The Effects of Salmonella typhimurium on Intestinal Dendritic Cells

Dendritic cells (DCs) trigger the adaptive immune response. In the intestinal lamina propria (LP) this process begins with antigen uptake and subsequent migration of DCs to the mesenteric lymph nodes (MLN). DCs from the LP and MLN are defined as CD64^- B220^- CD11c⁺ MHC II^hi cells and can be further subdivided into 4 functionally-different DC subsets, based on their expression of CD11b and CD103. We aimed to characterise the mechanisms enabling Salmonella typhimurium (STM) to reach the MLN, and to discover whether DCs are responsible for transporting bacterial antigens during STM infection. To allow efficient STM colonisation we pre-treated animals with streptomycin (ABX). Our results show that CX3CR1^- and CX3CR1^int DCs but not CX3CR1^hi cells migrate to the MLN before and after STM infection. Preliminary data indicate that all DCs subsets continue to migrate effectively to the MLN after STM infection, albeit mice that received ABX + STM showed higher proportion of total MLN DCs, with a lower frequency of CD11b⁺ CD103^- DCs and more CD103⁺ CD11b^- DCs, compared to mice receiving STM only. Our next aim is to establish, by collecting lymph from the thoracic duct of STM-infected mice, which migrating cells are responsible for transporting STM to the MLN.