Histol Histopath (1 992) 7: 421-425 Histology and Histopathology Kupffer cells and PlMs in acute experimental African Swine Fever L. Carrasco, A. Fernández, J.C.Gómez Villamandos, E. Mozos, A. Méndez and A. Jover Department of Histology and Pathology, Faculty of Veterinary, University of Córdoba, Córdoba, Spain Summary. An ultrastructural study of Kupffer cells and pulmonary intravascular macrophages (PIMs) of healthy and African Swine Fever (ASF)-infected pigs was carried out. A vascular perfusion method was performed in order to obtain an optimal intravascular morphology and tissue fixation. The infection developed acute ASF lesions in both organs. Both Kupffer cells and PIMs were studied at different stages of infection. The differences observed in both macrophagic cells from uninfected and infected tissues are shown and discussed. Key words: African Swine Fever, Kupffer cells, Pulmonary intravascular macrophages lntroduction The origin of Kupffer cells is still controversial. Like other macrophages, there is good evidence that Kupffer cells arise from bone marrow monocytes (Lloyd and Triger, 1975). However, when there is a local demand in the mature liver, there is good evidence of local proliferation as well as extrahepatic recruitment (Bouwens et al., 1984, 1986). Kupffer cells are clearly in a strategic position to clear the portal blood strearn of bacteria and endotoxins, of viruses and immune complexes, and of thromboplastins and fibrin complexes that might appear in disseminated intravascular coagulation (DIC) (Wardle, 1987). Pulmonary intravascular macrophages (PIMs) are mature mononuclear phagocytic cells that inhabit the pulmonary capillaries of certain mammalian species (Winkler, 1988). Offprint requests to: Dr. L. Carrasco, Departamento de Histologia y Anatomía Patológica, Facultadde Veterinaria, Universidadde Córdoba, Córdoba, Spain Probably, they originate from undifferentiated monocytes, which perinatally colonize lung capillaries. Postnatally, proliferating monocytes are junctionally attached to capillary endothelium, and differentiate into phagocytic intravascular macrophages (Winkler and Cheville, 1985, 1987; Winkler, 1988). It has been established that intravascular macrophages are the principal sites of pulmonary retention of substantial numbers of blood cells, blood borne bacteria and particulates in pigs, calves, sheeps, goats and cats (Rybicka et al., 1974; Crocker et al., 1980, 1981; Bertram, 1986; Warner and Brain, 1986; Warner et al., 1986). Clasically, the uptake of blood-borne particles has been shown to be carried out in the spleen, liver and lung. However, the lung containing PIMs seems to be central in this role (Crocker et al., 1980, 1981; Niehaus et al., 1980; Warner and Brain, 1986; Warner et al., 1986, 1987). The 75 - 80 per cent of P. aurinigm is retained in the lung when it is inoculated intravenously into pigs (Dehring and Wismar, 1989). Equally, the pig's lung retains more blood-borne bacteria than spleen and liver in infections with Staphilococcus spp. (Dehring et al., 1983). African Swine Fever (ASF) is a haemorrhagic disease of domestic pigs caused by an intracytoplasmic deoxyvirus at present classified as a member of the Iridoviridae (Almeida et al., 1967; Enjuanes et al., 1976). The virus replicates primarilv in cells of the mononuclear phagoc-yte syst&m (MPS) (Maurer et al., 1958). he central pathology is the development of thrombocytopenia, haemorrhage and circulatory disturbance which results in oedema, extravasation of fluid, shock and death (Anderson, 1986; Anderson et al., 1987). 1n the present work the morphological changes observed in both cells, Kupffer cells and PiMs, at different stages of ASF infection will be shown.