IgA gene expression and quantification of cecal IgA+, IgM+, and CD4+ cells in chickens treated with EFAL41 and infected with Salmonella Enteritidis

IgA gene expression and quantification of mucous IgA+, IgM+ and CD4+ lymphocytes in the cecum of chicks was studied by qRT-PCR, immunohistochemistry and flow cytometry. A total of 220 1-day-old Salmonella-free chicks of Cobb 500 were divided into four groups (n = 55). Group 1 served as control (C), group 2 was pretreated with probiotic bacterial strain Enterococus faecium AL41 (EFAL41), group 3 was infected with Salmonella Enteritidis PT4 (SE), and group 4 was pretreated with E. faecium AL41 and subsequently challenged with Salmonella Enteritidis PT4 (EFAL41 + SE). The relative mRNA expression of IgA was upregulated in the EFAL41 group (P < 0.05) when compared to control group at 4 dpi. In comparison to the control, EFAL41 and SE group, the relative mRNA expression of IgA was also upregulated in EFAL41 + SE group at 7 dpi (P < 0.001). Immunohistochemistry revealed, that the density of IgA+ cells was higher in EFAL41 + SE group comparing to the controls and SE groups (P < 0.001). Significantly more CD4+ cells were present in the SE group than in EFAL41 (P < 0.05), and EFAL41 + SE groups (P < 0.001) at 4 dpi. In contrast, higher density of CD4 + cells at 7 dpi was seen in EFAL41 + SE group as compared with controls (P < 0.05). Flow cytometry determined that relative percentage of intraepithelial lymphocytes (IEL) IgA+ cells was higher in EFAL41 than in SE and EFAL41 + SE groups (P < 0.05). Comparing to controls the number IgM+ cells increased in SE group (P < 0.05) at 7 dpi. The results demonstrated beneficial effect of E. faecium AL41 on the mRNA expression of IgA and number of IgA+ cells. Lamina propria lymphocytes (IgA+, IgM+) were not affected by EFAL41 intake or salmonella infection. Probiotic bacterial strain EFAL41 positively influenced the number of IEL during the first days of infection.