852 IMMUNOLOGY 



acquired resistance to P. cathemerium, but, even when pushed to the 

 maximum, does not affect natural resistance. This work, however, is open 

 to the possible criticism that the large amounts of pigment in the macro- 

 phages after the crisis, which are not there before the development of 

 immunity, may simply augment the blockading doses to produce the 

 observed effect. In the third place, as pointed out previously, accumulat- 

 ing evidence indicates that the greatly superior mechanism for disposing 

 of parasites associated with acquired immunity is highly specific and is 

 probably associated with an antibody. 



The limitation of phagocytosis to the macrophages of the spleen, liver, 

 and bone marrow is probably a question of opportunity, as such macro- 

 phages are advantageously placed where they can remove material from 

 the blood stream. The so-called general immunity in malaria, therefore, 

 is actually a local reaction in strategically placed organs (W. H. Talia- 

 ferro, 1934). It should be noted, however, that in overwhelming infec- 

 tions the parasites may be so numerous that secondary complications, such 

 as stasis of the blood, clogging of the capillaries, and hemorrhage may 

 occur in various organs. In such an event the macrophages of the brain, 

 lungs, suprarenals, and kidneys, as well as those of the bone marrow, 

 liver, and spleen, may actively phagocytose malarial material. 



CAPTION FOR PLATE ON FACING PAGE 



Plate 3. Portions of a venous sinus and Billroth cords in the spleen of an uninfected 

 rhesus monkey (Fig. 1) and comparable portions from a rhesus monkey during the late 

 acute rise of an infection with Plasmodium cynomolgi (Fig. 2). X l400. (From W. H. 

 Taliaferro and H. W. Mulligan, "Histopathology of Malaria with Special Reference to 

 the Function and Origin of the Macrophages in Defence," Indian Medical Research 

 Memoirs, No. 29 ([May, 1937], pp. 1-138.) 



Figure 1. The normal constituents of the venous sinus are chiefly the cells of the 

 circulating blood (lymphocytes, granulocytes, and red cells), and those of the Billroth 

 cords are also cells of the circulating blood with a greater proportion of large lymphocytes 

 and, in addition, reticular cells with indeterminate cytoplasm and slightly phagocytic 

 macrophages. 



Figure 2. The additional constituents of the venous sinus and of the Billroth cords in 

 the spleen of a monkey during the late acute rise of an infection of P. cynomolgi are 

 parasitized red cells and many transitional cells (polyblasts) between lymphocytes and 

 macrophages, containing malarial pigment. The progressive hypertrophy of lymphocytes 

 into macrophages is shown by nuclear changes and by increased amounts of cytoplasm in 

 the lymphocytes (see especially Med Lym 1, which also contains two small granules of 

 malarial pigment) and by further nuclear changes, increased size, and increased phagocytic 

 activity in the polyblasts (see especially polyblasts 1 through 5). Throughout this tran- 

 sitional series, phagocytosis increases approximately with the size of the cell. 



