Lyme borreliosis diagnosis currently relies on clinical assessment and detection of Borrelia-specific antibodies. However, serology does not allow reliable assessment of active infection. Evaluation of the cellular immune response through Borrelia-specific T lymphocyte monitoring may provide complementary diagnostic and prognostic information.

This study aims to assess Borrelia afzelii-specific T-cell responses using multiparameter flow cytometry after stimulation with standardized peptide pools. This approach enables the characterization of CD4+ and CD8+ T cells, including polyfunctional immune responses.

The diagnostic and prognostic value of this immunomonitoring strategy will be evaluated in patients with acrodermatitis chronica atrophicans, a late manifestation of Lyme borreliosis associated with B. afzelii.

Inclusion Criteria:

• Age ≥ 18 years
• Subject informed of the results of the prior medical examination
• Subject informed about the objectives, procedures, and potential risks of the study
• Subject affiliated with a health insurance/social security scheme (beneficiary or dependent)
• Subject having provided dated and signed informed consent
• Lyme borreliosis/acrordermatitis chronica atrophicans (ACA) group:

Subject presenting clinical and biological criteria or Borrelia identification confirming chronic atrophic acrodermatitis, with appropriate antibiotic treatment initiated less than 18 months ago or untreated

• Control group: Healthy subject with no history of Lyme disease and negative Lyme serology

Exclusion Criteria:

• Body weight < 50 kg
• Pregnancy or breastfeeding
• Diabetes mellitus
• Immunodeficiency or ongoing immunosuppressive treatment (including oral corticosteroids)
• Contraindication to local anesthesia with lidocaine, with or without adrenaline
• Inability to provide informed consent (emergency situation, inability to understand study information, …)
• Participation in another clinical trial
• Legal protection measures (guardianship, curatorship, or legal safeguard)

A total of 20 adult participants will be enrolled, including 10 patients with late Lyme borreliosis presenting with acrodermatitis chronica atrophicans (ACA) associated with Borrelia afzelii and 10 healthy adult controls without a history of Lyme disease and with negative Lyme serology.