Fanny Delfanti

NF-κB Modulates Sensitivity to Apoptosis, Proinflammatory and Migratory Potential in Short- versus Long-Term Cultured Human γδ Lymphocytes

Vγ9Vδ2 T lymphocytes are involved in the immune response against hematological malignancies and certain pathogens through the recognition of nonpeptidic Ags expressed by tumors and infected cells. Being equipped with proinflammatory chemokine receptors, they participate to the early phases of inflammation acting as both effector and connector cells between innate and adaptive immunity. We show in this study that after initial TCR triggering short- and long-term cultured γδ lymphocytes differ in their susceptibility to activation-induced apoptosis and proinflammatory phenotype. Activation-induced apoptosis was triggered by anti-CD95 mAbs or by the γδTCR stimuli isopentenyl pyrophosphate and pamidronate, the latter in the presence of monocytes. In particular, short-term cultured cells are resistant to apoptosis and characterized by expression of anti-apoptotic cellular FLIP molecules and partial spontaneous caspase-8 activation. Linked to this behavior, short-term γδ cells display constitutive activation of the transcription factor NF-κB, which is functionally related to their apoptosis-resistant phenotype. Finally, they spontaneously secreted elevated amounts of the NF-κB-regulated chemokines CCL3, CCL4, and CCL5, which likely contributed to down-modulation of the inflammatory CCR5 receptor. Conversely, long-term cultured apoptosis-sensitive γδ cells displayed uncleaved caspase-8 and no constitutive NF-κB activation; moreover, they secreted CC chemokines only upon TCR triggering coupled to the re-expression of CCR5. The expression of members of the TNF receptor family, including CD30 and TNFRII, also varied according to the time in culture. Altogether our data support a link between resistance to apoptosis and a proinflammatory phenotype in γδ T lymphocytes, unraveling the crucial role of NF-κB in regulating the switch from resistance to apoptosis susceptibility.

Dual role of TNF‐α in NK / LAK cell‐mediated lysis of chronically HIV‐infected U1 cells. Concomitant enhancement of HIV expression and sensitization of cell‐mediated lysis

The U937‐derived chronically HIV‐infected U1 cell line and uninfected U937 cell clones were efficiently lysed by both unstimulated (NK) and IL‐2‐stimulated (lymphokine‐activated killer; LAK) peripheral blood mononuclear cells (PBMC) of healthy HIV‐seronegative donors. Pretreatment of target cells with IFN‐γ down‐modulated killing of both U1 cells and two U937 cell clones, and up‐regulated MHC class I expression. In contrast, TNF‐α enhanced the sensitivity of infected U1 cells, but not of U937 cell clones to NK / LAK cell lysis. Co‐cultivation of IL‐2‐stimulated PBMC with U1 cells triggered expression and replication of HIV by cell‐cell contact, and this effect was inhibited by anti‐TNF‐α antibodies (Ab); virus production was partially inhibited by zidovudine. Of interest, anti‐TNF‐α Ab protected U1 cells from LAK cell activity. Thus, TNF‐α can induce HIV expression from chronically infected U1 cells, but also plays an important role in sensitizing these cells to lysis.

CD30 ligation differentially affects CXCR4-dependent HIV-1 replication and soluble CD30 secretion in non-Hodgkin cell lines and in γ δ T lymphocytes

We studied whether signaling through CD30, a member of the TNF receptor family, affected acute infection with HIV‐1, encompassing its entire replicative cycle. Several non‐Hodgkin cell lines, targets of CXCR4‐dependent (X4) HIV‐1 infection, were positive for CD30 expression. CD30 ligation induced up‐regulation of viral replication only in certain CD30+ cell lines. Enhancement ofX4 virus replication by CD30 engagement inversely correlated with both CD30 surface density and constitutive NF‐κB activation. Conversely, expression of CD30, but not of other members of the TNF receptor family, was proportional to constitutive NF‐κB binding. Concomitantly, secretion of soluble (s) CD30 increased in all cell lines by CD30 ligation. sCD30 release was enhanced by engagement of CD30 alone and, to a greater extent, by co‐engagement of CD3 also in primary γ δ T lymphocytes, along with complementary modulations of their surface CD30 expression. sCD30‐containing supernatant specifically inhibited HIV‐1 expression induced by CD30 engagement in chronically infected ACH‐2 T cells; thus sCD30 may act as a negative feed‐back molecule. In conclusion, we have delineated novel features of CD30 biology and underline the peculiar link of CD30 expression to constitutive NF‐κB activation which is pivotal to both HIV replication and cell survival.