Biomedical subjects

D M Liberati

Publications and source records attributed to D M Liberati.

7 recordsLinked to original sources

PubMed2001

Sequential changes in mucosal immunity after hemorrhagic shock.

Immunoinflammatory responses after shock and major trauma are characterized by an early hyperinflammatory response and later by compensatory anti-inflammatory host mediator production. This late phase is associated with depressed immune function that has been causally linked with post-traumatic infectious complications and late organ failure. Gut barrier failure is noted in this setting and may be an important source of nosocomial infections and organ failure. Secretory immunoglobulin A (sIgA) is the predominant immunoglobin at mucosal surfaces and is difficult to quantify in luminal secretions. Attempts to normalize sIgA concentrations may not be accurate and/or may not be applicable in vivo. A method using mucosal immunization with cholera toxin (ChT) to normalize gut sIgA levels was used to assess serial changes in sIgA after hemorrhagic shock (HS) in rodents. Total and anti-ChT sIgA levels were highly variable in both HS and sham animals. However, when normalized using the specific anti-ChT/total sIgA ratio, differences were clearly evident. This ratio was depressed between 3 and 10 days post-HS. The specific anti-ChT/total sIgA ratio is a reliable index of secretory antibody at gut luminal surfaces. Impaired mucosal immune function occurred in a time frame consistent with development of late nosocomial infections. This may be important mechanistically in the development of these infectious complications.

Animals↗

PubMed1999

Synergistic effect of hyperoxia and immunoglobulin A on mucosal barrier defense.

BACKGROUND: Hyperoxia has been reported to be protective against gut-derived sepsis. Although secretory immunoglobulin A (IgA) is primarily responsible for humoral defense of mucosal surfaces, a potential synergistic effect with hyperoxia is unknown. An asanguineous cell monolayer system was used to study these aspects in vitro. METHODS: MDCK cells were grown as polarized monolayers in a two-chamber culture system. Apical chambers were inoculated with 10(8) Escherichia coli M14 with or without polyclonal IgA and incubated in a 21 or 95% O2 environment. Basal medium was sampled at 90 and 180 minutes for bacterial translocation. In a second experiment, MDCK cells were lysed at 90 minutes and intracellular bacteria were quantitated. RESULTS: Bacterial translocation was decreased versus normoxia by the treatment groups IgA without hyperoxia or IgA with hyperoxia at 90 minutes. Bacterial internalization at 90 minutes was reduced to the greatest extent by the combined effects of hyperoxia and IgA. Translocation data at 180 minutes confirmed the additional protective effect of hyperoxia with IgA. CONCLUSION: Hyperoxia exerts a significant protective effect on barrier function independent of enhanced leukocyte function. Hyperoxia has an added effect to the mucosal defense provided by IgA.

Aerobiosis↗

PubMed1999

Synergistic effects of Candida and Escherichia coli on gut barrier function.

BACKGROUND: Disruption of the indigenous gut microflora with overgrowth of gram-negative bacteria and Candida species is common in the critically ill patient. These organisms readily translocate in vitro, which may cause septic complications and organ failure. A synergistic effect between Escherichia coli and C. albicans in polymicrobial infections has been demonstrated. An interaction between these organisms at the mucosal barrier is unknown. METHODS: Ca(CO2) monolayers were grown to confluence in a two compartment culture system. E. coli and C. albicans or E. coli alone were added to the apical chambers. Secretory immunoglobulin A was added to half of the apical chambers as well. Cell cultures were incubated for a total of 240 minutes. Basal media were sampled at timed intervals for quantitative culture. Monolayer integrity was confirmed by serial measurement of transepithelial electrical resistance. RESULTS: Secretory immunoglobulin A decreased bacterial translocation across Ca(CO2) monolayers challenged with E. coli alone. Transepithelial passage of E. coli was significantly increased by coculture of bacteria with C. albicans. Augmentation of bacterial translocation by Candida occurred even in the presence of secretory immunoglobulin A. CONCLUSIONS: Candida colonization of the GI tract may impair mucosal barrier defense against gram-negative bacteria. The clinical role of gut antifungal prophylaxis in protecting against gut derived gram-negative sepsis is speculative.

Bacterial Translocation↗

PubMed1999

Hemorrhagic shock impairs mucosal immunity to gut-derived antigens.

