Introduction

Ageing and a pro-inflammatory milieu, such as present in patients with end-stage renal disease, are important drivers of increased T-cell differentiation, which is accompanied by loss of the co-stimulatory molecule CD28. CD4⁺CD28^null T cells have a highly cytotoxic, inflammatory profile and respond to IL-15 and IL-21 in particular. These cells have been associated with an increased as well as a decreased risk for rejection after renal transplantation. Therefore, we wanted to investigate the alloreactive potential of CD4⁺CD28^null T cells in detail.

Materials and methods

FACS-sorted CD4⁺CD28^null and CD4⁺CD28⁺ T cells were stimulated with HLA-mismatched CD3-depleted cells in the absence or presence of exogenous cytokines. The alloreactive potential was evaluated by measuring proliferation, degranulation (CD107a expression), content of cytotoxic molecules and cytokine production.

Results

Compared with CD4⁺CD28⁺ T cells, the CD4⁺CD28^null T cells showed an almost absent proliferation, degranulation and cytokine production in response to allogeneic stimulation. Addition of IL-15 (with/without IL-21) to the cell culture increased the frequency of proliferating CD4⁺CD28^null T cells significantly up to 30% (p<0.001) without altering CD28 expression. Next to this, the combination of IL-15 and IL-21 also increased CD107a expression within the CD4⁺CD28^null T cells (p<0.05). Furthermore, granzyme B and perforin positivity seemed to be higher when IL-15 and IL-21 were added to the allogeneic condition within CD4⁺CD28^null T cells compared to the allogeneic condition without these cytokines. Also, allogeneic-expanded CD4⁺CD28^null T cells were capable to lyse allogeneic target cells in a specific lysis assay. Finally CD4⁺CD28^null T cells after alloantigen stimulation in the presence of IL-15 +/- IL-21 produced more IFN-γ and TNF-α (p<0.05 for IFN-γ and p<0.01 for TNF-α).

Conclusion

CD4⁺CD28^null T cells need exogenous cytokines, in particular IL-15, to proliferate and secrete inflammatory cytokines in response to allogeneic stimulation.

CITATION INFORMATION: Dedeoglu B, Litjens N, Kraaijeveld R, Verschoor W, Baan C, Betjes M. CD4⁺CD28^null T Cells Require IL-15 & IL-21 to Become Alloresponsive. Am J Transplant. 2017;17 (suppl 3).

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