title: Effect of secretory immunoglobulin A on bacterial translocation in an enterocyte-lymphocyte co-culture model.
abstract: Intestinal secretory immunoglobulin A (sIgA) plays an important role in gut mucosal immunity in vivo; however, in-vitro enterocyte models for studying the mechanisms of these effects are lacking. This study utilizes a cell-culture model to investigate the effect of sIgA on bacterial translocation (BT) across human enterocytes co-cultured with human lymphoid cells (Raji cells). This model is intended to mimic in-vivo enterocyte/lymphocyte interactions found in intestinal follicle-associated epithelia. Human Caco-2 enterocytes were grown to confluence on porous filters in the apical chamber of a two-chamber cell-culture system. After differentiation, human B lymphoid cells (Raji cells) were added to the basolateral surface of Caco-2 monolayers for 3 days' co-culture, followed by washing away of unincorporated Raji cells. Transepithelial electrical resistance (TEER) was used to measure tight-junction permeability. Monolayers were treated with or without sIgA, IgG (negative control), or mannose (positive control). BT across the cell monolayer was determined 1.5 h after addition of Escherichia coli. Statistical analysis was by the Kruskal-Wallis test, P below 0.05 considered significant. In co-culture monolayers treated with sIgA, IgG, or mannose, there was no significant effect on TEER; however, the magnitude of BT across cells treated with sIgA (1.3 +/- 0.4 log10CFU/ml) and mannose (1.6 +/- 1.1 log10CFU/ml) was significantly decreased compared to PBS (3.9 +/- 0.4 log10CFU/ml) and IgG (2.9 +/- 0.6 log10CFU/ml) controls (P < 0.05). sIgA BT inhibition was dose-dependent. BT inhibition by sIgA and mannose was additive (0.5 +/- 1 log10CFU/ml). Inhibition of BT was negated when sIgA and mannose were removed by washing prior to E. Coli addition (3.6 +/- 0.5 log10CFU/ml), suggesting that both inhibitors act through bacterial binding.
authors.affiliation: Section of Pediatric Surgery, University of Michigan, Mott Children's Hospital, Ann Arbor, MI 48109-0245, USA.
authors.forename: T
authors.initials: T
authors.lastname: Sawai
authors.forename: N
authors.initials: N
authors.lastname: Goldstone
authors.forename: R A
authors.initials: RA
authors.lastname: Drongowski
authors.forename: A G
authors.initials: AG
authors.lastname: Coran
authors.forename: C M
authors.initials: CM
authors.lastname: Harmon
mesh_terms: D018988:Bacterial Translocation / Q000187:drug effects* / Q000502:physiology; D018938:Caco-2 Cells / Q000187:drug effects / Q000502:physiology; D018929:Cell Culture Techniques; D002463:Cell Membrane Permeability / Q000502:physiology; D003126:Colostrum / Q000502:physiology; D017097:Electric Impedance; D020895:Enterocytes / Q000187:drug effects* / Q000502:physiology; D004926:Escherichia coli / Q000502:physiology*; D005260:Female; D006801:Humans; D007071:Immunoglobulin A, Secretory / Q000494:pharmacology*; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000502:physiology; D008214:Lymphocytes / Q000187:drug effects* / Q000502:physiology; D008358:Mannose / Q000494:pharmacology; D008954:Models, Biological; D011247:Pregnancy; D019108:Tight Junctions / Q000502:physiology
chemical_list: D007071:Immunoglobulin A, Secretory; D008358:Mannose