In vertebrate animals, pleural and peritoneal cavities are repositories of milky spots (MS), which constitute an
organised coelom-associated lymphomyeloid tissue that is intensively activated by
Schistosoma mansoni
infection.
This study compared the reactive patterns of peritoneal MS to pleural MS and concluded from histological analysis
that they represent independent responsive compartments. Whole omentum, lungs and the entire mediastinum of
54
S. mansoni-infected mice were studied morphologically. The omental MS of infected animals were highly
activated, modulating from myeloid-lymphocytic (60 days of infection) to lymphomyeloid (90 days of infection) and
lymphocytic or lymphoplasmacytic (160 days of infection) types. The non-lymphoid component predominated in the
acute phase of infection and was expressed by monocytopoietic, eosinopoietic and neutropoietic foci, with isolated
megakaryocytes and small foci of late normoblasts and mast cells. Nevertheless, pleural or thoracic MS of infected
mice were monotonous, consisting of small and medium lymphocytes with few mast and plasma cells and no myeloid
component. Our data indicate that compartmentalisation of the MS response is dependent on the lymphatic vascu-
larisation of each coelomic cavity, limiting the effects or consequences of any stimulating or aggressive agents, as
is the case with
S. mansoni infection.
