A Contribution to the Study of the Opsonins

Through the researches of Wright and Douglas 1 it has been established tha t the phagocytic effect of human leucocytes upon certain bacteria is essentially dependent upon the presence in the blood plasma and serum of substances which they have termed opsonins. They could demonstrate tha t these substances per se are to a certain extent at least thermolabile, being part ly destroyed by heating the blood serum to a temperature of 6o65 ° C. for ten minutes or more. The phagocytic effect of such serum is accordingly diminished and may indeed be suspended. If, however, bacteria are first digested with normaI serum and subsequently exposed to a temperature of 6o-65 ° C. phagocytosis proceeds in a normal manner. The organisms ir~ question are the staphylococci, Bacillus pestis, Micrococcus melitensis, Diplococcus pneumonim (Fr~nkel), Bacillus coli, Bacillus dysenterim, Bacillus anthracis, Bacillus typhosus, Bacillus tuberculosis and the vibrio of Asiatic cholera, while the diphtheria bacillus and Bacillus xerosis were found to be insensible to opsonic action. With the latter phagocytosis proceeds as promptly with heated as with unheated serum. In a series of further studies Wright and his collaborators then illustrate the variations in the opsonic content of the blood in certain infections and discuss the significance of the data obtained from the standpoint of immunity. The therapeutic inferences to which they are led and the practical results which