Dendritic cell Development in the Neonatal Intestine

Dendritic cells (DCs) are crucial for the ability of the intestinal immune system to decide between inducing tolerance or active immunity. We and others have identified four populations of intestinal DCs based on CD11b and CD103 expression, with CD103⁺CD11b⁺ DCs being unique to the intestine. As this suggests the presence of specific differentiation factors in the local microenvironment, here we have explored when this population appears during early life. All four DC subsets are present in the lamina propria (LP) from birth, but CD103⁺CD11b⁺ DCs are scarce at this time and do not reach adult levels until around weaning. This is not simply due to delayed expression of CD103, as there is parallel acquisition of TREM-1 expression by this subset of DCs. A similar pattern of subset maturation is seen amongst migratory DCs in the draining mesenteric lymph node (MLN), although this is delayed compared with LP, consistent with these cells arriving from the mucosa. Thus the profound changes that occur in the intestinal environment after birth appear to be responsible for the selective differentiation of CD103⁺CD11b⁺ DCs and identification of the factors involved will aid understanding of how DCs assist induction of tolerance against commensal bacteria and food proteins.