# Age- and Genotype-Associated Specific Expression of IL-1 and TNF Receptors on Immunocompetent Cells

## TL;DR

This study shows how aging and genetic differences affect the expression of inflammation-related receptors on immune cells, with monocytes being especially impacted.

## Contribution

The study reveals age- and genotype-specific changes in IL-1 and TNF receptor expression on immune cells, emphasizing monocytes and the role of genetic polymorphisms.

## Key findings

- Monocytes from younger individuals show higher expression of TNFR1, TNFR2, and IL-1R1 compared to older individuals.
- Genetic polymorphisms influence receptor expression in an age- and cell-type-specific manner.
- Receptor downregulation in older adults may be a response to chronic inflammation, suggesting a dynamic link between genetics and immune aging.

## Abstract

Aging is accompanied by a chronic, low-grade inflammatory state known as “inflammaging,” largely driven by dysregulated signaling of pro-inflammatory cytokines like IL-1 and TNF-α. The biological impact of these cytokines is modulated by the expression of their cellular receptors, which is influenced by genetic polymorphisms. However, the interplay between age, genetic variation, and cell-type-specific receptor expression remains incompletely characterized. This study aimed to determine the relative and absolute expression levels of IL-1 and TNF receptors on major immunocompetent cell populations in healthy donors of different age groups and to assess the influence of receptor gene polymorphisms on this expression. A cohort of 144 healthy donors was stratified into two age clusters using unsupervised clustering: a “young” group (18–31 years, n = 71) and an “older” group (32–59 years, n = 73). Membrane expression of TNFR1, TNFR2, IL-1R1, and IL-1R2 on T-lymphocytes, B-lymphocytes, and monocytes was analyzed by flow cytometry. The analysis included both the percentage of receptor-positive cells and the number of receptors per cell using absolute quantification with calibration beads. Genotyping for eight SNPs in the TNF1, TNFR2, IL1R1, and IL1R2 genes was performed via PCR-RFLP. The most pronounced age-related differences were observed in monocytes, in which the young cohort exhibited a significantly higher percentage of TNFR1- and TNFR2-positive monocytes, as well as a higher number of IL-1R1 receptors. In contrast, T-lymphocytes from the older cluster showed a higher percentage of TNFR2-positive cells. Genetic polymorphisms significantly modulated receptor expression in an age-dependent manner. For example, in the young cluster, polymorphisms primarily affected receptor levels on B-lymphocytes, whereas in the older cluster, the most significant associations were observed in monocytes. This study reveals significant, cell-specific alterations in the IL-1 and TNF receptor landscapes with age, with monocytes being particularly affected. The observed receptor downregulation in older adults is likely to reflect an active process of ligand-induced desensitization driven by chronic inflammation. Furthermore, genetic polymorphisms exert age-dependent effects on receptor expression, highlighting the dynamic interplay between genetics and immunosenescence. These findings provide a foundation for personalized strategies to mitigate inflammaging.