CIBA FOUNDATION SYMPOSIUM ON CELLULAR ASPECTS OF IMMUNITY Editors for the Ciba Foundation G. E. W. TOLSTENHOLME, O.B.E., M.A., M.B., M.R.C.P. and MAEVE O’CONNOR, B.A. With 117 Illustrations LONDON J. & A. CHURCHILL LTD. 104 GLOUCESTER PLACE, W.l 1960 42 DISCUSSION is also phagocytosis of inert particles. We know that these inert particles are probably not influenced at all by the presence of com- plement, so there may be two kinds of process: a fundamental process of phagocytosis similar to this of inert particles where complement is not involved, and an immunological process where complement is certainly implicated. Robineaux: I tried to demonstrate some morphologically different processes of phagocytosis. I cannot say whether they are funda- mentally different, that is to say whether each of them involves a different mechanism at a molecular level or not. I think, as you do, that we could give all these phenomena the name of phagocytosis. As for the second point, it is generally admitted that complement is not necessary for phagocytosis to occur; however, it enhances the phagocytosis of particles which have previously fixed a specific anti- body. The phagocytosis of inert particles does not require comple- ment but it is known that some of the particles adsorb proteins which can thus modify their surface properties so that they are made adherent. liu?n$rey: The liver seems to be able to distinguish quite sharply between native and thermally altered proteins. We found evidence, bot.h in livers perfused in citro and in living rats, that there must be more than one mechanism involved in the uptake and subsequent catabolism of native and denatured material (Freeman, T., Gordon, A. H., and Humphrey, J. H. . &it. J. exp. Path., 39, 459). Dr. Robineaux, did you see labelled material in the nucleus of the cells, or was it entirely outside the nucleus? Robinemx: We never observed fluorescent material in the nuclei.