RESUMEN
Vγ9Vδ2 T cells contribute to the immune response against many tumor types through their direct cytotoxic activity and capacity to regulate the biological functions of other immune cells, such as dendritic cells and IFN-γ-producing CD8+ T cells. However, their presence in the tumor microenvironment has also been associated with poor prognosis in breast, colon and pancreatic cancers. Additionally, recent studies demonstrated that cytokines can confer some plasticity to Vγ9Vδ2 T cells and promote their differentiation into cells with regulatory functions. Here, we demonstrated that activation of Vγ9Vδ2 T cells isolated from healthy donors and cultured in the presence of IL-21 favors the emergence of a subpopulation of Vγ9Vδ2 T cells that express the ectonucleotidase CD73 and inhibits T cell proliferation in a CD73/adenosine-dependent manner. This subpopulation produces IL-10 and IL-8 and displays lower effector functions and cytotoxic activity than CD73-negative Vγ9Vδ2 T cells. We also showed, in a syngeneic mouse tumor model, the existence of a tumor-infiltrating γδ T cell subpopulation that produces IL-10 and strongly expresses CD73. Moreover, maturation, IL-12 production and induction of antigen-specific T cell proliferation are impaired in DC co-cultured with IL-21-amplified Vγ9Vδ2 T cells. Altogether, these data indicate that IL-21 promotes Vγ9Vδ2 T cell regulatory functions by favoring the development of an immunosuppressive CD73+ subpopulation. Thus, when present in the tumor microenvironment, IL-21 might negatively impact γδ T cell anti-tumor functions.
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The tumor immune microenvironment contributes to tumor initiation, progression, and response to therapy. Among the immune cell subsets that play a role in the tumor microenvironment, innate-like T cells that express T cell receptors composed of γ and δ chains (γδ T cells) are of particular interest. γδ T cells can contribute to the immune response against many tumor types (lymphoma, myeloma, melanoma, breast, colon, lung, ovary, and prostate cancer) directly through their cytotoxic activity and indirectly by stimulating or regulating the biological functions of other cell types required for the initiation and establishment of the anti-tumor immune response, such as dendritic cells and cytotoxic CD8+ T cells. However, the notion that tumor-infiltrating γδ T cells are a good prognostic marker in cancer was recently challenged by studies showing that the presence of these cells in the tumor microenvironment was associated with poor prognosis in both breast and colon cancer. These findings suggest that γδ T cells may also display pro-tumor activities. Indeed, breast tumor-infiltrating γδ T cells could exert an immunosuppressive activity by negatively regulating dendritic cell maturation. Furthermore, recent studies demonstrated that signals from the microenvironment, particularly cytokines, can confer some plasticity to γδ T cells and promote their differentiation into γδ T cells with regulatory functions. This review focuses on the current knowledge on the functional plasticity of γδ T cells and its effect on their anti-tumor activities. It also discusses the putative mechanisms underlying γδ T cell expansion, differentiation, and recruitment in the tumor microenvironment.
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Vγ9Vδ2 T cells play an important role in the immune response to infectious agents but the mechanisms contributing to this immune process remain to be better characterized. Following their activation, Vγ9Vδ2 T cells develop cytotoxic activity against infected cells, secrete large amounts of cytokines and influence the function of other effectors of immunity, notably cells playing a key role in the initiation of the adaptive immune response such as dendritic cells. Brucella infection dramatically impairs dendritic cell maturation and their capacity to present antigens to T cells. Herein, we investigated whether V T cells have the ability to restore the full functional capacities of Brucella-infected dendritic cells. Using an in vitro multicellular infection model, we showed that: 1/Brucella-infected dendritic cells activate Vγ9Vδ2 T cells through contact-dependent mechanisms, 2/activated Vγ9Vδ2 T cells induce full differentiation into IL-12 producing cells of Brucella-infected dendritic cells with functional antigen presentation activity. Furthermore, phosphoantigen-activated Vγ9Vδ2 T cells also play a role in triggering the maturation process of dendritic cells already infected for 24 h. This suggests that activated Vγ9Vδ2 T cells could be used to modulate the outcome of infectious diseases by promoting an adjuvant effect in dendritic cell-based cellular therapies.
