Despite being a major organ of the immune system, the spleen's role in
resisting, controlling or simply ameliorating nematode infections has
been neglected. A review of both filarial and gastrointestinal nemato
des suggests that though it is difficult to fully assess or quantify t
he organ's importance in vivo, the spleen is prominent in acting again
st nematode parasites in mammals. One manifestation of this is that tr
ansfer of lymphocytes from the spleen of immunised individuals can pro
tect recipients against the disease. Expansion of splenic lymphoid tis
sue also alludes to its activity during nematode infection. There is a
considerable need for investigation of the spleen under natural condi
tions as well as much more rigorously controlled experiments even in m
ammals besides birds and other vertebrates.