# Estimation of the tissue and serum levels of IL-35 in Mycosis fungoides: a case-control study

## TL;DR

This study found higher levels of IL-35 in both tissue and blood of patients with Mycosis fungoides compared to healthy people, suggesting IL-35 may play a role in the disease and could help in diagnosis.

## Contribution

The study is the first to compare tissue and serum IL-35 levels in Mycosis fungoides patients and controls, identifying IL-35 as a potential diagnostic and recurrence marker.

## Key findings

- Both tissue and serum IL-35 levels were significantly higher in Mycosis fungoides patients than in healthy controls.
- Tissue IL-35 levels were significantly higher than serum levels in Mycosis fungoides patients.
- Tissue IL-35 was higher in female patients and those with recurrent disease.

## Abstract

Mycosis fungoides (MF) is the most common primary cutaneous T-cell lymphoma (CTCL) with its etiology not yet fully understood. Interleukin (IL)-35 is an inhibitory cytokine that belongs to the IL-12 family. Elevated IL-35 in the plasma and the tumor microenvironment increases tumorigenesis and indicates poor prognosis in different types of malignancies. The objective of this study is to estimate the expression levels of IL-35 in tissue and serum of MF patients versus healthy controls. This case-control study included 35 patients with patch, plaque, and tumor MF as well as 30 healthy controls. Patients were fully assessed, and serum samples and lesional skin biopsies were taken prior to starting treatment. The IL-35 levels were measured in both serum and tissue biopsies by ELISA technique. Both tissue and serum IL-35 levels were significantly higher in MF patients than in controls (P < 0.001) and tissue IL-35 was significantly higher than serum IL-35 in MF patients (P < 0.001). Tissue IL-35 was significantly higher in female patients and patients with recurrent MF compared to male patients and those without recurrent disease (P < 0.001). Since both tissue and serum IL-35 levels are increased in MF, IL-35 is suggested to have a possible role in MF pathogenesis. IL-35 can be a useful diagnostic marker for MF. Tissue IL-35 can also be an indicator of disease recurrence.

The online version contains supplementary material available at 10.1007/s00403-024-03115-9.