Asunto(s)
Brucella/fisiología , Células Dendríticas/citología , Células Dendríticas/microbiología , Receptor Cross-Talk/inmunología , Receptores de Antígenos de Linfocitos T gamma-delta/metabolismo , Linfocitos T Colaboradores-Inductores/citología , Proliferación Celular , Células Dendríticas/inmunología , Humanos , Interferón gamma/biosíntesis , Interleucina-12/biosíntesis , Linfocitos T Colaboradores-Inductores/inmunología , Linfocitos T Colaboradores-Inductores/metabolismo , Factores de Tiempo , Factor de Necrosis Tumoral alfa/biosíntesisRESUMEN
Human Vγ9Vδ2 T cells play a crucial role in early immune response to intracellular pathogens. Their number is drastically increased in the peripheral blood of patients during the acute phase of brucellosis. In vitro, Vγ9Vδ2 T cells exhibit strong cytolytic activity against Brucella-infected cells and impair intracellular growth of Brucella suis in autologous macrophages. Vγ9Vδ2 T cells use cell contact-dependent mechanisms such as the release of lytic granules and Fas-mediated signals to lyse infected macrophages and decrease the development of intracellular Brucella. Although the involvement of the T-cell receptor (TCR) in the triggering of these responses is known, other surface receptors can modulate Vγ9Vδ2 T-cell response. In this study, we have investigated a potential role of NKG2D and its ligands in the anti-infectious activity of human Vγ9Vδ2 T cells against B. suis. We show that the recruitment of NKG2D by its ligands is sufficient to induce cytokine production and the release of lytic granules through PI3K-dependent pathways, but can also increase the TCR-triggered responses of Vγ9Vδ2 T cells. We also demonstrate that the interaction between NKG2D and its main ligand expressed on Brucella-infected macrophages, UL16-binding protein 1 (ULBP1), is involved in the inhibition of bacterium development. Altogether, these results suggest a direct contribution of NKG2D and its ligands to the anti-infectious activity of Vγ9Vδ2 T cells.
Asunto(s)
Brucella/inmunología , Brucelosis/inmunología , Macrófagos/metabolismo , Subfamilia K de Receptores Similares a Lectina de Células NK/metabolismo , Linfocitos T/metabolismo , Brucella/crecimiento & desarrollo , Brucella/patogenicidad , Células Cultivadas , Citocinas , Citotoxicidad Inmunológica , Proteínas Ligadas a GPI/inmunología , Proteínas Ligadas a GPI/metabolismo , Humanos , Inmunidad Innata , Péptidos y Proteínas de Señalización Intracelular/inmunología , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Activación de Linfocitos , Macrófagos/inmunología , Macrófagos/microbiología , Macrófagos/patología , Subfamilia K de Receptores Similares a Lectina de Células NK/inmunología , Fosfatidilinositol 3-Quinasas/metabolismo , Unión Proteica , Receptor Cross-Talk , Receptores de Antígenos de Linfocitos T gamma-delta/biosíntesis , Transducción de Señal , Linfocitos T/inmunología , Linfocitos T/microbiología , Linfocitos T/patologíaRESUMEN
BACKGROUND: The recent isolation of Brucella microti from the common vole, the red fox, and the soil raises the possibility of an eventual reemergence of brucellosis in Europe. In this work, the pathogenic potential of this new Brucella species in both in vitro and in vivo models of infection was analyzed. METHODS: The ability of B. microti (as compared to that of the closely related species Brucella suis) to replicate in human macrophages and in human and murine macrophage-like cells was determined. The behavior of B. microti and B. suis was evaluated in vivo in murine models of infection with Balb/c, CD1, and C57BL/6 mice. RESULTS: B. microti showed an enhanced capacity for intramacrophagic replication compared with that of B. suis. Surprisingly, and in contrast to other species of Brucella, 10(5) colony-forming units of B. microti killed 82% of Balb/c mice within 7 days. Infection of spleen and liver with B. microti peaked at day 3, compared with B. suis infection, which peaked at day 7. Sublethal doses of B. microti induced good protection against a subsequent challenge with lethal doses. CONCLUSIONS: In experimental cellular and murine infections, B. microti exhibited a high pathogenic potential, compared with other Brucella species.
