36 3.79 ± 0.02 ΔSPI4 4.83 ± 1.42 5.60 ± 1.36 2.97 ± 1.75 ΔSPI5 3.52 ± 1.79 4.29 ± 2.32 2.90 ± 1.40 SPI1o 0.33 ± 0.47* 0.33 ± 0.47* 2.20 ± 1.59 SPI2o 5.29 ± 0.87 5.82 ± 1.07 3.76 ± 0.77 SPI3o 0.00 ± 0.00* 0.00 ± 0.00* 0.33 ± 0.47* SPI4o 0.00 ± 0.00* 0.00 ± 0.00* 1.68 ± 2.38 SPI5o 0.00 ± 0.00* 0.00 ± 0.00* 1.07 ± 1.51* ΔSPI1-5 0.00 ± 0.00* 0.00 ± 0.00* 1.06 ± 1.50* * T-test different at P < 0.01 from the mice infected with the wild type S. Enteritidis Next we were interested to what extent the different virulence of individual SPI mutants would be reflected in host immune responses. Since the cell-mediated

immune response is important for the protection against S. enterica and lymphocytes play an important role in the co-ordination of the host’s immune response, we first characterised changes in lymphocyte subpopulations after the infection with the wild type strain and all the SPI mutants. When 3 mice from each group

were Momelotinib molecular weight sacrificed on day 5 post infection i.e. before the onset of fatalities, no differences in the distribution of splenic B-lymphocytes, CD3 T-lymphocytes and γδ T-lymphocytes were observed. Of the Th lymphocytes, the only statistically significant change was the Go6983 purchase decrease in number of CD4 lymphocytes observed after the infection with the SPI2o mutant when compared with the non-infected mice. CD4 lymphocytes also decreased in number after the infection with the ΔSPI1 mutant, i.e. another mutant in which, similarly to the SPI2o mutant, SPI-1 was absent while SPI-2 was present, although in selleck compound this case the decrease did not reach statistical significance (P = 0.0634, see also Table 2). However, we did not investigate this further because we found another lymphocyte subpopulation which exhibited a more pronounced changes which also correlated with the severity of the infection (see below). Table 2 Two-colour flow cytometry of splenic CD3 and Monoiodotyrosine CD19 T- and B-lymphocytes, CD4 and CD8 T-lymphocytes, and γδ T-lymphocytes in mice infected with S. Enteritidis 5 days post-infection.   CD3+19- CD19+3- CD19-3- CD4+8+ CD4+8- CD4-8+ γδT wt 52.5 ± 0.76 41.8 ± 2.07 5.4 ± 1.33* 1.4 ± 0.33 31.1 ± 2.93 14.8 ± 0.28

0.93 ± 0.09 ΔSPI1 57.1 ± 6.50 39.6 ± 5.80 3.2 ± 0.98* 0.9 ± 0.10 24.5 ± 6.26& 16.2 ± 2.05 0.50 ± 0.08 ΔSPI2 50.3 ± 3.77 41.8 ± 2.91 7.7 ± 0.98 1.1 ± 0.13 27.4 ± 1.80 14.5 ± 0.35 0.80 ± 0.22 ΔSPI3 55.1 ± 3.26 40.9 ± 4.37 3.9 ± 1.59* 1.4 ± 0.33 27.1 ± 4.63 16.4 ± 1.19 0.53 ± 0.05 ΔSPI4 56.5 ± 4.24 39.5 ± 3.61 4.1 ± 1.42* 1.3 ± 0.46 26.8 ± 2.80 16.2 ± 1.05 0.67 ± 0.24 ΔSPI5 60.1 ± 5.22 35.8 ± 4.05 3.9 ± 1.25* 1.1 ± 0.21 33.8 ± 1.01 14.9 ± 1.33 0.57 ± 0.05 ΔSPI1-5 55.5 ± 3.07 36.4 ± 2.86 8.0 ± 1.79 2.1 ± 0.41 34.6 ± 3.01 17.2 ± 0.26 0.70 ± 0.08 SPI1 only 55.6 ± 3.78 37.4 ± 2.54 7.1 ± 1.75 0.9 ± 0.26 35.0 ± 3.44 16.1 ± 0.70 0.97 ± 0.05 SPI2 only 43.0 ± 2.50 49.0 ± 6.63 3.8 ± 2.02* 0.6 ± 0.25 23.8 ± 5.80* 14.4 ± 1.16 0.80 ± 0.22 SPI3 only 62.7 ± 4.28 29.9 ± 4.46 7.5 ± 0.49 1.4 ± 0.05 29.2 ± 2.92 18.6 ± 0.87 0.80 ± 0.16 SPI4 only 64.2 ± 4.33 28.