Examination of the Immunological Role of Toll-Like Receptor 9 on Red Blood Cells.

Red blood cells (RBCs) were historically regarded as immunologically inert; however, current research has revealed their active participation in the innate immune response through the expression of various surface immune receptors. Notably, the nucleic-acid-sensing receptor toll-like receptor 9 (TLR9) enables RBCs to sequester and scavenge cell-free DNA under basal conditions and to deliver DNA during inflammatory states. Consequently, the presence of TLR9 on RBCs endows them with distinct immune functions. Novel techniques were developed to study the immunological function of red blood cells. This paper delineates the methodologies for detecting TLR9 on mammalian RBCs (murine, human, chimpanzee, and bat) and isolating and preparing murine RBCs for transfusion, as well as for binding CpG DNA oligodeoxynucleotides to RBCs for both in vitro and in vivo studies. These methodologies are crucial for evaluating the contributions of RBCs to the immune response.