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Brucella/clasificación , Brucella/fisiología , Brucelosis/microbiología , Macrófagos/microbiología , Animales , Brucelosis/inmunología , Brucelosis/mortalidad , Humanos , Hígado/patología , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Tamaño de los Órganos , Bazo/patologíaRESUMEN
Human immunodeficiency virus type 1 (HIV-1) transcription relies on its transactivating Tat protein. Although devoid of a signal sequence, Tat is released by infected cells and secreted Tat can affect uninfected cells, thereby contributing to HIV-1 pathogenesis. The mechanism and the efficiency of Tat export remained to be documented. Here, we show that, in HIV-1-infected primary CD4(+) T-cells that are the main targets of the virus, Tat accumulates at the plasma membrane because of its specific binding to phosphatidylinositol-4,5-bisphosphate (PI(4,5)P(2)). This interaction is driven by a specific motif of the Tat basic domain that recognizes a single PI(4,5)P(2) molecule and is stabilized by membrane insertion of Tat tryptophan side chain. This original recognition mechanism enables binding to membrane-embedded PI(4,5)P(2) only, but with an unusually high affinity that allows Tat to perturb the PI(4,5)P(2)-mediated recruitment of cellular proteins. Tat-PI(4,5)P(2) interaction is strictly required for Tat secretion, a process that is very efficient, as approximately 2/3 of Tat are exported by HIV-1-infected cells during their lifespan. The function of extracellular Tat in HIV-1 infection might thus be more significant than earlier thought.
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Linfocitos T CD4-Positivos/metabolismo , Linfocitos T CD4-Positivos/virología , VIH-1/patogenicidad , Fosfatidilinositol 4,5-Difosfato/metabolismo , Productos del Gen tat del Virus de la Inmunodeficiencia Humana/metabolismo , Sitios de Unión , Membrana Celular/metabolismo , Ensayo de Inmunoadsorción Enzimática , VIH-1/crecimiento & desarrollo , Humanos , Células Jurkat , Unión Proteica , Productos del Gen tat del Virus de la Inmunodeficiencia Humana/análisisRESUMEN
BACKGROUND: HIV-1 can infect and replicate in both CD4 T cells and macrophages. In these cell types, HIV-1 entry is mediated by the binding of envelope glycoproteins (gp120 and gp41, Env) to the receptor CD4 and a coreceptor, principally CCR5 or CXCR4, depending on the viral strain (R5 or X4, respectively). Uninfected CD4 T cells undergo X4 Env-mediated autophagy, leading to their apoptosis, a mechanism now recognized as central to immunodeficiency. METHODOLOGY/PRINCIPAL FINDINGS: We demonstrate here that autophagy and cell death are also induced in the uninfected CD4 T cells by HIV-1 R5 Env, while autophagy is inhibited in productively X4 or R5-infected CD4 T cells. In contrast, uninfected macrophages, a preserved cell population during HIV-1 infection, do not undergo X4 or R5 Env-mediated autophagy. Autophagosomes, however, are present in macrophages exposed to infectious HIV-1 particles, independently of coreceptor use. Interestingly, we observed two populations of autophagic cells: one highly autophagic and the other weakly autophagic. Surprisingly, viruses could be detected in the weakly autophagic cells but not in the highly autophagic cells. In addition, we show that the triggering of autophagy in macrophages is necessary for viral replication but addition of Bafilomycin A1, which blocks the final stages of autophagy, strongly increases productive infection. CONCLUSIONS/SIGNIFICANCE: Taken together, our data suggest that autophagy plays a complex, but essential, role in HIV pathology by regulating both viral replication and the fate of the target cells.
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Autofagia , Linfocitos T CD4-Positivos/metabolismo , VIH-1/metabolismo , Apoptosis , Linaje de la Célula , Técnicas de Cocultivo , Citometría de Flujo/métodos , Proteínas Fluorescentes Verdes/metabolismo , Proteína gp120 de Envoltorio del VIH/metabolismo , Humanos , Macrólidos/farmacología , Macrófagos/metabolismo , Microscopía Electrónica de Transmisión/métodos , Fagosomas/metabolismo , Especificidad de la EspecieRESUMEN
Human invariant NKT (iNKT) cells are a unique subset of T cells, which recognize glycolipids presented by the CD1d. Among the iNKT cells, several functionally distinct subsets have been characterized according to CD4 and/or CD8 co-receptor expression. The current study is focussed on the CD4(+) iNKT cell subset and its role in an anti-infectious response. We have examined the role of CD4(+) iNKT cells on the intracellular Brucella suis growth. Our results indicate that CD4(+) iNKT cells impair the intramacrophagic growth of Brucella. This inhibition is due to a combination of soluble and contact-dependent mechanisms: IFN-gamma is weakly involved while cytotoxic activities such as the induction of the Fas pathway and the release of lytic granules are major mechanisms. The impairment of Brucella growth by CD4(+) iNKT cells requires an interaction with CD1d on macrophage surface. Also, we have shown that although CD4 regulates several biological responses of CD4(+) iNKT cells, it is not involved in their antibacterial activity. Here, we have shown for the first time that the CD4(+) iNKT cell population has antibacterial activity and thus, participates directly in the elimination of bacteria and/or in the control of bacterial growth by killing infected cells.
