Culture‐differentiated CD8 + T cells acquire innate memory‐like traits and respond to a pathogen‐associated molecule

[Oxidized low-density lipoprotein modulates differentiation of murine memory CD8+ T cell subpopulations]

OBJECTIVE

To investigate effect of oxidized low-density lipoprotein (ox-LDL) on memory CD8⁺ T cell subpopulation differentiation in mice with autoimmune diabetes.

METHODS

Cultured splenic CD8⁺ T cells from pre-diabetic NOD mice isolated with magnetic beads were treated with 30 µg/mL ox-LDL and 10 U/mL interleukin-2 (IL-2) for 24 h and the control cells were treated with IL-2 only. Flow cytometry was used to determine the percentage of splenic CD8⁺IFN-γ⁺ T cells, expressions of CD8, CD44 and CD62L on the T cells, and the activation of T cell factor-1 (TCF-1) and STAT-3. The CD127⁺ memory T cells were purified and transplanted into the pre-diabetic NOD mice via the tail vein, and the blood glucose was recorded weekly and survival time of the mice was monitored.

RESULTS

Treatment with ox-LDL significantly reduced islet β cell-specific cytotoxic CD8⁺T cells as compared with the control group [(0.7∓0.03)% vs (2.7∓0.14)%, P<0.01]. The percentage of effector memory CD8⁺T cells (Tem) in the total memory CD8⁺T cells was reduced [(10.3∓0.71)% vs (30.3∓1.36)%, P<0.01] and that of stem cell-like memory T cells was significantly increased [(72.3∓3.8)% vs (55.1∓2.61)%, P<0.05] following ox-LDL treatment, which also resulted in significantly decreased activation of TCF-1 [(14.5∓0.82)% vs (34.2∓1.23)%, P<0.01] and pSTAT-3 [(3.3∓0.12)% vs (22.1∓1.1)%, P<0.01]. Transplantation of ox-LDL-treated memory T cells in pre-diabetic NOD mice obviously inhibited the increase of blood glucose and prolonged the survival time of the mice (P<0.05).

CONCLUSION

Ox-LDL decreases the activation of transcriptional factors TCF-1 and phosphorylation of STAT-3, inhibits the formation of effector memory CD8⁺ T cells with long-term cytotoxicity, but promote the generation of stem cell-like memory CD8⁺ T cells, which result in suppression of islet β cell-specific effector cytotoxic CD8⁺ T cell differentiation to lessen autoimmune injury to the islet β cells.

LPS stimulates and Hsp70 down-regulates TLR4 to orchestrate differential cytokine response of culture-differentiated innate memory CD8(+) T cells

Nonconventional innate memory CD8(+) T cells characteristically expressing CD44, CD122, eomesodermin (Eomes) and promyelocytic leukemia zinc finger (PLZF) were derived in culture from CD4(+)CD8(+) double positive (DP) thymocytes of normal BALB/c and C57BL/6 mice. These culture-differentiated cells constitutively express toll-like receptor (TLR)4 and release interferon (IFN)-γ and interleukin (IL)-10. We show the TLR4-ligand lipopolysaccharide (LPS) stimulate the TLR and up-regulate IFN-γ skewing the cells towards type 1 polarization. In presence of LPS these cells also express suppressor of cytokine signaling (SOCS)1 and thus suppress IL-10 expression. In contrast, heat shock protein (Hsp)70 down-regulated TLR4 augmenting the anti-inflammatory cytokine IL-10. In association with IL-10 release IFN-γ was abrogated. The programmed cell death (PD)-1 mostly present in regulatory T cells was stimulated in these IL-10 producing cells by Hsp70 and not LPS indicating the cells can be driven to two contrast outcomes by the two TLR4 ligands. Our work provides a scope for in vitro monitoring of CD8(+) T cells to decipher important immune therapeutic option during infection or sepsis.