CELLULAR BASIS FOR IMMUNITY IN MALARIA 
241 
2. The littoral cells of Siegmund line the 
sinuses of the reticular tissues {e.g., the 
spleen, lymph nodes and bone marrow) 
and the sinusoids of the liver, hypophysis 
and adrenal. In the liver, they are known 
as Kupffer cells. Those of the reticular 
tissues are true reticular cells, but the 
exact nature of the littoral cells of the liver, 
hypophysis and adrenal is not sufficiently 
known although they are admittedly simi¬ 
lar to reticular cells. In any case, the sepa¬ 
ration of the littoral cells from the previous 
category is convenient as they behave some¬ 
what differently because they are located 
along the blood stream. It is unfortunate 
that they are still frequently termed endo¬ 
thelial cells and are grouped with true 
endothelial cells because the latter are more 
limited in their potencies for phagocytosis 
and development. An accurate, but con¬ 
fusing, custom is to group the littoral cells 
under the designation special endothelium 
as contrasted with true endothelium. 
The littoral cells of the liver and to a 
lesser extent of the other organs are func¬ 
tional in immunity to malaria. 
3. The fixed, outstretched, undifferenti¬ 
ated cells of Maximow in the adventitia of 
the small blood vessels of loose connective 
tissue throughout the body have broad 
mesenchymal potencies. They are widely 
distributed over the body, but are only 
incidentally functional in malarial immun¬ 
ity. Thus, after intense malarial stimu¬ 
lation, pericytes in the dense periportal 
connective tissue (Glisson’s capsule) of the 
liver are phagocytic for malarial material. 
Whenever the blood vessels are occluded 
with resulting hemorrhage, they are phago¬ 
cytic and because of their location are fre¬ 
quently erroneously considered to be true 
endothelial cells. 
4. The macrophages, variously known as 
histiocytes (Aschoff and Kiyono), elas- 
matocytes (Ranvier), resting wandering 
cells (Maximow) and rhagiocrine cells 
(Renaut), comprise about half of the cells 
in the loose and dense connective tissue 
throughout the body. As in the case of the 
perivascular cells they phagocytose ma¬ 
larial material only incidentally. Thus, 
the macrophages of the skin are active 
when infected blood is introduced intra- 
dermally and they join with the perivascu¬ 
lar cells of the loose connective tissue in 
phagocytosing malarial material during 
vascular occlusion in various organs. The 
nature of the phagocytes or glial cells, 
which are similarly active in the brain, is 
not entirely clear. 
(2) Fibroblasts and endothelial cells. 
Fibroblasts which, together with the 
macrophages, are the chief cellular con¬ 
stituents of loose and dense connective tis¬ 
sue generally assume a functional role in 
the later stages of defense. They repair 
connective tissue, fill in cavities and wall 
off foreign material that cannot be removed 
by phagocytosis. They can proliferate by 
mitosis. A few investigators, especially v. 
Mollendorff (for a discussion and criticism 
of this work, see Maximow 1927a, 1927b; 
Bloom 1938b), believe that they, like some 
of the macrophages, are endowed with full 
mesenchymal potencies, but most workers 
consider them highly differentiated in man 
and believe that they are rarely phago¬ 
cytic and do not generally develop into 
other cells. In lower animals, however, as 
for example during repair and regenera¬ 
tion of the spleen after malarial infarction 
and necrosis in the canary, they can trans¬ 
form into reticular cells with full mesen¬ 
chymal potencies for development. It is 
possible that under exceptional conditions 
such ordinarily latent potencies may be 
invoked in man. 
The role of the fibroblasts in malarial 
immunity is probably limited to connective 
tissue repair, the filling in of cavities and 
scarring, all of which are associated with 
infarction and similar injuries seen most 
frequently in infections with P. falciparum. 
The endothelial cells, as designated in 
this chapter, are sharply differentiated 
from the littoral cells and are restricted to 
the cells which line the larger blood vessels 
and capillaries. They, like the fibroblasts, 
have only limited capacities for defense 
under ordinary conditions. Thus, they can 
proliferate by mitosis, are only rarely 
phagocytic and do not generally develop 
into other cells. 
In malaria the endothelial cells assume 
