The immune responses in actinomycetoma lesions caused by Streptomyces somal
iensis in Sudan were characterized by immunohistochemistry during 1997-1998
. In sections stained with haematoxylin and eosin, the inflammatory reactio
n around the grain was of 2 types. In type I there were 3 zones: a neutroph
il zone immediately around the grain, an intermediate zone containing mainl
y macrophages, and a peripheral zone consisting of lymphocytes and plasma c
ells. Zone 1 stained positively for CD15 (neutrophils), zone 2 for CD68 (ma
crophages) and CD3 (T lymphocytes), and zone 3 for CD20 (B lymphocytes). In
the type II reaction, there was no neutrophil zone, the grains being surro
unded only by macrophages and giant cells. This was confirmed by immunohist
ochemistry, which demonstrated the presence of CD3 positive cells. Immunogl
obulins G and M and complement were demonstrated on the surface of the grai
n and on filaments inside the grain. Neutrophils and macrophages were recru
ited into the lesion by complement and were involved in the fragmentation o
f the grain. The cytokine profile in the lesion and regional lymph nodes wa
s of a dominant Th2 pattern (interleukins-10 and 4).