FACTORS DETERMINING PHAGOCYTOSIS 315 



Average 

 Phagocytosis 



Human leukocytes (washed in NaCl solution) -f- Streptococcus 300 .... 1 . 

 Human leukocytes (washed hi NaCl solution) + Streptococcus (treated 



with human serum) 14 . 



Human leukocytes (washed in NaCl solution) + Streptococcus (treated 



with guinea pig serum) 12 . 



Human leukocytes (washed in NaCl solution) -f- Streptococcus (treated 



with rabbit serum) 14 . 



Wright and Douglas' 15 work was done at first with normal 

 serum or normal citrate plasma, and in this case they found that the 

 opsonins were essentially unstable, being easily weakened by ex- 

 posure to light, or heat, and even when preserved in sealed tubes in 

 the dark they diminished noticeably on standing for 5 or 6 days. 

 Other writers who have worked with the opsonic substances in nor- 

 mal serum have confirmed this instability of the normal opsonin, 

 although even Wright himself admits that heating to 60 C. does 

 not entirely destroy the opsonic power, though it reduces it to a 

 minimum. A protocol from Wright and Douglas' first paper will 

 best illustrate the degree of reduction of opsonic power resulting 

 from the exposure of normal serum to 60-65 C. for 10 to 15 minutes. 



A. Unheated serum Wright Staphylococcus suspension 1 vol. Blood cells 



Wright 3 vols. 



(1) Phagocytic average 20 cells 17 .4 



(2) Phagocytic average 20 cells 19.8 



B. Heated serum as above. 



(1) Phagocytic average 52 cells 0.6 



(2) Phagocytic average 46 cells 3.4 



The experiments just cited refer only to the opsonic powers of 

 normal serum. When an animal is immunized with any particular 

 micro-organism or other cellular antigen, such as red blood cells, 

 etc., a marked specific increase of opsonins occurs, but unlike the 

 opsonins of normal serum these newly formed elements in the im- 

 mune serum seem to possess a much greater resistance to heat. 



Neufeld and Rimpau, 16 who have studied these constituents of 

 immune serum with especial thoroughness, have shown that heating 

 to 62 to 63 C. for as long as three-quarters of an hour does not 

 destroy them, and that such sera may be preserved for as long as 

 several years without their complete disappearance. 17 



We may accept as definitely determined, therefore, that there is 

 a qualitative difference between the serum components which initiate 

 phagocytosis in normal serum (normal opsonins) and those which 

 carry out the same function to a much more powerful degree in 



is "Wright and Douglas. Cited in Wright, "Studien iiber Immun., etc.," 

 p. 9. 



16 Neufeld and Rimpau. Deutsche med. Woch., No. 40, 1904; Zeitschr. 

 f. Hyg., Vol. 51, 1905. 



17 Leishman. Trans. London Path. Soc., Vol. 56, 1905. 