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Antígenos CD1d/inmunología , Brucella suis/inmunología , Brucelosis/inmunología , Antígenos CD4/inmunología , Macrófagos/inmunología , Células T Asesinas Naturales/inmunología , Degranulación de la Célula/inmunología , Citotoxicidad Inmunológica/inmunología , Proteína Ligando Fas/inmunología , Proteína Ligando Fas/metabolismo , Humanos , Interferón gamma/inmunología , Interferón gamma/metabolismo , Interleucina-4/inmunología , Interleucina-4/metabolismo , Macrófagos/metabolismo , Macrófagos/microbiología , Células T Asesinas Naturales/metabolismo , Células T Asesinas Naturales/microbiología , Factor de Necrosis Tumoral alfa/inmunología , Factor de Necrosis Tumoral alfa/metabolismo , Receptor fas/inmunología , Receptor fas/metabolismoRESUMEN
NKT cells belong to a conserved T lymphocyte subgroup that has been implicated in the regulation of various immune responses, including responses to viruses, bacteria, and parasites. They express a semi-invariant TCR that recognizes glycolipids presented by the nonpolymorphic MHC class I-like molecule CD1d, and upon activation, they produce various pro- and anti-inflammatory cytokines. Recent studies have shed light on the nature of glycolipids and the environmental signals that may influence the production of cytokines by NKT cells and thus, modulate the immune response. To better understand the regulation mechanisms of NKT cells, we explored their behavior following activation by IL-2 and investigated the signaling pathways and biological responses triggered. We demonstrated that IL-2 activates not only STAT3 and -5 and the PI-3K and ERK-2 pathways as in all IL-2 responder cells but also STAT4 as in NK cells and the p38 MAPK pathway as in alphabeta T cells. We also showed that STAT6 is activated by IL-2 in NKT cells. Moreover, IL-2 induces the production of IFN-gamma and IL-4. The ability of IL-2 to induce pro- and anti-inflammatory cytokine production, in addition to proliferation, could open new therapeutic approaches for use in combination with molecules that activate NKT cells through TCR activation.
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Citocinas/biosíntesis , Inflamación/inmunología , Interleucina-2/farmacología , Células Asesinas Naturales/inmunología , Transducción de Señal/efectos de los fármacos , ADN/metabolismo , Activación Enzimática/efectos de los fármacos , Humanos , Interferón gamma/biosíntesis , Subunidad alfa del Receptor de Interleucina-2/inmunología , Interleucina-4/biosíntesis , Células Asesinas Naturales/enzimología , Activación de Linfocitos/efectos de los fármacos , Subgrupos Linfocitarios/efectos de los fármacos , Subgrupos Linfocitarios/enzimología , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Fenotipo , Fosforilación/efectos de los fármacos , Unión Proteica/efectos de los fármacos , Receptores de Antígenos de Linfocitos T/inmunología , Factor de Transcripción STAT4/metabolismo , Factor de Transcripción STAT6/genética , Transcripción Genética/efectos de los fármacosRESUMEN
Human Vgamma9Vdelta2 T cells play a crucial role in early immune response to intracellular pathogens. Moreover, in brucellosis, these cells are drastically increased in the peripheral blood of patients during the acute phase of infection. In vitro, Vgamma9Vdelta2 T cells are capable of inhibiting Brucella growth and development through a combination of mechanisms: 1) cytotoxicity, 2) macrophage activation and bactericidal activity through cytokine and chemokine secretion, and 3) antibacterial effects. We previously described that antibacterial factors were found in supernatants from activated Vgamma9Vdelta2 T cells. In this study, we show that Vgamma9Vdelta2 T cells express the human cathelicidin hCAP18 and its mature form, known as LL-37, is released upon activation of Vgamma9Vdelta2 T cells. We also show that LL-37 has an antibacterial effect on Brucella suis. Overall, our results demonstrate that LL-37 is a soluble factor responsible for a part of the bactericidal activity of Vgamma9Vdelta2 T cells.