Secretory immunoglobulin A (sIgA) is the principal antibody protecting against pathogens in the respiratory tract and other mucosal surfaces. Nosocomial pneumonias are frequent after injury and critical illness and are often due to enteric pathogens. The aim of this study was to assess the relative effect of hemorrhagic shock (HS) on mucosal immunity at intestinal and respiratory mucosal sites. Fisher rats were immunized intragastrically with dinitrophenylated (DNP) Pneumococcus (Pn). Three weeks later, animals were subjected to sham treatment or HS. The animals were then rechallenged with DNP-Pn 1 or 3 days later. Animals were sacrificed 7 days later, and bronchoalveolar and gastric lavage was performed. Total and anti-DNP-specific sIgA were quantitated from these secretions by enzyme-linked immunosorbent assay. There was a significant decrease in DNP-Pn-specific sIgA at 72 hours after HS, which was not present in animals at 24 hours after HS. This was most profound in bronchoalveolar lavage specimens. We conclude that impaired mucosal defense against gut-derived antigens after HS may be important mechanistically for the development of posttraumatic pneumonia and other mucosally related infectious complications.

Animals↗

PubMed1998

The effects of bacterial overgrowth and hemorrhagic shock on mucosal immunity.

Impairment in systemic and mucosal immune function is noted after hemorrhagic shock (HS). Overgrowth of gut microflora is common after shock insults and may act as a reservoir for intensive care unit-acquired infections and subsequent remote organ failure. Secretory immunoglobulin A (IgA), the principle immunoglobulin in intestinal secretions, is the first line of defense of mucosal surfaces. Although HS and gut bacterial overgrowth are often temporarily related, their combined effect on IgA is unknown and served as the basis for this study. After sham or HS, self-filling blind loops (SFBL) were created to affect bacterial overgrowth. Intestinal secretions were obtained 7 days later from SFBL and jejunal segments for quantitative culture. Gut washings were also obtained and secretory IgA levels determined by enzyme-linked immunosorbent assay. Bacterial overgrowth in the SFBL was associated with significant increases in IgA levels in the sham group only. IgA levels were depressed in both jejunal and SFBL segments in the HS group. Impaired humoral mucosal defense may be important mechanistically in the development of nosocomial infections and organ failure after HS, particularly with concurrent gut bacterial overgrowth.

Animals↗

PubMed1997

An in vitro model to assess mucosal immune function and bacterial translocation.

The importance of secretory immunoglobulin A (IgA) on intestinal barrier function has gained increasing acceptance. However, due to the complexity of the intestinal microenvironment, the relative role of secretory IgA (sIgA) in mucosal defense has been difficult to study in vivo. Polarized Madin-Darby canine kidney (MDCK) epithelial cells expressing the complementary DNA (cDNA) for the polymeric Ig receptor were grown as monolayers in an in vitro two-chamber cell culture system to study the impact of sIgA on bacterial translocation (BT). Polymeric sIgA or media alone was added to the apical chambers of cell monolayers followed by apical inoculation with bacteria. The basal compartment was sampled at timed intervals thereafter to determine BT. Bacterial passage across the MDCK epithelial cell monolayers occurred in a time and bacterial inoculum concentration gradient. Addition of sIgA led to significant reductions in BT across the epithelial cell monolayers. This is a useful model for further investigation on the role of sIgA in intestinal barrier function.

Animals↗

PubMed1997

Secretory immunoglobulin A blocks hypoxia-augmented bacterial passage across Madin-Darby canine kidney cell monolayers.

OBJECTIVE: To study the relative impact of previous hypoxic exposure and the addition of secretory immunoglobulin A (IgA) on bacterial translocation. DESIGN: In vitro randomized experimental study. MATERIALS AND METHODS: Transfected Madin-Darby canine kidney epithelial cells were grown as monolayers in a two-chamber tissue culture system. Stationary growth phase Escherichia coli M14 were inoculated in the apical chamber with medium or medium containing polymeric secretory IgA. Tissue culture dishes were then placed in a 21 or 5% O2 incubator environment for 90 minutes followed by a 21% O2 environment. Medium from the basal compartment was then obtained at timed intervals for bacterial culture. MEASUREMENT AND MAIN RESULTS: Bacterial translocation increased with time in co-culture. Previous hypoxic exposure augmented translocation across the monolayers. The addition of IgA blocked translocation under both normoxic and hypoxic conditions. CONCLUSION: Secretory IgA is important in mucosal defense under both normal and shock conditions.

Animals↗