Investigating myeloid development in the context of a spleen microenvironment

The spleen contains multiple myeloid cell populations with varying functions in immunity and wound
healing. The differentiation of hematopoietic stem cells (HSC) and progenitors into myeloid
CD11b+
CD11clo antigen presenting cells (APC) has been previously demonstrated in vitro in the
context of a spleen stromal microenvironment. This same subset is also produced indefinitely in
spleen long-term cultures (LTC), suggesting they represent a spleen endogenous immune cell
population derived from tissue-resident HSC. However, the precise correlation between culturederived myeloid APC and naturally-occurring APC in spleen has been difficult to establish, although
they are clearly distinct from conventional dendritic cells. This study now addresses whether common
monocyte progenitors (CMoP) differentiate to give this distinct subset of myeloid CD11b+
CD11clo APC
in the context of a spleen stromal microenvironment, and whether these represent monocytes or a
unique cell lineage. Findings will be presented demonstrating in vitro spleen stromal co-cultures of
CMoP from sources including adult bone marrow, and adult and neonatal spleen. Co-cultures of HSC
over spleen stroma, and cytokine-induced (SCF, LIF, IL-3 and IL-6) cultures of CMoP, will serve as
controls which produce myeloid CD11b+
CD11clo APC and CD11b+
Ly6Chi monocytes, respectively.
Results from this study specifically allow the establishment of a relationship between co-culture and
LTC-derived myeloid-APC, and cells arising from the monocyte lineage defined by the CMoP
precursor.