Page 16 - 《渔业研究》2025年第5期

第 5 期 何暮春等： 贝类血淋巴细胞及其增殖、分化和死亡 557

The mollusc hemocytes and their proliferation, differentiation, and death

*
HE Muchun，YU Hong，WANG Jie，SUN Jiejie ，SONG Linsheng *
(Liaoning Key Laboratory of Marine Animal Immunology and Disease Control, Liaoning Key Laboratory of Marine Animal
Immunology, School of Marine Science and Environment Engineering, Dalian Ocean University, Dalian 116023, China)

Abstract: [Objective] This paper describes the structural and functional characteristics as well as current clas-
sification of mollusc hemocytes, and summarizes the molecular mechanisms governing their proliferation, dif-
ferentiation, and death. These insights will enhance the systematic understanding of mollusc immune cells and
their fate determination, offering valuable support for future research in mollusc immunology. [Progress]
Hemocytes, as the primary immune cells in mollusks, exhibit considerable diversity and complexity in their
morphology, function, classification, proliferation and differentiation pathways, as well as modes of cell death.
Significant variations exist in the overall cellular morphology and the content of intracellular organelles and
granules among hemocytes from different mollusks, reflecting their functional diversity and adaptability. Hemo-
cytes are crucial in defending against pathogenic invasion, primarily through phagocytosis, the synthesis and se-
cretion of immune active substances. During phagocytosis, a respiratory burst occurs, catalyzing the production
of various reactive oxygen intermediates (ROIs) that kill pathogens engulfed within the cells. Beyond direct
pathogen defense, hemocytes also participate in tissue repair and the maintenance of immune homeostasis.
Based on cellular morphology and functional characteristics, mollusc hemocytes are mainly classified into three
types: agranulocytes, semigranulocytes, and granulocytes. Agranulocytes typically lack distinct granular struc-
tures and can participate in wound repair; semigranulocytes contain a small number of granules and possess cer-
tain phagocytic and bactericidal capabilities; granulocytes, on the other hand, are rich in granules that store vari-
ous bactericidal substances and enzymes. These three types of hemocytes collaborate to form a complex im-
mune defense system in molluscs. The proliferation, differentiation and death of hemocytes represent a com-
plex and dynamic process involving the interaction of multiple molecules and the regulation of various signal-
ing pathways. Regarding proliferation, hemocytes are regulated by multiple transcription factors, growth factors,
and cytokines. During differentiation, hemocytes can differentiate into various types of immune cells under spe-
cific microenvironments and molecular regulation to meet different immune demands. Hemocytes undergo vari-
ous forms of programmed cell death, including apoptosis, pyroptosis, autophagy, ferroptosis, and cuproptosis.
The proliferation, differentiation, and death of hemocytes play crucial roles in the immune defense and mainten-
ance of immunological homeostasis in molluscs. [Prospect] Although significant progress has been made in
the research on mollusc hemocytes, there still remain numerous challenges. To address the complexities of their
structure, function and classification, advanced techniques are needed to establish a unified and scientific classi-
fication system. Furthermore, systems biology approaches integrating multi-omics data should be utilized to re-
construct the molecular regulatory networks governing hemocyte proliferation and differentiation. In terms of
cell death, the mechanistic differences in the various types of cell death in molluscs are compared and the inter-
relationships among different forms of cell death are clarified. Integrating these findings on cell death with the
established hemocyte classification and regulatory networks will be instrumental in systematically elucidating
the fate-determination mechanisms of various immune cells. These fundamental theoretical advances will not
only enhance our understanding of the evolution and mechanisms of the mollusc immune system but also
provide crucial theoretical support for the prevention and control of diseases in mollusc aquaculture.
Key words: mollusc; hemocytes; cell classification, structure, and function; cell proliferation and differentia-
tion; cell death