LPS-mediated triggering of T lymphocytes in immune response against gram-negative bacteria

Impairment of phagocytic and T-cell-mediated antibacterial activity and plasma endotoxins in patients with untreated gastrointestinal cancer

BACKGROUND

Cancer patients have multiple immune deficits, and mediators, such as prostaglandins, transforming growth factor-beta, and interleukin (IL)-10, may play a role in the pathogenesis of these immune dysfunctions.

METHODS

Fifty-six patients with gastrointestinal cancer (11 gastric cancer, 7 papilla of Vater cancer, and 38 colorectal cancer) were enrolled for this study, before starting conventional treatments. Phagocytosis and killing exerted by polymorphonuclear cells and monocytes, peripheral blood mononuclear cell absolute numbers, T-cell-mediated antibacterial activity, serum levels of IL-10 and interferon (IFN)-gamma, and plasma bacterial endotoxin concentration were evaluated.

RESULTS

Data show an impaired phagocytic and T-cell-mediated antibacterial activity in all cancer patients, whereas only in subjects with gastric cancer were IFN-gamma serum levels reduced. Circulating endotoxins were detected in 17 patients.

CONCLUSIONS

In untreated gastrointestinal cancer patients the capacity of phagocytes and T-cells to clear pathogens is reduced. This dysfunction may increase the risk of becoming infected and may account for the presence of endotoxin in 30% of patients.

Murine epidermal V gamma 5/V delta 1-T-cell receptor+ T cells respond to B-cell lines and lipopolysaccharides

The V gamma 5/V delta 1(+)-T-cell receptor (TCR)-bearing T-cell clone, 2CBET-3, was generated from C57BL/6 mice. Upon stimulation, 2CBET-3 cells produce interleukin (IL)-3, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor-alpha, but not IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, macrophage colony-stimulating factor, or interferon-gamma. These cells were evaluated for their ability to be stimulated by a variety of murine cell lines, including fibroblasts, trophoblasts, melanoma cells, embryonic carcinomas, B-cell lymphomas, mastocytoma cells, and keratinocytes. The human B-lymphoma cell line, Daudi, also was included in these studies. We found that 2CBET-3 cells produced cytokines up to several hundredfold above the control levels in response to the B-cell lines, Daudi, and A20/2J, but not to the B-cell line 439.4.2. After fixation with glutaraldehyde, Daudi and A20/2J continued to stimulate this gamma delta T-cell line. 2CBET-3 cells also responded to the keratinocyte line PAM212, but not to another, XB-2. When lipopolysaccharides (LPS) from Escherichia coli or S. typhimurium were added to 2CBET-3 cells in the presence of A20/2J cells, 2CBET-3 cells responded with increased cytokine production compared with the cytokine production in the presence of A20/2J cells alone. 2CBET-3 cells by themselves did not respond to LPS alone or to supernatants from A20/2J cells incubated with LPS. Unlike 2CBET-3, the epidermal T-cell hybridoma 70BET-49, expressing a V gamma 5/V delta 1-TCR identical to that of 2CBET-3, did not respond to A20/2J cells in the presence or absence of LPS, suggesting a requirement for molecules other than the TCR for V gamma 5/V delta 1-TCR+ T-cell stimulation by the B-cell lines and by LPS. This unique reactivity of gamma delta-TCR+ cells is different from that of alpha beta-TCR+ cells and may reflect a functional specialization of gamma delta-TCR+ cells in the response to bacterial infections.

Downregulation of human polymorphonuclear cell activities exerted by microorganisms belonging to the alpha-2 subgroup of Proteobacteria (Afipia felis and Rochalimaea henselae)

Intracellular pathogens have evolved effective mechanisms in order to survive in an intracellular environment, thus avoiding destruction by phagocytic cells. In this regard, a correlation between resistance to phagocytic killing and expression of pathogenic potency has been established. In this report, we have studied the interaction between human polymorphonuclear cells (PMN) and two gram-negative microorganisms, Afipia felis and Rochalimaea henselae, which belong to the alpha-2 subgroup of the class Proteobacteria. A. falis has been previously proposed as the causative agent of Cat Scratch Disease (CSD), but several recent lines of evidence attribute a major role to R. henselae. Of note, CSD is a syndrome characterized by a chronic lymphoadenopathy, involving macrophages and endothelial cells with a progression towards a granulomatous process and/or angiogenesis. Since members of the alpha-2 subgroup of Proteobacteria have the property to survive intracellularly, we have evaluated the effects exerted by A. felis and R. henselae on human PMN in terms of chemotaxis locomotion, degranulation and oxidative metabolism. Results will show an impairment of PMN activities as a consequence of the challenge with both microrganisms. In particular, inhibition of PMN oxidative function occurred either as result of a direct exposure to both A. felis and R. henselae or when PMN were primed by bacteria for the N-formyl-methionyl-leucyl-phenylalanine enhancement of the oxidative burst. These findings may account for the ability of A. felis and R. henselae to survive within PMN as expression of a further mechanism of pathogenic potency, influencing also the nature and the evolution of inflammatory response in the lesion sites.

Effectiveness of thymostimulin and study of lymphocyte-dependent antibacterial activity in children with recurrent respiratory infections

Recurrent respiratory infections (RRI) consist of more relapsing acute respiratory infections than the ones expected for the age [> 6 acute respiratory tract infections (RTI) per year if age is > 3 years, and > 8 acute RTI per year if age is < 3 years]. Concerning the pathogenesis of RRI, several investigations report the important role of environmental factors, early socialization and immunological dysfunctions, such as lymphocyte subpopulations alterations, IgG subclass deficiency and phagocytosis and/or opsonization deficit during acute infections. In this framework, we have studied the lymphocyte-dependent antibacterial activity (ABA) among 121 children affected by RRI. Results show a statistically significant alteration of this function in 38 children (31.4%): 19 of them exhibited an absent ABA (group 1), while in the others same function was reduced (group 2). A bovine thymic extract, thymostimulin, was administered to both groups by intramuscular injections (1 mg/kg) for a 3 month cycle. At the end of therapy we observed a statistical significant rise of ABA only in group 1 and among children aged > 3 years. Among the same patients, 33 children (86.8%) improved in terms of reduction of clinical score and better results were seen among children aged > 3 years. These data emphasize the beneficial role of thymostimulin in RRI-affected children, suggesting a transient immaturity of the immune system as one of the possible pathogenetic factor.

Studies on the epidemiology of child infections in the Bari area (south Italy). VII. Epidemiology of Epstein-Barr virus infections

Serological patterns against Epstein-Barr virus (EBV) specific antigens were determined in 3732 healthy babies and children aged 0-10 years living in the Bari area (South Italy). IgG antibodies against EBV capsid antigen (VCA) were found in 2713 subjects (72.7%). Seropositivity rates, high in the first semester of life (83.8%), declined between 6 and 12 months (65.6%) and even further between 1 and 2 years (43.8%). After 2 years the frequency of positive children rose progressively reaching steady levels between 5 and 7 years (80.2%) and between 8 and 10 years (81.9%). IgA antibodies against VCA, IgG anti-early viral antigen (EA) and IgG against virus-associated nuclear antigens (EBNA) were found in 17.9%, 15.9% and 25.7% of the subjects tested, respectively. IgM anti-VCA were found only in 35 (0.9%) children, but 818 (21.9%) exhibited antibody patterns suggestive of a recent infection: IgG anti-VCA > or = 1:160 alone or in association with IgA anti-VCA or IgG anti-EA or both. These results suggest that in this area the primary infection by EBV occur early in life, with immunity to EBV acquired primarily after 4 years.