CCR8 on human thymocytes functions as a human immunodeficiency virus type 1 coreceptor.

To determine whether human immunodeficiency virus type 1 (HIV-1) coreceptors besides CXCR4 and CCR5 are involved in HIV-1 infection of the thymus, we focused on CCR8, a receptor for the chemokine I-309, because of its high expression in the thymus. Similar levels of CCR8 mRNA were detected in immature and mature primary human thymocytes. Consistent with this, [(125)I]I-309 was shown to bind specifically and with similar affinity to the surface of immature and mature human thymocytes. Fusion of human thymocytes with cells expressing HIV-1 X4 or X4R5 envelope glycoprotein was inhibited by I-309 in a dose-dependent manner. In addition, I-309 partially inhibited productive infection of human thymocytes by X4, R5, and X4R5 HIV-1 strains. Our data provide the first evidence that CCR8 functions as an HIV-1 coreceptor on primary human cells and suggest that CCR8 may contribute to HIV-1-induced thymic pathogenesis.

CCR9A and CCR9B: two receptors for the chemokine CCL25/TECK/Ck beta-15 that differ in their sensitivities to ligand.

We isolated cDNAs for a chemokine receptor-related protein having the database designation GPR-9-6. Two classes of cDNAs were identified from mRNAs that arose by alternative splicing and that encode receptors that we refer to as CCR9A and CCR9B. CCR9A is predicted to contain 12 additional amino acids at its N terminus as compared with CCR9B. Cells transfected with cDNAs for CCR9A and CCR9B responded to the chemokine CC chemokine ligand 25 (CCL25)/thymus-expressed chemokine (TECK)/chemokine beta-15 (CK beta-15) in assays for both calcium flux and chemotaxis. No other chemokines tested produced responses specific for the cDNA-transfected cells. mRNA for CCR9A/B is expressed predominantly in the thymus, coincident with the expression of CCL25, and highest expression for CCR9A/B among thymocyte subsets was found in CD4+CD8+ cells. mRNAs encoding the A and B forms of the receptor were expressed at a ratio of approximately 10:1 in immortalized T cell lines, in PBMC, and in diverse populations of thymocytes. The EC50 of CCL25 for CCR9A was lower than that for CCR9B, and CCR9A was desensitized by doses of CCL25 that failed to silence CCR9B. CCR9 is the first example of a chemokine receptor in which alternative mRNA splicing leads to proteins of differing activities, providing a mechanism for extending the range of concentrations over which a cell can respond to increments in the concentration of ligand. The study of CCR9A and CCR9B should enhance our understanding of the role of the chemokine system in T cell biology, particularly during the stages of thymocyte development.

Fusion of monocytes and macrophages with HIV-1 correlates with biochemical properties of CXCR4 and CCR5.

Human macrophages can be infected more efficiently by M-tropic than by T-tropic HIV-1 strains, despite surface expression of both CXCR4 and CCR5 co-receptors. Western blot analyses of total cell extracts and surface proteins from multiple sets of monocytes and macrophages demonstrated substantial differences between CXCR4 molecules. CXCR4 was mainly a monomer in monocytes, but was mainly a species of higher molecular weight (90 kDa) on the surface of macrophages. CCR5 was monomeric in both cell types. A constitutive association between CD4 and the co-receptors was seen in monocytes and macrophages. However, CD4 co-precipitated with CCR5 and CXCR4 monomers, but not with the high-molecular-weight forms of CXCR4, indicating that the high-molecular-weight CXCR4 species in macrophages are not available for association with CD4, which may contribute to the inefficient entry of T-tropic strains into mature macrophages.

Co-ligation of alpha4beta1 integrin and TCR rescues human thymocytes from steroid-induced apoptosis.

