Published on June 29, 2023   22 min

Other Talks in the Series: The Immune System - key concepts and questions

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Hi everyone. I appreciate your interests in the lecture about phagocytosis. My name is Eileen Uribe-Querol, and I'm an Associate Professor at the School of Dentistry at the National Autonomous University of Mexico in Mexico City.
Here is an overview of our lecture. In this lecture, we will discuss the origins of phagocytosis. We will also define the concept of phagocytosis. We will review the different types of phagocytic cells and discuss the steps of the phagocytic process. The phagocytic steps are first, the recognition of the target particle, the activation of that internalization process, the phagosome formation, and finally, the phagosome moderation.
The first observations of phagocytosis. In the 19th century, Alexander Ecker, Nathanael Lieberkuhn, and Giulio Bizzozero, saw Erythrocytes inside cells. Ecker, saw them inside rabbit skin cells, Lieberkuhn saw them inside white blood cells, and Bizzozero inside macrophages. Sir William Osler, saw carbon particles inside cells too, while Robert Koch, Paul Albert Grawitz and Alexander Ogston, saw bacteria and fungi inside cells.
The origins of phagocytosis. In the 1880s, Elie Metchnikoff made his original observation while studying starfish larvae. He stuck rose thorns into starfish larvae. He was amazed that many special cells were attacking the small thorns. In his words, he said, if a delicate glass tube, a rose thorn or a spine of sea urchin may be introduced into one of these larvae, the amoeboid cells of the mesoderm collect around the foreign body, enlarge masses easily visible with the naked eye. Metchnikoff also published a paper describing the phagocytic process. In this publication, he used the word phagocyte from phago, that means eating, and cyte, that means cells. This term was adjusted to Metchnikoff, by his friend Carl Frederick William Gauss. Metchnikoff described the role of phagocytes during the metamorphosis of tadpole to frog and disappearance of the tail. He also described the process of phagocytosis against foreign microorganisms. Metchnikoff demonstrate that phagocytosis was mainly a function of little cells. Based on this observation, Metchnikoff realized phagocytosis was a defense mechanism. With great results, he moved into immunology and endorsed the concept of cellular immunity. He won the Nobel Prize in 1908.