Emerging concepts in the molecular cell biology and functions of mammalian erythrocytes.

Erythrocytes, or red blood cells (RBCs), are essential components of vertebrate blood, comprising approximately 45% of human blood volume. Their distinctive features, including small size, biconcave shape, extended lifespan (∼115 days), and lack of a nucleus or other membrane-bound organelles, make them unique among mammalian cell types. Traditionally regarded as passive carriers of oxygen and carbon dioxide, erythrocytes were long thought to function merely as hemoglobin (Hb)-filled sacs, incapable of gene expression or roles beyond gas transport.