CD71
Overview
CD71 (Transferrin Receptor 1, TfR1) is a type II transmembrane glycoprotein that mediates cellular iron uptake by binding transferrin. CD71 is upregulated on rapidly proliferating cells, including activated lymphocytes and plasmablasts, due to the high iron demand of cell division and antibody synthesis. In flow cytometry, CD71 serves as a marker of recent activation and active proliferation.
Key Points from Literature
-
CD71 expressed on dengue acute-phase plasmablasts: Plasmablasts in acute dengue carry the phenotype CD20⁻CD38⁺⁺CD27⁺Ki67⁺CD71⁺CXCR3⁺. CD71 expression confirms active proliferation and metabolic demand, consistent with recently generated short-lived ASCs (see Ansari2025 - Peripheral T Helper Subset Drives B Cell Response in Dengue, multi-color flow cytometry, n=170 dengue cohort).
-
★ [2026-08-28] CD71 carries the same activation-vs-lineage caution as CD21^lo/CXCR5⁻/CD11c⁺ — and “Activated B cells (CD71⁺)” is one of the four incompatible expansions of “ABC”. The consensus Perspective extends to CD71 its warning that these markers “could indicate recent B cell activation rather than a permanent state of expression/lack of expression”, and lists Activated B cells — human blood, CD71⁺, which may or may not be CD11c⁺T-bet⁺ — alongside age-associated, autoimmunity-associated and atypical B cells as four mutually incompatible readings of the same acronym, which it recommends retiring. For this wiki’s use of CD71 that caution is confirmatory rather than damaging: the bullet above uses CD71 as a proliferation/metabolic readout on an already-gated plasmablast, which is exactly what the Perspective says the marker reports. The caution binds on anyone reading CD71⁺ as an identity call for the atypical/DN compartment — see Atypical B Cell and CD11c (see Eisenbarth2025 - A Roadmap for Defining Extrafollicular B Cell Responses, consensus Perspective — no original data).
-
CD71 is positioned as an early-activation marker of memory cells and of new germinal centre products — not of an extrafollicular one. The review calls CD71 “a valuable marker of early memory B cell activation”, and states that “upregulation of CD71 appears to be a helpful marker of early activation in proliferative antigen-specific memory cells and new germinal center products that differentiate into antibody-secreting PB” (see Sanz2019 - Consistent Classification of Human B Cell Populations, review — no original data). Two things follow. It corroborates the bullet above — CD71 on a dengue plasmablast is reporting proliferation and recent activation. And it cuts directly against reading CD71⁺ as an extrafollicular signature: the review’s own worked example of a CD71⁺ cell is a GC emigrant, which is the same counter-example Eisenbarth2025 - A Roadmap for Defining Extrafollicular B Cell Responses later generalises.
Contradictions & Debates
None documented in current wiki sources.
Related Pages
Plasmablast, CD38, CD20, CXCR3, CD11c, Atypical B Cell, CD27