Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 0 0 2026 10 06 1 12 Hassan Khorramian Department of Veterinary Pathobiology, SR.C, Islamic Azad University, Tehran, Iran Gholamreza Nikbakht Brujeni Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Pejman Mortazavi Department of Veterinary Pathobiology, SR.C, Islamic Azad University, Tehran, Iran Seyed Mohsen Razavi Department of Oncology, Firoozgar Hospital, Iran University of Medical Sciences, Tehran, Iran 2026 04 11 2026 06 19 Monoclonal antibodies targeting CD52 (alemtuzumab) and immune checkpoint inhibitors targeting programmed death-ligand 1 (PD-L1, also known as CD274) have shown therapeutic potential in chronic lymphocytic leukemia (CLL). This study compared surface expression of CD52 and PD-L1 between treated and untreated patients with CLL. A total of 67 patients were divided into 2 groups: a treatment group (n=23) comprising patients currently receiving therapy or in remission, and a follow-up group (n=44) consisting of untreated patients under regular monitoring. After obtaining ethical approval, peripheral blood samples were collected and analyzed by flow cytometry using monoclonal antibodies against CD5, CD19, CD23, CD52, and PD-L1. No statistically significant differences were observed in CD19+, CD23+, or PD-L1 expression between the 2 groups. However, CD52+ expression was significantly higher in the treatment group (43.77% vs 25.46%). The treatment group also showed significantly higher CD5+ expression (35.05% vs 18.93%), while the CD23+CD52+ population was significantly higher in the follow-up group (43.30% vs 20.72%). Higher levels of CD5+ and CD52+ may be associated with treatment requirement in patients with CLL. These findings are hypothesis-generating and require prospective validation in cohorts with survival endpoints. We do not claim prognostic equivalence to established markers such as TP53 disruption. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/4792 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/4792/2434