XX. ON THE NATURE OF OPSONINS * 



BY J. G. SLEESWIJK (Leyden). 



In a previous article I have reported some experiments bear- 

 ing on the function of the so-called opsonins in cellular immunity.! 

 I demonstrated a thermolabile substance in frog serum which 

 appears indispensable for phagocytosis of the anthrax bacillus. 



I have since continued my studies on this subject for the purpose 

 of answering the familiar question: Are the opsonins individual 

 substances sui generus, or are they identical with known immune 

 bodies? I may refer to a few of the many publications on opsonins 

 which are of particular importance in this connection. 



It may be stated at once that my work has led to the conclusion 

 that the non-specificity or, better, non-autonomy of the opsonins 

 seems to me fully established. 



The subject, indeed, is far from new. Metchnikoff and his pupil 

 Bordet in his studies on preventive sera,J and later Savtchenko 

 with hemolysis, and indeed all investigators that have worked with 

 antisera, have noted their favoring influence on phagocytosis. 

 The explanations of this influence have, however, varied: some 

 have thought that the bacteria are prepared for the action of 

 an intracellular or an extracellular alexin by specific sensitizers, 

 whereas Metchnikoff assumes the existence of stimulins with a 

 direct influence on the leucocytes. || 



For a long time attempts have been made to find specific sub- 

 stances which act as intermediaries between bacteria and phagocytes, 

 since we know that there are preventive sera which have not the 



* Ueber den Bau der Opsonine. Cent, f., Bakt., I. Orig., XLVI, 1908, 513. 

 t Annales de 1'Institut Pasteur, December, 1907. 

 J On the mode of action of preventive sera, p. 81. 

 Savtchenko. Annales de 1'Institut Pasteur, 1902. 



II Contrary to the opinion of certain investigators (Sauerbeck, Leishman), 

 Metchnikoff still supports hie stimulin theory. Compare Lubarsch and Ostertags' 

 Ergebnisse, 1907. 



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