Disrupted Homeostatic Cytokines Expression in Secondary Lymph Organs during HIV Infection

Splenomegaly induced by anemia impairs T cell movement in the spleen partially via EPO

The spleen is an important secondary lymph organ. Splenomegaly induced by anemia could affect the function of spleen in immune responses. We observe that anemia induced in mice with reduced peripheral T cell trafficking to the spleen T cell zones as well as CCL21 and CCL19 expression. In accordance with previous research, we found that the production of EPO in the mice kidney was sharply increased post anemia. In addition, mice were injected with different doses of EPO. Our results show that with the increased dosage of EPO, the chemokine expression in the spleen is lowered with a decrease in peripheral T cell homing to the spleen T cell zones. At last, our results show that the anemia mice model administrated with anti-EPO antibody had a higher expression of spleen CCL19 and CCL21 and an increased count of periphery T cells trafficking to spleen T cell zones at day 3 post induction. These data indicate that anemia could disturb T cell movement in the spleen, which might further affect T cell immune response, with partial involvement of EPO.

Cytotoxic chemotherapy reduces T cell trafficking to the spleen by downregulating the expression of C-C motif chemokine ligand 21 and C-C motif chemokine ligand 19

T cells serve an important role in the destruction of tumor cells and clearing of foreign pathogens. Previous studies have suggested that the T cell immune response of tumor-bearing patients is significantly lower than that of healthy people, and the principal reason for this is lymphocytopenia, which is caused by repeated cycles of chemotherapy. In addition to lymphocytopenia, the present study revealed that cytotoxic chemotherapy also weakens the homing ability of T cells to the T-cell zone of the spleen, which decreases the possibility of encounters between antigen-specific T cells and dendritic cells presenting the appropriate antigen, thereby weakening the immune response of T cells. These changes are attributed to the lower expression of C-C motif chemokine ligand 21 (CCL21) and C-C motif chemokine ligand 19 (CCL19) in the spleen of secondary lymphoid organs (SLOs). Finally, the present study identified that chemotherapy affects the function and survival of fibroblastic reticular cells in SLOs, which are the main source of CCL21 and CCL19. These observations aid us in further understanding the mechanism that is responsible for the decreased T cell immune response following repeated cycles of chemotherapy.

Disrupted fibroblastic reticular cells and interleukin-7 expression in tumor draining lymph nodes

The immune system of patients with cancer is usually in an inhibitory state. Lymph node (LN) draining of pathological sites provides a suitable microenvironment where adaptive immune responses mainly occur. However, the microenvironment in the tumor draining lymph nodes (TDLNs) of patients with cancer appears to be in favor of tolerance. The effects of tumor cells on TDLNs have not been elaborated clearly. The present results have indicated that tumor cells may directly affect TDLNs by decreasing the fibroblastic reticular cell population that led to less interleukin-7 secretion. As a result, the number of T cells in TDLNs declined with reduced survival signals. A decreased number of T cells in TDLNs means weakened ability of immune surveillance. Clinically, these results were also confirmed in LN biopsies from patients with colon cancer at different clinical stages. Results of the present study showed that tumor cells may directly inhibit the immunological function of TDLNs.

Cytokines Elevated in HIV Elite Controllers Reduce HIV Replication In Vitro and Modulate HIV Restriction Factor Expression

A subset of HIV-infected individuals termed elite controllers (ECs) maintain CD4⁺ T cell counts and control viral replication in the absence of antiretroviral therapy (ART). Systemic cytokine responses may differentiate ECs from subjects with uncontrolled viral replication or from those who require ART to suppress viral replication. We measured 87 cytokines in four groups of women: 73 ECs, 42 with pharmacologically suppressed viremia (ART), 42 with uncontrolled viral replication (noncontrollers [NCs]), and 48 HIV-uninfected (NEG) subjects. Four cytokines were elevated in ECs but not NCs or ART subjects: CCL14, CCL21, CCL27, and XCL1. In addition, median stromal cell-derived factor-1 (SDF-1) levels were 43% higher in ECs than in NCs. The combination of the five cytokines suppressed R5 and X4 virus replication in resting CD4⁺ T cells, and individually SDF-1β, CCL14, and CCL27 suppressed R5 virus replication, while SDF-1β, CCL21, and CCL14 suppressed X4 virus replication. Functional studies revealed that the combination of the five cytokines upregulated CD69 and CCR5 and downregulated CXCR4 and CCR7 on CD4⁺ T cells. The CD69 and CXCR4 effects were driven by SDF-1, while CCL21 downregulated CCR7. The combination of the EC-associated cytokines induced expression of the anti-HIV host restriction factors IFITM1 and IFITM2 and suppressed expression of RNase L and SAMHD1. These results identify a set of cytokines that are elevated in ECs and define their effects on cellular activation, HIV coreceptor expression, and innate restriction factor expression. This cytokine pattern may be a signature characteristic of HIV-1 elite control, potentially important for HIV therapeutic and curative strategies.IMPORTANCE Approximately 1% of people infected with HIV control virus replication without taking antiviral medications. These subjects, termed elite controllers (ECs), are known to have stronger immune responses targeting HIV than the typical HIV-infected subject, but the exact mechanisms of how their immune responses control infection are not known. In this study, we identified five soluble immune signaling molecules (cytokines) in the blood that were higher in ECs than in subjects with typical chronic HIV infection. We demonstrated that these cytokines can activate CD4⁺ T cells, the target cells for HIV infection. Furthermore, these five EC-associated cytokines could change expression levels of intrinsic resistance factors, or molecules inside the target cell that fight HIV infection. This study is significant in that it identified cytokines elevated in subjects with a good immune response against HIV and defined potential mechanisms as to how these cytokines could induce resistance to the virus in target cells.

Lymphotoxin in physiology of lymphoid tissues - Implication for antiviral defense

Lymphotoxin (LT) is a member of the tumor necrosis factor (TNF) superfamily of cytokines which serves multiple functions, including the control of lymphoid organ development and maintenance, as well as regulation of inflammation and autoimmunity. Although the role of LT in organogenesis and maintenance of lymphoid organs is well established, the contribution of LT pathway to homeostasis of lymphoid organs during the immune response to pathogens is less understood. In this review, we highlight recent advances on the role of LT pathway in antiviral immune responses. We discuss the role of LT signaling in lymphoid organ integrity, type I IFN production and regulation of protection and immunopathology during viral infections. We further discuss the potential of therapeutic targeting LT pathway for controlling immunopathology and antiviral protection.