Inhibitory immune receptors, including CD85d and CD305 (LAIR-1), act as immune checkpoint-like molecules. They contain immunoreceptor tyrosine-based inhibitory motifs (ITIMs) that recruit SH2-domain phosphatases (e.g., SHP-1), which suppress cellular activation (7,8).
CD85d is predominantly expressed in myeloid cells, including monocytes, macrophages, dendritic cells, and granulocytes. It is also differentially expressed on NK, T, B cells, and neutrophils. It is expressed at high levels in tumor cells, facilitating immune escape by promoting immune suppression, allowing for tumor evasion (9).
CD85d is widely expressed across AML, so it is a top candidate, due to its traditional association with myeloid phenotypes and limited expression in normal haematopoiesis (10). It was reported to be expressed in B cells of CLL patients in contrast to normal B cells. Its expression in CLL patients denotes a distinctive feature, which may be acquired during malignant transformation (8). Therefore, CD85d may have significant prognostic, mechanistic, and therapeutic roles in hematologic malignancies (11).
As a novel biomarker in solid malignant tumors to predict the prognosis of patients, upregulation of CD85d in tumors is associated with worse tumor phenotypes. Targeting CD85d may be an effective tool for targeted cancer therapy (12).
Concerning CD305, it has been reported in about 60% of CLL patients and may be used as an effective prognostic marker to predict TTFT in CLL patients (13).
Despite their potential clinical significance, the expression patterns of CD85d and CD305 across B-cell lymphoid neoplasms subtypes remain incompletely identified. Illustrating their role may help to determine TTFT, prognosis, therapeutic targeting, and refinement of B-cell neoplasms classification in line with WHO-HAEM5 standards.