Esteban M A, Meseguer J
Department of Cell Biology, Faculty of Biology, University of Murcia, Spain.
Anat Rec. 1994 Dec;240(4):589-97. doi: 10.1002/ar.1092400416.
The ultrastructure of the phagocytic process in fish has not been established in spite of the significant morphofunctional differences detected in the fish immune system with respect to the basic immunological pattern in vertebrates. We report the ultrastructure of the bacterial phagocytic defence mechanism in sea bass (Dicentrarchus labrax L.).
Head-kidney, blood, and peritoneal exudate leukocytes were challenged with Aeromonas salmonicida and Escherichia coli and processed for transmission electron microscopic study.
Macrophages challenged with bacteria showed changes in the cell outline, in the chromatin pattern, and in the ultrastructural features of the cytoplasm as a consequence of an activation process. The phagocytic process consists of the following: 1) Bacteria-macrophage contact. One or more spot contacts between the bacterial wall and the phagocyte membrane are observed. 2) Bacteria engulfment. Slight depressions, membrane invaginations, or cytoplasmic processes are formed at the phagocyte surface. Macrophage processes occasionally surround the bacteria, overlapping and roaming parallel, or a single, long pseudopod encircles a bacterium several times. 3) Endocytic vesicle formation. Macrophages show one or more bacteria inside membrane-bound cytoplasmic vesicles. 4) Phagolysosome formation. Some dense granules (lysosomes) fuse with the endocytic vesicle. 5) Intracellular killing/digestion. Bacteria inside the endocytic vesicles are observed both virtually intact or damaged at different digestion stages.
Sea bass macrophages possess the mechanisms necessary to both engulf and kill bacteria. Cellular and subcellular events in the morphology of phagocytosis and lysosomal dissolution of bacteria fit the general pattern described for mammals.
尽管鱼类免疫系统在基本免疫模式方面与脊椎动物存在显著的形态功能差异，但鱼类吞噬过程的超微结构尚未明确。我们报告了海鲈（Dicentrarchus labrax L.）细菌吞噬防御机制的超微结构。
用杀鲑气单胞菌和大肠杆菌攻击头肾、血液和腹腔渗出液白细胞，并进行透射电子显微镜研究。
受到细菌攻击的巨噬细胞由于激活过程而在细胞轮廓、染色质模式和细胞质超微结构特征方面发生变化。吞噬过程包括以下步骤：1）细菌与巨噬细胞接触。观察到细菌壁与吞噬细胞膜之间有一个或多个点状接触。2）细菌吞噬。吞噬细胞表面形成轻微凹陷、膜内陷或细胞质突起。巨噬细胞突起偶尔围绕细菌，相互重叠并平行游动，或者单个长伪足多次环绕细菌。3）内吞小泡形成。巨噬细胞在膜结合的细胞质小泡内显示一个或多个细菌。4）吞噬溶酶体形成。一些致密颗粒（溶酶体）与内吞小泡融合。5）细胞内杀伤/消化。在内吞小泡内的细菌在不同消化阶段观察到几乎完整或受损。
海鲈巨噬细胞具备吞噬和杀死细菌所需的机制。吞噬作用形态学和细菌溶酶体溶解中的细胞及亚细胞事件符合哺乳动物所描述的一般模式。
