Inflammation is a hallmark of brucellosis. Although Brucella abortus, one of the disease’s etiologic agents, possesses cytokine-stimulatory properties, the mechanism by which this bacterium triggers a proinflammatory response is not known. We examined the mechanism whereby heat-killed B. abortus (HKBA), as well as its LPS, induces production of inflammatory cytokines in monocytes/macrophages. Polymyxin B, a specific inhibitor of LPS activity, did not inhibit the production of TNF-α- and IL-6-induced HKBA in the human monocytic cell line THP-1. HKBA induced the production of these cytokines in peritoneal macrophages of both C3H/HeJ and C3H/HeN mice, whereas B. abortus LPS only stimulated cells from C3H/HeN mice. Anti-TLR2 Ab, but not anti-TLR4 Ab, blocked HKBA-mediated TNF-α and IL-6 production in THP-1 cells. Because bacterial lipoproteins, a TLR2 ligand, have potent inherent stimulatory properties, we investigated the capacity of two B. abortus lipoproteins, outer membrane protein 19 (Omp19) and Omp16, to elicit a proinflammatory response. Lipidated (L)-Omp16 and L-Omp19, but not their unlipidated forms, induced the secretion of TNF-α, IL-6, IL-10, and IL-12 in a time- and dose-dependent fashion. Preincubation of THP-1 cells with anti-TLR2 Ab blocked L-Omp19-mediated TNF-α and IL-6 production. Together, these results entail a mechanism whereby B. abortus can stimulate cells from the innate immune system and induce cytokine-mediated inflammation in brucellosis. We submit that LPS is not the cause of inflammation in brucellosis; rather, lipoproteins of this organism trigger the production of proinflammatory cytokines, and TLR2 is involved in this process.

No abstract

Food allergy is becoming a medical, economical and social problem. Soybean, together with milk, peanuts and eggs, are the major allergenic foods. This pathology affects the infant population, when the gut barrier is immature and the immune system is still refining its ability to tolerate food proteins. In our country, cow's milk allergy (CMA) constitutes the main food allergy in infancy, but soy allergy has become exacerbated because of the increased utilization of soy-based formulas as cow's milk (CM) substitutes and the inclusion of soy-proteins in many processed foods. Once a food allergy is diagnosed, the only proven therapy is the strict elimination of the offending allergens from the diet. Available substitutes for CM include milks from different mammalian animals, soy-based formulas, hydrolysed cow's milk proteins (CMP) and amino acid-based formulas. Furthermore, there is evidence that soy proteins may trigger allergic reactions in CMA patients, as assessed by a double-blind placebo controlled food challenge (DBPCFC) [1].Milk contains more than 50 proteins and the major ones are implicated in a number of immunologically mediated reactions [2]. Caseins and b-lactoglobulin (b-Lg) have been described as the main antigenic and allergenic components for human beings [3,4], although immunoglobulins, a-lactalbumin (a-La), and bovine serum albumin (BSA) were also found to be reactive with different isotypes of human antibodies [5,6]. Several immunoreactive epitopes have been identified in caseins [7,. Most of the epitopes present in the casein molecules are sequential since the high number of proline and hydrophobic residues (45%) in these proteins determine an undefined secondary and tertiary structure [10]. Besides, caseins tend to aggregate as a result of hydrophobic interactions to give quaternary structures [11], and this may create conformational epitopes buried in the hydrophobic interior of the micelle [7]. These epitopes are only exposed and accessible to the immune system after denaturation of the complex by digestion.A number of soy proteins that bind antibodies, especially IgE, have been identified [12,13]. The main fractions of storage globulins from seed proteins are the complexes 7S or b-conglycinin, and 11S or glycinin. The 7S complex is generally a trimer with MW 150-200 kD, whereas 11S is a hexamer with MW 300-400 kD [14]. In the 7S fraction, or b-conglycinin, several IgE-binding proteins have been identified and some of them have been purified and characterized: Gly m Bd 28K, Gly m Bd 30K, Gly m Bd 60K [15,16]. Sequence homology has been reported between these allergens and the thiol proteinase family SUMMARYSoy-based formulas are the most employed cow's milk substitutes in the treatment of cow's milk allergy in our country. Since adverse reactions have been reported in allergic patients as a consequence of exposure to soy proteins, we have investigated the possible cross-reactivity between components from soybean and cow's milk. A cow's milk specific polyclonal antiserum and casein specific m...