Page 15 - Science Focus (Issue 016)

Case Study 個案分析

The Red Bone Marrow School – Macrophage and 紅骨髓學校 — 巨噬細胞和幼紅血球
Erythroblast
The functions of macrophage are not merely about 巨噬細胞的功能不止是與體內的免疫防禦有關，它在紅血
the immune defense in our body; macrophage also 球生成（erythropoiesis；即紅血球的成長）中也起著關鍵作用。
plays a critical role in erythropoiesis, in other words, RBC 在第六集中，這過程被描述為「紅血球的教育」。以下將會討論
development. In episode 6, the process is depicted as
the “schooling of RBC”. Let’s focus on the following two 其中兩個重要概念：
important concepts mentioned!
The First Concept: Macrophage as a Teacher of RBC 概念一：紅血球的老師 — 巨噬細胞

• What is the "school of RBCs" in reality? • 現實中「紅血球的學校」是什麼？
The “school” in the animation represents the red bone 動畫中的「學校」代表紅骨髓，那裡是紅血球生成的地方。在紅
marrow, where RBCs are produced. In the red bone 骨髓中，有一些稱為「幼紅細胞島」（erythroblastic islands）
marrow, there are structures called “erythroblastic islands”
where many erythroblasts surround a central macrophage. 的結構，許多幼紅血球會在這裡圍繞著位於中央的巨噬細胞。
The central macrophage is similar to the teacher at school 中央巨噬細胞的角色類似於學校裡的老師，會培育圍繞着它的
and it nurtures the nearby erythroblasts. [7]
幼紅血球 [7]。
• What exactly does macrophage "teach" erythroblasts?
It is suggested that macrophages actively assist in the • 巨噬細胞實際上怎樣「教育」幼紅血球？
development of erythroblasts by providing iron (recycled 有研究提出巨噬細胞會透過向幼紅血球提供鐵（從老化或受損
from the aged or damaged RBCs) for heme synthesis [7, 8]. 的紅血球中回收得來的），供其合成血紅素之用，從而積極協助
They also provide proliferative and survival signals to the 幼紅血球的發育 [7, 8]。它們還為幼紅血球提供增生和生存信
erythroblasts, and are involved in erythroblast enucleation
[7]. 號，並參與幼紅血球的脫核過程 [7]。

The Second Concept: Erythroblast Enucleation 概念二：幼紅血球的脫核
• How does macrophage help with the erythroblast • 巨噬細胞如何幫助幼紅血球脫核？
enucleation (removal of nucleus)? 在紅血球成熟的最後階段，幼紅血球必須排出其細胞核，而巨噬
In the final stage of RBC maturation, erythroblast has to
expel its nucleus, and macrophage helps phagocytose 細胞則會吞噬排出的細胞核 [7]。在動畫中，這被描繪成一個畢
the expelled nucleus [7]. In the animation, this is depicted 業典禮，當中學生所戴著的貝雷帽上的毛球被老師（巨噬細胞）
as the graduation ceremony in which the fur balls 移除。
on the students’ berets are removed by the teacher
(macrophage). • 去除細胞核的重要性是什麼？
• What is the importance of the removal of nucleus? 脫核後，紅血球將擁有額外的空間容納更多血紅蛋白，因此可以
After enucleation, RBC will have extra capacity for more 攜帶更多的氧。它還允許紅血球變成其獨特的雙凹圓盤狀，通過
hemoglobin, and hence, more oxygen. It also allows RBC
to turn into its distinctive biconcave shape which facilitates 增加表面積與體積比及縮短從外部到細胞中心的擴散距離，促
the diffusion of oxygen by increasing the surface area to 進氧氣的擴散。此外，這亦有助紅血球擠進狹窄的微血管，並得
volume ratio and shortening the diffusion distance from 以走遍全身。
outside to the center of the cell. Also, it allows RBC to
squeeze itself in order to travel through the narrow blood
capillaries all over the body.

References 參考資料： [5] Bratton DL, Henson PM. Neutrophil clearance: when the party
[1] Dupire J, Socol M, Viallat A. Full dynamics of a red blood cell in is over, clean-up begins. Trends Immunol. 2011;32(8):350-57.
shear flow. Proc Natl Acad Sci U S A. 2012;109(51):20808-20813. doi:10.1016/j.it.2011.04.009
doi:10.1073/pnas.1210236109 [6] Machlus KR, Thon JN, Italiano JE Jr. Interpreting the
[2] Smith DW. The molecular biology of mammalian hemoglobin developmental dance of the megakaryocyte: a review of the
synthesis. Ann Clin Lab Sci. 1980;10(2):116-22. cellular and molecular processes mediating platelet formation.
[3] Rosales C. Neutrophil: A Cell with Many Roles in Inflammation Br J Haematol. 2014;165(2):227-36. doi: 10.1111/bjh.12758
or Several Cell Types?. Front Physiol. 2018;9:113. doi:10.3389/ [7] de Back DZ, Kostova EB, van Kraaij M, van den Berg TK, van
fphys.2018.00113 Bruggen R. Of macrophages and red blood cells; a complex
[4] McCracken JM, Allen LAH. Regulation of human neutrophil love story. Front Physiol. 2014;5:9. doi:10.3389/fphys.2014.00009
apoptosis and lifespan in health and disease. J Cell Death. [8] Sukhbaatar N, Weichhart T. Iron Regulation: Macrophages in
2014;7:15-23. doi:10.4137/JCD.S11038 Control. Pharmaceuticals (Basel). 2018;11(4):137. doi:10.3390/
ph11040137

Based on the manga “Cells at Work!” by Akane Shimizu originally serialized in the monthly SHONEN SIRIUS magazine published by KODANSHA Ltd.
©Akane Shimizu / KODANSHA, Aniplex, davidproduction 13