Maturation of thymocytes represents a sequence of events during which thymocytes expressing TCR with moderate avidity for self antigen/MHC are positively selected, whereas those with high or insufficient TCR avidity die. Glucocorticoids are produced intrathymically and can contribute to apoptosis of unselected thymocytes. Thymocytes differentiate in a close contact with epithelial cells, expressing vascular adhesion molecule-1 (VCAM-1) and secreting glucocorticoids, with bone marrow-derived macrophages, and with extracellular matrix containing fibronectin (FN) and collagen. Their contact with FN is mediated by alpha4beta1 and alpha5beta1 integrins. We examined the contribution of TCR and integrin signaling to the survival of thymocytes from dexamethasone (Dex)-induced apoptosis. We demonstrate that FN and VCAM-1 (both of which bind alpha4beta1 integrin), but not collagen, considerably augment TCR-mediated protection of thymocytes from Dex-induced apoptosis. This 'survival' signal is transduced through the alphabeta1, but not through the alpha5beta1 integrin. The observed protection from Dex-induced apoptosis correlated with an increase in bcl-2 protein levels. FN-alpha4beta1 and VCAM-1-alpha4beta1 engagement induced up-regulation bcl-2 protein, while alpha5beta1 binding to FN induced a negative signal that was blocked by anti-alpha5beta1 antibody. These data suggest that alpha4beta1 integrin may contribute to protection of thymocytes with moderate avidity TCR from glucocorticoid-induced death during intrathymic maturation.

CXCR4 and CCR5 on human thymocytes: biological function and role in HIV-1 infection.

Thymocyte infection with HIV-1 is associated with thymic involution and impaired thymopoiesis, particularly in pediatric patients. To define mechanisms of thymocyte infection, we examined human thymocytes for expression and function of CXCR4 and CCR5, the major cell entry coreceptors for T cell line-tropic (T-tropic) and macrophage-tropic (M-tropic) strains of HIV-1, respectively. CXCR4 was detected on the surface of all thymocytes. CXCR4 expression on mature, high level TCR thymocytes was similar to that on peripheral blood T cells, but was much lower than that on immature thymocytes, including CD34+ thymic progenitors. Consistent with this, stroma-derived factor-1 (SDF-1) induced calcium flux primarily in immature thymocytes, with CD34+ progenitors giving the strongest response. In addition, SDF-1 mRNA was detected in thymic-derived stromal cells, and SDF-1 induced chemotaxis of thymocytes, suggesting that CXCR4 may play a role in thymocyte migration. Infection of immature thymocytes by the T-tropic HIV-1 strain LAI was 10-fold more efficient than that in mature thymocytes, consistent with their relative CXCR4 surface expression. Anti-CXCR4 antiserum or SDF-1 blocked fusion of thymocytes with cells expressing the LAI envelope. In contrast to CXCR4, CCR5 was detected at low levels on thymocytes, and CCR5 agonists did not induce calcium flux or chemotaxis in thymocytes. However, CD4+ mature thymocytes were productively infected with the CCR5-tropic strain Ba-L, and this infection was specifically inhibited with the CCR5 agonist, macrophage inflammatory protein-1beta. Our data provide strong evidence that CXCR4 and CCR5 function as coreceptors for HIV-1 infection of human thymocytes.

[The role of immunological changes in diseases in regions contaminated by radionuclides after the accident at the Chernobyl Atomic Electric Power Station]. / O roli immunologicheskikh izmenenii pri nekotorykh zabolevaniiakh v raionakh, zagriaznennykh radionuklidami posle avarii na ChAES.

Autoimmune deviations, both humoral and cellular, related to antigens of thyroid gland, microsomes and thyroglobulin, were observed in residents of controlled districts of Bryansk and Tula regions of Russia. The importance of these deviations at hyperplasia of thyroid gland was demonstrated. In formation of cataracts under chronic influence of low doses of ionizing radiation the humoral autoimmune mechanisms are active but not the cellular ones. The increased content of antibodies against the antigens of crystalline lens found in the residents of the controlled regions shows the possibility to develop initial manifestations of cataract under the effect of low radiation doses.

Human peripheral blood CD4+ and CD8+ T cells express Th1-like cytokine mRNA and proteins following in vitro stimulation with heat-inactivated Brucella abortus.

