Red blood cells from Python regius are insensitive to α‐hemolysin from Escherichia Coli

α‐hemolysin (HlyA) from Escherichia coli lyses red blood cells (RBCs). HlyA‐pores insert themselves into the RBC membrane, allowing influx of cations and water, which results in swelling and lysis1. HlyA‐induced hemolysis of mammalian RBCs requires ATP release, P2 receptor and pannexin channel activation2. Blocking P2 receptors, pannexin channels or scavenging extracellular ATP reduces HlyA‐induced hemolysis. Here we test if this also applies to reptilian RBCs by spectrophotometry, live cell imaging and flow cytometry. We found Python regius RBCs resistant to HlyA‐induced hemolysis compared to human RBCs. HlyA concentrations causing maximal hemolysis of human RBCs did not affect P. regius RBCs. A 30‐fold rise in HlyA concentration did, however, cause significant hemolysis. This is not explained by a general resistance to lysis as P. regius RBCs were more vulnerable to osmotically induced hemolysis compared to human RBCs. The low HlyA‐sensitivity in python RBCs did not result from lack of purinergic signaling, as P. regius RBCs shrunk when exposed to 3mM ATP indicating the presence of a P2X 7 ‐like receptor. The P2 receptor antagonist PPADS and the pannexin blocker carbenoxolone reduced hemolysis. The data imply that P. regius RBCs express P2 receptors, which as in mammals amplify HlyA‐induced hemolysis. The HlyA‐resistance of python RBCs may reflect membrane properties reducing the ease of bacterial toxin insertion. The project was funded by The Danish Council for Independent Research, Medical Sciences.