Omental and pleural milky spots: different reactivity patterns in mice infected with Schistosoma mansoni reveals coelomic compartmentalisation

Abstract

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 vascularisation of each coelomic cavity, limiting the effects or consequences of any stimulating or aggressive agents, as is the case with S. mansoni infection

Fat-associated lymphoid clusters control local IgM secretion during pleural infection and lung inflammation

“…Upon immune challenge, these structures support rapid activation of serous B cells and germinal center formation 13 15 . The existence of similar lymphoid structures has been reported in the adipose deposits of the pleural cavity, the mediastinum 13 16 17 18 and the pericardium 13 . Although the density of FALCs in pericardium and mediastinum is high 13 , the functional role of these clusters has not been investigated.…”

Milky spots: omental functional units and hotbeds for peritoneal cancer metastasis

“…Capillaries with high density and different levels constituted the basic skeleton of MS within the internal layer. Other H&E staining researches [ 11 , 27 , 42 , 46 , 47 ] found similar results that these purple cellular clusters stained by hematoxylin constitute MS together with pink blood vessels stained by eosin. However, immune cells could not be differentiated into specific types for further studies only by H&E staining.…”

“…Pleural and peritoneal cavities are repositories of MS [ 27 ]. In pleural cavity, MSs seem to be located mainly in the pleural fold behind the pericardium rather than lung parenchyma [ 27 ]. However, MS can be found in many tissues in abdomen pelvic cavities.…”

Lack of galectin-3 up-regulates IgA expression by peritoneal B1 lymphocytes during B cell differentiation

“…During schistosomiasis, peritoneal cells react against S. mansoni antigens (Panasco et al 2010). The peritoneal cavity is a reservoir of circulating leukocytes, including monocytes, T and B lymphocytes and granulocytes frequently detected attached in the omentum and mesentery (Carlow et al 2009;Lenzi et al 1996).…”