Defining the pattern of lymphokine production associated with Brucella abortus is critical for advancing the development of B. abortus as a vaccine carrier. In the present study we investigated the ability of heat-inactivated B. abortus or lipopolysaccharide from B. abortus to induce lymphokine production from purified human T cells in vitro. Gamma interferon (IFN-gamma), interleukin-2 (IL-2), IL-4, and IL-5 induction was assayed by mRNA-specific PCR and by enzyme-linked immunosorbent assay and bioassay for protein production. Following depletion of monocytes and B cells, B. abortus increased IFN-gamma and IL-2 mRNA expression in purified T cells compared with expression in unstimulated cells. In contrast, no IL-5 mRNA expression and only transient low-level IL-4 mRNA expression and no IL-4 protein secretion were detected. Phytohemagglutinin or phorbol myristate acetate plus ionomycin induced mRNA and protein for all these cytokines. Similar results were obtained with LPS purified from B. abortus. Removal of NK cells did not reduce lymphokine production, and enriched NK cells did not express IFN-gamma mRNA or secrete IFN-gamma protein in response to B. abortus, indicating that NK cells were not the responding population. Both CD4+ and CD8+ populations produced IFN-gamma and IL-2 in response to B. abortus. Preincubation of resting T cells with B. abortus or LPS from B. abortus for 7 days induced their differentiation into Th1-like cells as judged by their subsequent lymphokine response to phorbol myristate acetate plus ionomycin. These results suggest that B. abortus can induce differentiation of Th0 into Th1-type cells.

[Mechanisms of immunodeficiency in HIV infection and ways of overcoming it]. / Mekhanizmy immunodefitsita pri infektsii VICh i puti ego preodoleniia.

Though antibodies against HIV-1 appearing in the course of infection are successfully used for the diagnostic purposes, their accumulation on the earlier step leads to: firstly, to the rapid generation of the immunodeficiency by different mechanisms and secondly, to inefficiency of immunotherapy. One of the causes for immunodeficiency seems to be antibodies which are induced in the HIV-infected person by the HIV peptides homologous to the MHC class II molecules by their amino acid sequences. 73% of HIV-1 positive sera are shown to react with human B-lymphoma cells expressing surface class II molecule. The binding is caused by the antibodies preventing the murine monoclonal anti-HLA.DR Ab interaction with B-lymphoma. Three amino acid sequences are identified in both alpha- and beta-chain of the HLA.DR antigen, these sequences being homologous to HIV-1 gp120 or gp42 molecules for 50 to 70%. Using synthetic peptides it was shown that HIV-1-infected persons contain antibodies which cross-react to the homologous peptides of the HIV-1 and of the MHC class II. It is supposed that such antibodies shield the class II molecule on the surface of their own antigen-presenting cell which may lead to immunodeficiency caused by the anti-HIV-1 antibody.

Antibodies to MHC class II peptides are present in HIV-1-positive sera.

Seventy-five per cent of sera from HIV-1-infected individuals bind to the human B-lymphoma cells bearing the major histocompatibility class II molecule in enzyme-linked immunosorbent assay (ELISA). The binding is caused by the antibodies against the class II molecule present in the serum samples which prevent the interaction of murine anti-HLA.DR monoclonal antibody with B lymphoma in FACS analysis. The three highly conserved amino acid sequences in alpha- and beta-chains of the class II molecule and three homologous fragments in HIV-1 gp120 and gp41 were identified by computer search and synthesized. Using these peptides it was demonstrated that 28-48% of HIV-positive sera contain antibodies that cross-react with the peptide of HIV-1 origin and with the peptide from the class II molecule as well.

[Synthesis and biological activity of aminophenylphosphonic derivatives of levorin]. / Poluchenie i biologicheskaia aktivnost' aminofenilfosfonistykh proizvodnykh levorina.

Reactions of levorin, a polyenic macrolide antibiotic, with aromatic aldehydes and hypophosphorous acid resulted in formation of its amino phenylphosphonium derivatives. Physicochemical and biological properties of the derivatives were studied. The levorin amino phenylphosphonium derivatives were shown to be low toxic and have antifungal and antiviral activities.

Mechanism of MHC class II restriction in the interaction between specific suppressor and responder T cells in a proliferative response: Ia interaction with a putative anti-self receptor, expressed on pre-activated responder cells.

