Detection of erythrophagocytosis in loggerhead’s blood

The phagocytosis of red blood cells (RBCs) is due to changes on the erythrocyte surface: specific modifications of RBC membrane components, alteration of surface molecules, loss of RBC membrane phospholipid asymmetry and irreversible oxidative damage of SH groups (Bratosin et al., 1998). In man erythrophagocytosis by neutrophils and monocytes is detectable in the autoimmune hemolytic anemia associated with paroxysmal cold hemoglobinuria and has been observed in some patients manifesting clonal hematopoietic malignancies with myelodysplasia (Mukhopadhyay et al, 2003; Lewandowski et al., 2011). Phagocytosis by macrophages is a highly conserved phenomenon among vertebrates and it has been postulated that the pathophysiology of erythrophagocytosis may likewise be similar in reptiles and mammals (Nevill, 2009). In Caretta caretta the heterophils, analogous to the mammalian neutrophils, can phagocyte both parasitized and normal-appearing erythrocytes. On circulating blood smears stained with MGG-stained smears of circulating Caretta blood demonstrated that 4-51% of the heterophils were emitting pseudopodia that made contact with erythrocytes and that others had progressively encircled individual erythrocytes. These are mature erythrocytes containing a typical inclusion body, recognized as Heinz body (Basile et al., 2011). Moreover, teardrop-shaped RBCs were also identified in the blood films suggesting that the phagocytosing cell aspirates or selectively removes the inclusion body from the erythrocyte and permits the resultant dacrocyte to remain in the circulation. A comparable phenomenon, the pitting function of the spleen, is well know in man. In this case the phagocytic cells of the spleen remove remnants of DNA (Jolly bodies) from denucleated erythrocytes and allow them to persist in circulation. This pitting results in a efficient removal of the inclusion bodies contained in RBC cytoplasm by releasing dacryocytes into circulation. The positivity to ALP MPO and CAE reactions also confirmed that the loggerhead’s phagocyting cells are heterophils. In conclusion loggerhead’s erythrophagocytosis is a defense mechanism allowing both the complete degradation of infected/parasitized erythrocytes and the pitting of the inclusion body and the release of an healthy erythrocyte into circulation. References: Basile Filomena, Di Santi Annalisa, Caldora Mercedes, Ferretti Luigi, Bentivegna Flegra, Pica Alessandra. Inclusion bodies in loggerhead erythrocytes are associated with unstable hemoglobin and resemble human Heinz bodies. J. Exp. Zool. 313A DOI: 10.1002/jez.687. Bratosin D, Mazurier J, Tissier JP, Estaquier J, Huart JJ, Ameisen JC, Aminoff D, Montreuil J. (1998) Cellular and molecular mechanisms senescen erythrocyte phagocytosis by macrophages. A review. Biochimie 80, 173-195. Lewandowski K, Homenda W, Mital A, Complak A, Hellmann A. (2011) Erythrophagocytosis by neutrophils - a rare morphological phenomenon resulting in acquired haemolytic anaemia? Int J Lab Hematol. doi: 10.1111/j.1751-553X.2011.01312.x. Mukhopadhyay Sanjay, Keating Lawrence and Souid Abdul-Kader. (2003) Erythrophagocytosis in Paroxysmal Cold Hemoglobinuria. American Journal of Hematology 74:196–197.