Low-dose interleukin-2 -loaded nanoparticle effect on NK and T-reg cell expression in experimentally induced type 1 diabetes mellitus

Introduction: Type 1 diabetes mellitus is an autoimmune disorder characterized by inflammatory damage to pancreatic beta cells resulting in loss of insulin secretion. In autoimmune type 1 diabetes mellitus (T1D) natural killer cells (NK) initiate pancreatic islets cell lyses in autoimmune T1D. Loss of T regulatory cells (Treg) at disease onset facilitates the activation and accumulation of NKs in the pancreatic microenvironment. A proper low-dose interleukin 2 (IL-2) could enhance Tregs and enforce control and regulation of pro-inflammatory NKs. Aim: This relation needs to be studied to improve therapeutic strategies aimed at resetting the balance between Tregs and proinflammatory cells. Material and methods: We used novel formulations of low-dose IL-2 loaded on chitosan nanoparticles. The study included 116 T1D BALB/c mice experimentally induced by streptozotocin, divided into groups. Their splenocytes were maintained in a short-term culture for assessment of expression of CD4+FOXP3+ Treg and NKp46+NK by both flow cytometry and enzyme-linked immunoassay (ELISA). Morphological, immunohistochemical, and morphometrical analyses were done. In vitro suppressor assay was used to assess the suppressor effect of Treg cells after exogenous IL-2 treatment. Results: NK cell expression, NKp46 level, and NK cell functions were modulated more in mice injected with IL-2-loaded chitosan nanoparticles than in other groups. A statistical inverse correlation was found between Treg and NK cell expression in IL-2-loaded chitosan with 0.3 mu IU (p = 0.047), and this correlation was related to FOXP3 expression on Treg cells. The modified expression of NK and NKp46 was noticed in mice injected with 0.3 mu IU for longer duration (3 weeks) (p < 0.001), but the NK functions did not show any significant changes with prolonged treatment. Conclusions: Prolonged administration of low-dose IL-2 results in the vigorous expression of NKp46, indicating a significant role of Tregs in NK stimulation and motivation. Low-dose IL-2 selectively modulates NKp46 NK and FOXP3+ Tregs and increases their expression.

Automated summary

The study showed that injection of novel formulations of low-dose IL-2 loaded on chitosan nanoparticles modulated NK and NKp46 expression levels in mice, with a negative correlation between Treg expression and NK expression. Prolonged administration of low-dose IL-2 resulted in vigorous expression of NKp46, indicating the significant role of Tregs in regulating NK activity.