Abstract:
Research in chickens has been fundamental for the discovery of basic aspects
of the immune system and has led to an interest in the in-depth characterization
of avian immune cell types including dendritic cells (DCs). The in vitro generation
and expansion of chicken bone marrow-derived DCs (chBMDCs) in the presence
of granulocyte-macrophage colony-stimulating factor (GM-CSF) has provided a way
to study chicken DCs, which are only present at limited cell numbers in vivo. This
method has been employed to study the interactions between chicken DCs and
pathogens or vaccines. However, a detailed characterization of the chBMDC culture
is still lacking. In the present study, we performed an elaborate phenotypical and
functional analysis of the chBMDC culture and addressed its heterogeneity. After 8 days
of culture, chBMDCs comprised major histocompatibility complex class II (MHC-II)low and
MHC-IIhigh subsets with different morphologies. Compared with MHC-IIlow chBMDCs,
the MHC-IIhigh subset showed a more mature phenotype, with higher expressions of
CD1.1, CD40, CD80, CCR7, and CD83, and a relatively low opsonophagocytic capacity.
Nevertheless, MHC-IIhigh chBMDCs did not show an increased capacity to induce
T-cell proliferation. Therefore, MHC-IIhigh chBMDCs were found to be semi-mature.
Interestingly, the presence of the semi-mature MHC-IIhigh chBMDC subset reduced
when cells were cultured in the presence of IL-4. Finally, prolonged cell culture after
fluorescence-activated cell sorting (FACS) converted the semi-mature MHC-IIhigh subset
back into the immature phenotype of the MHC-IIlow subset, demonstrating plasticity of
their maturation state. This detailed characterization explained the heterogeneity of the
chBMDC culture by the simultaneous presence of immature and semi-mature chBMDC
subsets, in addition to cells without features of antigen-presenting cells. Our findings
are instrumental for the interpretation of experiments using the chBMDC culture in past
and future research by providing insights into its phenotypically and functionally distinct
cell types.
