Lymphoproliferative Responses in Pigs Infected with Mycobacterium avium.

Abstract

ABSTRACT. Naturally infected cases of swine mycobacteriosis were divided into two groups, localized infection (LI) and disseminated infection (DI). Lymphoproliferative response (LPR) was then examined to estimate their immunological states. Both control and LI groups showed strong response to Concanavalin A (Con A) and phytohemagglutinin (PHA) in the LPR, and lymphocytes recovered from the LI responded well to purified protein derived from M. avium (PPD). On the other hand, the DI group showed weak response to both Con A and PHA, despite their strong response to PPD stimulation. These data suggest that the low LPR to Con A and PHA observed in the DI groups was probably not due to the general unresponsiveness of T-cells. KEY WORDS: lymphoproliferative response (LPR), Mycobacterium avium, swine.J. Vet. Med. Sci. 63(7): 827-829, 2001 Mycobacterium avium is widely distributed in the environment and is the causative agent of atypical mycobacteriosis in humans and animals [6,8]. In swine, most of the lesions are formed in the mesenteric or mandibular lymph nodes, and the disseminated lesions are occasionally observed in the liver, spleen, and lungs [3,5]. The organism apparently enters through the tonsils or the lining of the intestine, and then passes into the bloodstream through the portal circulation, subsequently causing miliary lesions in the liver and other organs [11]. Outbreaks of swine mycobacteriosis were detected at the Meat Inspection Centers of Japan. We found 13 cases of systemic infections among 1,588 pigs, which were diagnosed as having atypical mycobacteriosis. There is little knowledge about the immnopathological mechanism by which systemic infection occurs in only a few individuals and what factor (s) regulate the resistance or susceptibility to M.avium infection in pigs. It has generally been thought that suppression of cell-mediated immune function converts local tuberculous lesions into miliary tuberculosis, and that a decrease in the T lymphocyte population deteriorates the equilibrium of this disease. It has been reported that in vitro swine lymphocyte immunostimulation assay with purified protein derivative from M.avium (PPD) might be useful in the diagnosis of individuals with M.avium infection [1]. In the present study we examined the difference in cell-mediated immune responses in pigs with localized and systemic mycobacteriosis infections by evaluating the lymphoproliferative response (LPR) in order to certify the immune state.All pigs used in this investigation were two-or three-way crossbreeds (LWD) raised on commercial and conventional farms, and which were 6 months of age and about 100 kg in weight. The discovery and examination of M.aviuminfected individuals was performed at three Meat Inspection Centers in Miyazaki Prefecture. According to the severity of the disease, they were divided into two categories. The individuals in which tuberculous granuloma lesions were widely distributed in the liver and/or spleen were categorized as cases of disseminated infection (DI), whereas the p...

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“…These results demonstrate that there is an influence of the Rs infection on the CMI functions. Similar suppressive e#ect on the nonspecific T mitogenic response has previously been demonstrated in mammalian infections with Mycobacterium tuberculosis [29] and M. avium [30,31]. In the last mentioned study, as well as in the present study, a specific blastogenic lymphocyte response was demonstrated that suggested a partial insensitivity of T cells.…”

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“…No entanto, pode ocorrer infecção sistêmica, com lesões em órgãos como fígado, pulmões e baço (Iwakiri et al 2001, Matlova et al 2005, Hibiya et al 2008, Ingen et al 2010.…”