Red blood cells (RBCs) are traditionally considered non-professional phagocytes functioning predominately in oxygen transport. In the present study, we examined the ability of Japanese flounder (Paralichthys olivaceus), a teleost species with important economic values, RBCs to uptake inorganic particles and bacteria in different size/form, as well as the involving endocytic pathways. We found that flounder RBCs exhibited relatively high uptake/attachment capacities for 0.1 μm-1.0 μm (diameter) latex beads, but not for 2.0 μm beads. For the 0.1 μm beads, the uptake/attachment was executed through macropinocytosis and caveolae-mediated pathway, while for 0.5 μm and 1.0 μm beads, the uptake/attachment depended primarily on macropinocytosis and partially on the caveolin-mediated pathway. In addition to latex beads, flounder RBCs also exhibited an apparent capacity to engulf both live and inactivated bacteria. For live bacteria, the endocytosis was clathrin-mediated, while for inactivated bacteria, clathrin- as well as non-clathrin-mediated endocytosis were involved. Taken together, these results demonstrated that teleost RBCs possess particle uptake/attachment and bacteria phagocytosis capacities via different pathways that depend on the physical size and biological nature of the engulfed objects.

中文翻译：

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日本比目鱼（Paralichthys olivaceus）红细胞摄取颗粒和细菌：大小依赖性和途径特异性。

传统上认为红细胞（RBC）是非专业吞噬细胞，主要在氧气运输中起作用。在本研究中，我们研究了日本比目鱼（Paralichthys olivaceus），具有重要经济价值的硬骨鱼种，RBCs吸收不同大小/形式的无机颗粒和细菌以及涉及的内吞途径的能力。我们发现，比目鱼RBC对0.1μm-1.0μm（直径）的乳胶珠表现出较高的吸收/附着能力，而对于2.0μm的珠则没有。对于0.1μm的珠子，摄取/附着是通过巨胞饮和小窝介导的途径进行的，而对于0.5μm和1.0μm的珠子，摄取/附着主要取决于巨胞饮和小窝蛋白介导的途径。除了乳胶珠 比目鱼RBC还表现出明显的吞噬活细菌和灭活细菌的能力。对于活细菌，内吞作用是网格蛋白介导的，而对于灭活细菌，网格蛋白和非clathrin介导的胞吞作用都涉及。综上所述，这些结果表明硬骨质红细胞通过不同的途径具有颗粒摄取/附着和细菌吞噬能力，​​这取决于被吞噬物体的物理尺寸和生物学性质。