Assessment of PD-1 and PD-L1 tissue expression levels in lichen planus patients: a case-control study.

"Declarations Conflict of interestNone declared. Ethical approvalAll procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Ethical committee approval by the Research Ethics Committee, Faculty of Medicine, Cairo University. Study registered in Protocol Registration and Results System (ClinicalTrials.gov) registration ID: NCT04892381. Conflict of interest None declared."

"Funding Open access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB)."

"The protocol of this case–control study was revised and approved by the Research Ethics Committee of the Faculty of Medicine. ClinicalTrials.govID: NCT04892381."