For the inhibition of T-lymphocyte proliferation in mixed lymphocyte culture (MLC) by in vivo alloantigen-induced specific T-suppressor cells (Ts), the Ts and responder cells must have major histocompatibility complex (MHC) class II identity, either in I-C or in I-A + I-E. In the case of I-C, the molecule is on the surface of the Ts and not on the surface of the stimulator or responder cells. This lack of I-C on the responder cells occurs even after pre-activation by antigen. I-J on the Ts is unimportant in the present system. By blocking the Ts surface molecules with antibody, it was shown that the two Ts genetic restrictions were due to distinct Ts subsets, bearing I-C in one case and I-A + I-E in the other. Pretreatment of the Ts with anti-I-C antibodies (without complement) did not prevent specific Ts binding to the alloantigen, as shown by absorption on monolayers. However, it blocked the ability of the Ts to cause suppression and this could be reversed by removal of the antibody with pronase. The responder population, when pre-activated, could be fractionated by absorbing on monolayers of syngeneic Ts. Under these conditions, the cells sensitive to suppression adhered to the monolayer, while the non-adherent cell could not be suppressed. It is proposed that a receptor, to an Ia molecule (I-C or I-A + I-E) of the Ts, appears on the surface of the pre-activated responder T cell and that this is required for the genetically restricted interaction between the responder cell and the Ts.

[Molecular and genetic approaches to the study of the regulation of the function of T-suppressor cells specific for histocompatibility molecule epitopes]. / Molekuliarnye i geneticheskie podkhody k izucheniiu reguliatsii funktsii T-supressorov, spetsifichnykh k épitopam molekuly gistosovmestimosti.

Using the model of T-suppression (Ts) induction by i/v injection of irradiated allogeneic splenocytes we were able to show that such specific Ts (1) have their own precursors and express unique membrane markers; that (2) the genetic restriction of Ts/responder interaction (interactional restriction) is based on the direct contact of an Ia molecule on Ts membrane and a putative syngeneic anti-Ia receptor, which appears on the membrane of responder lymphocyte after its activation by an allo-antigen; and that (3) the Ts receptors unlike that of other T-subsets recognize simple serologically defined determinants in the context of an MHC molecule. The practical application of the information of the Ts properties is discussed.

[Interaction of Ia-molecule of specific T-suppressor with complementary structure of syngeneic responding T-lymphocyte]. / Vzaimodeistvie Ia-molekuly spetsificheskogo T-supressora s komplementarnoi strukturoi singennogo reagiruiushchego T-limfotsita.

To achieve inhibition of proliferation of alloantigen-induced T-lymphocytes in mixed lymphocyte culture by specific suppressor T cells (SSTC), identity of SSTC and responder in MHC class II antigens is required; either in IC or in IA + IE. By shielding of the SSTC with antiserum to ICd product (without complement), it is demonstrated that ICd product is expressed on the SSTC surface only, rather than on the surface of both stimulator and responder cells (native or preactivated with the alloantigen). Pretreatment of SSTC with anti-ICd antibodies in the absence of complement does not prevent specific SSTC interaction with the alloantigen, but prevents the SSTC function in reversible fashion. Because part of responders preactivated with an alloantigen acquired a capacity to adhere to the syngeneic SSTC monolayer, it is supposed that a receptor to the syngeneic Ia-molecule of SSTC membrane arises on the surface of preactivated responder T cells, which results in direct interaction between these two cells, reflecting the "interactional restriction" mechanism of SSTC function.

[The products of class II histocompatibility complex (IC or IA+IE) restrict the interaction between specific T-suppressor and responder T-cells]. / Produkty kompleksa gistosovmestimosti klassa II (IC ili IA+IE) restriktiruiut vzaimodeistvie mezhdu spetsifichnym T-supressorom i reagiruiushchei T-kletkoi.

Spleen T cells of mice which were i.v. immunized with large dose of irradiated allogeneic lymphocytes inhibit donor alloantigen-activated DNA synthesis in mixed lymphocyte culture. To assure suppressor function, specific suppressor T cells (SSTC) both need to contact an antigen and ought to interact with responder T lymphocyte as well. Such an interaction is restricted in MHC class II genes: in IA + IE complex or in IC. IJ sub-region product present on the SSTC is not involved into the suppressor-responder interaction. By shielding of the SSTC markers with poly- and monoclonal antibodies to IC, IA and IE molecules, it is shown that two variants of suppression restriction are due to the respective SSTC sub-populations: only one of them bears ICd determinant, while both possess IAk and IEk antigens. The functions of SSTC sub-populations and their connection with immune response "interactional restriction" are discussed.

