test whether this difference was due to a subtle difference in the thermal stability of the functional expression of class II MHC antigens on PBM and EBV-LCL cells, the EBV-LCL cells were heated for 1 hr at temperatures from 45 degrees C to 60 degrees C. Even after treatment at 60 degrees C, the heated EBV-LCL strongly stimulated alloreactive T cells in MLC and PLT reactions. Heated EBV-LCL are not nonspecifically mitogenic, as they do not stimulate autologous T-cell lines primed to alloantigens. However, the weak response of alloprimed T-cell lines to heated allogeneic PBM can be augmented by coculturing with autologous heated EBV-LCL, suggesting heated EBV-LCL maintain a metabolic activity necessary for allogeneic stimulation that is deficient in heated PBM. While heated EBV-LCL stimulate allogeneic alloprimed T-cell lines, they no longer stimulate autologous EBV-LCL primed T-cell lines; irradiated EBV-LCL stimulate both strongly. This suggests the involvement of a heat labile antigenic or metabolic factor in the T-cell recognition of autologous but not allogenic EBV-LCL.