Assessment of the levels of interleukin-17 and interleukin-38 in thyroid-associated ophthalmopathy patients.

PURPOSE: The objective of the study was to analyse the levels of IL-17 and IL-38 in the samples of unstimulated tears, orbital adipose tissues, and sera of patients diagnosed with active forms of TAO. The correlation of the levels of IL-17 and IL-38 with clinical activity score (CAS) was scrutinized.

METHODS

A study was conducted at the Kazakhstan Scientific Research Institute of Eye Diseases (Almaty city, Kazakhstan). Study participants (n = 70) were sub-divided into 3 groups: (1) a group of patients diagnosed with active TAO (n = 25), (2) a group of patients with an inactive form of TAO (n = 28), and (3) a "control group" (patients diagnosed with orbital fat prolapse, n = 17). All patients underwent a clinical assessment and diagnostics. The activity of the disease and its severity were assessed using the CAS and NOSPECS scales. Thyroid function tests were performed, including the study of the levels of thyroid-stimulating hormone, triiodothyronine, free thyroxine, and antibodies to the thyroid-stimulating hormone receptor. IL-17 and IL-38 levels in non-stimulated tear samples, orbital tissue, and patients' sera were measured using commercial ELISA kits.

RESULTS

The results showed that the number of former smokers prevailed among patients with active TAO (48%) in comparison with patients with inactive TAO (15.4%), p = 0.001. The concentration of IL-17 significantly increased in the samples of non-stimulated tears, adipose tissues of the orbit and sera of patients with active forms of TAO. The level of IL-38 was reduced in all types of samples (p ≤ 0.05). The results of a histological study of orbital adipose tissues in the group of patients with an active form of TAO showed the presence of focal infiltration with lymphocytes, histiocytes, plasma cells, severe sclerosis and vascular plethora. We observed an association between the CAS of patients with active TAO and the level of IL-17 in sera (r = 0.885; p = 0.001). On the contrary, a negative correlation was detected for the level of IL-38 in sera.

CONCLUSIONS

The results highlighted the systemic effect of IL-17 and the local effect of IL-38 in TAO. We observed a significant increase in the production of IL-17, and a decrease in IL-38 in samples of sera and unstimulated tears (the active form of TAO). Our data indicate a correlation of IL-17 and IL-38 levels with the clinical activity of TAO.