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Péptidos Catiónicos Antimicrobianos/inmunología , Brucella suis/inmunología , Receptores de Antígenos de Linfocitos T gamma-delta/fisiología , Linfocitos T/inmunología , Actividad Bactericida de la Sangre , Brucelosis/inmunología , Células Cultivadas , Humanos , Inmunidad Innata , Activación de Linfocitos , Linfocitos T/microbiología , CatelicidinasRESUMEN
Polymorphonuclear neutrophils (PMNs) are rapidly recruited to tissues upon injury or infection. There, they can encounter local and/or recruited immature dendritic cells (iDCs), a colocalization that could promote at least transient interactions and mutually influence the two leukocyte populations. Using human live blood PMNs and monocyte-derived iDCs, we examined if these leukocytes actually interacted and whether this influenced DC function. Indeed, coculture with live but not apoptotic PMNs led to up-regulation of membrane CD40, CD86, and human leukocyte antigen (HLA)-DR on DCs. Whereas CD40 up-regulation was dependent on soluble factors released by PMNs, as determined in cultures conducted in different chambers, cell contact was necessary for CD86 and HLA-DR up-regulation, a process that was inhibited by anti-CD18 antibodies, indicating that CD18 ligation was required. We also found that via a cell contact-dependent mechanism, DCs acquired Candida albicans-derived antigens from live as well as from apoptotic PMNs and could thus elicit antigen-specific T lymphocyte responses. Altogether, our data demonstrate the occurrence of cross-talk between human PMNs and DCs and provide new insights into the immune processes occurring upstream of the interactions between DCs and T lymphocytes.
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Presentación de Antígeno/inmunología , Comunicación Celular/inmunología , Células Dendríticas/inmunología , Activación de Linfocitos/inmunología , Neutrófilos/inmunología , Transducción de Señal/inmunología , Antígenos de Superficie/inmunología , Antígeno B7-2/inmunología , Antígenos CD18/inmunología , Antígenos CD40/inmunología , Candida albicans/inmunología , Candidiasis/inmunología , Células Cultivadas , Técnicas de Cocultivo , Antígenos HLA-DR/inmunología , Humanos , Inmunidad Celular/inmunología , Inmunofenotipificación , Ligadura , Fagocitosis/inmunología , Linfocitos T/inmunología , Regulación hacia Arriba/inmunologíaRESUMEN
Monocyte-derived dendritic cells (DCs) were used as an in vitro model of myeloid DCs in order to determine a minimum marker pattern with which to characterize and distinguish different stages of DC activation and maturation. Phenotypic changes induced on immature DCs by two prototypic stimuli, poly I:C and CD40 ligation, were first examined. Both elicited HLA-DR, CD40, CD86 and CXCR4 upregulation, and CCR5 downregulation, but only CD40 ligand-stimulated DCs became CD83(+)\CCR7(+), whereas poly I:C-stimulated DCs expressed lower CD83 levels and were mostly CCR7(--). CD40 ligation and poly I:C elicited increased production of inflammatory cytokines interleukin (IL)-6 and tumor necrosis factor-alpha, of IL-10 and the CCL5 chemokine, but profiles differed as to higher IL-10, IL-12 and CCL22 (a CCR4 ligand important for T cell recruitment) levels for the former, and of CCL4 and CCL5 for the latter. Thus, a limited set of phenotypic markers, cytokine and chemokine production assays, may be used to distinguish the three stages in the life of DCs: immaturity, activation and full maturation. The ability of purified protein derivative-loaded DCs to stimulate autologous T cells to produce IL-2, IL-4 and interferon-gamma indeed depended on their activation stage and endocytic activity, which decreased upon maturation. We then examined whether ligation of CD4, CCR5 and\or CXCR4, the receptor and coreceptors of human immunodeficiency virus envelope gp120, respectively, affected DC activation or maturation, neither a monoclonal antibody to the gp120-binding site on CD4 nor CCL5 nor CXCL12, the natural ligands of CCR5 and CXCR4, respectively, nor gp120 altered the DC activation and maturation processes.
