406 BIOLOGY OF PNEUMOCOCCUS 



the injection of specific immune serum, Meyer argued that the ef- 

 fect of these measures could not be due to a decrease in the phago- 

 cytic activity of the reticuloendothelial cells, but rather to an in- 

 hibition of antibody formation in the cells and that active as well 

 as passive immunity depended upon specific antibodies circulating 

 in the blood and present in the cells. The contribution of the re- 

 ticulo-endothelial system to the operation of the immune mecha- 

 nism was believed by Wright (1927) 1547 to be of relatively slight 

 importance. Although he acknowledged that the possibility of a 

 residual cellular immunity could not be overlooked, Wright con- 

 sidered circulating antibodies to be the prime factor in immunity 

 to Pneumococcus. 



The relationship of blood-free splenic cells of normal and im- 

 munized rabbits was investigated by Loewenthal and Micseh 

 (1929). 822 Using the technique of tissue culture devised by the 

 first-named author, it was found that the macrophages of the 

 spleen of normal rabbits phagocyted avirulent pneumococci only 

 in the presence of fresh, normal serum, and phagocyted virulent 

 organisms only in the presence of specific immune serum. Macro- 

 phages of the spleen of immunized rabbits phagocyted both aviru- 

 lent and virulent pneumococci without the addition of either nor- 

 mal or immune serum, when the tissue fragments were not trans- 

 planted into a fresh medium. However, when bits of spleen tissue of 

 immunized rabbits were transplanted into fresh media during tis- 

 sue culture, the macrophages behaved similarly to those of normal 

 animals. Loewenthal and Micseh believed that the results pointed 

 to a close relation between the mechanisms of humoral and cellular 

 immunity. 



In 1932 and 1933, Kritschewski, Rubinstein, and Heronimus 758 ' 9 

 confirmed the results of Meyer on the inability of antipneumococ- 

 cic serum to protect mice that had been splenectomized and had 

 suffered artificial impairment of function of the reticuloendo- 

 thelial system. The great majority of mice so treated succumbed 

 to intraperitoneal inoculation with Type I Pneumococcus. 