[Separation of rat serum antisuppressor antibodies eliminating T-suppressors and stimulating their generation in mice in vivo]. / Razdelenie antisupressornykh antitel syvorotki krysy, éliminiruiushchikh T-supressory i stimuliruiushchikh ikh obrazovanie u myshei in vivo.

Immunization of rats with enriched murine specific T-suppressors (STS) permitted obtaining the antisuppressor serum (ASS) which selectively inactivated in vitro the capacity of the STS to inhibit the proliferation of T-lymphocytes in a mixed lymphocyte culture in response to allo-antigens. Two opposite effects of the ASS in vivo were demonstrated: elimination of T-suppressors (on ASS administration 4 days after immunization) and stimulation of their formation (on ASS administration before immunization or to non-immunized mice). It is assumed that the two opposite effects of the ASS in vivo are caused by two different types of antibodies to unidentified markers of STS to an antigen of differentiated STS and to an antigen expressed on their precursors.

[Ia antigens: markers of specific T suppressors immune to H-2 complex antigens]. / Ia-antigeny--merkery spetsificheskikh T-supressorov, immunnykh k antigenam kompleksa H-2.

Two antisera to Ia antigens, products of the H-2 complex I-Cd and I-JkEk subregions, respectively, have been obtained by immunisation of the F1 hybrids of recombinant strains of mice. These antisera are shown to display the 50 per cent cytotoxic effect in vitro in the presence of complement upon lymphocyte populations immune to the H-2 complex antigens and enriched for specific suppressor T cells (SSC) by fractionation on the monolayer of target cells. The specificity of anti-Ia cytotoxins is shown by the cross antibody absorption with T- and B-cells of mice originated from the recombinant H-2 haplotypes and bearing either particular I-Cd, I-Jk and I-Ek antigens, or their combinations. Anti-I-Cd cytotoxins are found to react with both B and T cells at a different rate, and the anti-I-JkEk serum contains two antibody types directed to I-Ek and I-Jk products, respectively, the latter being able to react preferently with T cells. Although both antisera do inactivate the in vitro SSC function in the presence of complement at a similar degree, the inactivating action of the anti-I-Cd serum, but not that of the anti-I-JkEk serum, occurs without complement. SSC are established to bear both Ia-antigens, I-J and I-C on the same cell, as demonstrated by the cross antibody absorption and variation of the H-2 origin of SSC. These two markers are suggested to function differently in the SSC immune to the H-2 antigens and the I-C antigen expression on the SSC surface is presumed to be required for their interaction with the inhibited responder T cells proliferating in MLC.

[Selective inactivation of specific T-suppressors immune to H-2 complex antigens and prevention of their generation in vivo by antisuppressor xenogenic antibodies]. / Izbiratel'naia inaktivatsiia spetsificheskikh T-suppressorov, immunnykh k antigenam kompleksa H-2, i predotvrashchenie ikh generatsii in vivo antisupressornymi ksenogennymi antitelami.

Rats were immunized with mouse lymphocytes enriched by the absorption-elution technique with specific suppressor T-cells (STC) immune to antigens of the H-2 complex. The anti-suppressor sera (ASS) obtained being absorbed with mouse erythrocytes and lymph node cells killed in the presence of complement about 30 per cent of the STC-enriched cell population and inactivated the STC in vitro function in a selective fashion, not affecting the function of other T-cell subclasses, killers and MIF-producers, immune to the same H-2 antigens. The STC inactivating ASS action occurred partly in the absence of complement irrespective of the STC strain origin, STC immunological specificity in the H-2 system and the intensity of the STC activity. This ASS action was abolished by exhaustion of antibodies only with STC containing cell suspensions. In contrast, intact (non-enriched) mouse STC appeared to be able to induce a mixture of rat antibodies inactivating partly all three T-cell subclasses assayed. Infections of ASS to mice prevented them from the in vivo STC generation and gave rise to inhibition of the syngeneic tumor growth in the specifically preimmunized mice.