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Antígenos CD40/inmunología , Diferenciación Celular/inmunología , Células Dendríticas/inmunología , Proteína gp120 de Envoltorio del VIH/inmunología , VIH/inmunología , Monocitos/inmunología , ARN Bicatenario/farmacología , Células Cultivadas , Quimiocinas CC/inmunología , Citocinas/biosíntesis , Endocitosis/inmunología , Humanos , Monocitos/citología , ARN Bicatenario/inmunología , Receptores de Quimiocina/inmunologíaRESUMEN
Dendritic cells (DCs) are likely to play a key role in immunity against Mycobacterium tuberculosis, but the fate of the bacterium in these cells is still unknown. Here we report that, unlike macrophages (Mphis), human monocyte-derived DCs are not permissive for the growth of virulent M. tuberculosis H37Rv. Mycobacterial vacuoles are neither acidic nor fused with host cell lysosomes in DCs, in a mode similar to that seen in mycobacterial infection of Mphis. However, uptake of the fluid phase marker dextran, and of transferrin, as well as accumulation of the recycling endosome-specific small GTPase Rab11 onto the mycobacterial phagosome, are almost abolished in infected DCs, but not in Mphis. Moreover, communication between mycobacterial phagosomes and the host-cell biosynthetic pathway is impaired, given that <10% of M. tuberculosis vacuoles in DCs stained for the endoplasmic reticulum-specific proteins Grp78/BiP and calnexin. This correlates with the absence of the fusion factor N-ethylmaleimide-sensitive factor onto the vacuolar membrane in this cell type. Trafficking between the vacuoles and the host cell recycling and biosynthetic pathways is strikingly reduced in DCs, which is likely to impair access of intracellular mycobacteria to essential nutrients and may thus explain the absence of mycobacterial growth in this cell type. This unique location of M. tuberculosis in DCs is compatible with their T lymphocyte-stimulating functions, because M. tuberculosis-infected DCs have the ability to specifically induce cytokine production by autologous T lymphocytes from presensitized individuals. DCs have evolved unique subcellular trafficking mechanisms to achieve their Ag-presenting functions when infected by intracellular mycobacteria.
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Células Dendríticas/inmunología , Células Dendríticas/microbiología , Líquido Intracelular/inmunología , Líquido Intracelular/microbiología , Mycobacterium tuberculosis/crecimiento & desarrollo , Mycobacterium tuberculosis/inmunología , Presentación de Antígeno , Diferenciación Celular/inmunología , División Celular/inmunología , Células Cultivadas , Células Dendríticas/citología , Células Dendríticas/metabolismo , Chaperón BiP del Retículo Endoplásmico , Humanos , Inmunidad Innata , Líquido Intracelular/metabolismo , Macrófagos/inmunología , Macrófagos/microbiología , Fagosomas/inmunología , Fagosomas/microbiología , Biosíntesis de Proteínas , Especificidad de la Especie , Tuberculina/inmunología , Tuberculina/metabolismo , Vacuolas/inmunología , Vacuolas/microbiologíaRESUMEN
Activating cells of the immune system may stimulate human immunodeficiency virus type 1 (HIV-1) replication and contribute to select pathogenic variants in vivo. Here, we examined the possible effect of a major pathway of immune activation, CD40 interaction with its ligand (CD40L), on the susceptibility of monocyte-derived macrophages (MDMs) to various HIV-1 strains. Stimulation of MDMs with CD40L led to reduced replication of R5 HIV-1(Ba-L), whereas this strongly enhanced the replication of X4 HIV-1(Lai) as well as of X4 primary isolates, and this was associated with strong cytopathic effects. The replication of X4 strains was inhibited by stromal cell-derived factor 1, an indication of the restricted usage of CXCR4 as virus coreceptor in this case. CD40L induced the activation of mitogen-activated protein kinases ERK1/ERK2 and stimulated MDMs to secrete RANTES (regulated on activation, normal T cell expressed and secreted), macrophage inflammatory protein 1alpha (MIP-1alpha), MIP-1beta, interleukin 6 (IL-6), IL-1beta, and tumor necrosis factor alpha. From this data, it may be hypothesized that activated macrophages represent a favorable environment for the replication of classically T lymphocyte-tropic X4 variants and, thus, may contribute significantly to the selection of such variants at late stages of clinical HIV-1 infection.