Phenotypic and Functional Profile of Peripheral Blood Lymphomonocytes in Seborrheic Dermatitis.

Summary

The protocol describes a prospective, monocentric pilot study conducted at the Istituto Dermatologico San Gallicano (IFO-ISG) aimed at investigating the phenotypic and functional profile of peripheral-blood lymphomonocytes in individuals with seborrheic dermatitis (SD) compared with non-affected controls. A secondary objective is to explore dietary habits in subjects with SD.

Seborrheic dermatitis is a chronic-relapsing inflammatory skin disease, common in infancy, puberty, and adulthood (40-60 years). Its multifactorial etiology involves:

Sebaceous gland hyperactivity and altered lipid composition promoting Malassezia proliferation;

Metabolic activation of sebaceous glands by Malassezia, which generates irritating fatty acids;

Immune dysregulation, influencing keratinocyte activation and differentiation;

Barrier disruption, clinically resulting in erythema, scaling, and pruritus.

Previous research on immune cells in barrier tissues (gut, lung, skin) suggests that environmental factors-particularly dietary fatty acids and salt intake-modulate the functional polarization of Th17 vs. Treg cells, with implications for autoimmunity. Tissue-resident memory T cells (TRM), abundant in barrier organs, display site-specific homing markers such as CCR4, CCR10, CXCR4, GATA6, and BCL6. In contrast, circulating TEM and TEMRA subsets share common profiles across tissues.

Protocollo\_Profilo fenotipico e…

In skin, Th17 cells exhibit variable transcriptional states that may reflect tissue-dependent functional states rather than fixed subtypes. Studies in SD have mainly focused on cutaneous immune responses, highlighting roles for Tγδ cells, cytokines (IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-17, TNF-α), and β-defensins, linked to dendritic-cell maturation driven by sebaceous lipids and activation of the NLRP3 inflammasome. Malassezia can also induce IL-1β release from dendritic cells in vitro. However, little is known about how SD affects circulating immune cells or how dietary patterns influence systemic immune responses in this disease.

Study population

The study will include 15 SD patients and 15 non-affected (NA) controls, aged 45-75 years, of both sexes. SD patients must have mild-to-moderate facial involvement and must have stopped topical or systemic treatments for at least two weeks. Exclusion criteria include other skin diseases, neurodegenerative disorders, immunosuppression, ongoing treatments, or HIV positivity. Controls are selected from IFO staff, relatives, and individuals undergoing routine dermatologic examinations.

Methods

After overnight fasting, participants undergo venous blood sampling (7 mL). Plasma is separated and stored at -80°C for secretory and lipidomic profiling. Lymphomonocytes are isolated using Ficoll-Hypaque gradients and analyzed by flow cytometry to characterize immunological phenotypes. Each participant completes a dietary questionnaire at enrollment. Collected data include demographics, clinical history, dietary information, laboratory findings, and SD-specific clinical data (for the patient group).

Statistical plan

As a pilot study, data will be summarized with descriptive statistics only; no formal comparisons will be performed. Findings will generate hypotheses for future research. Recruitment is planned over 18 months, with a total study duration of 24 months.

Ethical and administrative aspects

The study adheres to Good Clinical Practice, the Declaration of Helsinki, and EU/national regulations. Ethical approval is required before initiation. Participants must provide written informed consent for both study participation and data processing. Data will be handled in compliance with GDPR, using pseudonymization, secure storage, and restricted access. Authorized monitors and regulatory authorities may inspect source documents. Biologic samples will be stored until completion of analyses. Results will be published in aggregated, non-identifiable form in scientific journals and conferences.

Conditions

• Seborrheic Dermatitis
• Dietary Habits

Sponsors & Collaborators

• San Gallicano Dermatological Institute IRCCS

  lead OTHER

Eligibility

Min Age

45 Years

Max Age

75 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2024-06-19

Primary Completion

2025-02-14

Completion

2025-06-10

Countries

• Italy

Study Locations