Because dendritic cells (DC) are the most potent antigen-presenting cells involved in many pathophysiological responses, we investigated the effect of chemokines on the migration of these cells in an effort to determine whether chemokines may contribute to the initiation of immune responses. CD34+ progenitor cells isolated from umbilical cord blood were grown in suspension cultures with cytokines and expanded 50- to 100-fold. A variable proportion of the cells expressed markers consistent with DC. The proportion of CD1a+ DC was increased when the cells were cultured with interleukin-4 (IL-4). These cells expressed specific binding sites for C-C and C-X-C chemokines. Cells cultured with or without IL-4 had similar binding profiles. All C-C chemokines tested, including monocyte chemotactic protein (MCP)-1, MCP-2, MCP-3, macrophage inflammatory protein-1 alpha (MIP1 alpha), MIP-1 beta, and RANTES, induced migration of DC-enriched cells cultured with or without IL-4 with MCP-3 being the most potent chemoattractant. Phenotypic analysis of cell migrating in response to C-C chemokines showed that CD1a+ cells were indeed attracted across the polycarbonate filters, and there was no preferential attraction of contaminating CD14+ monocytes by C-C chemokines. DC-enriched cells also expressed specific binding sites for IL-8 and NAP2, which failed to induce cell migration. Our results suggest that C-C chemokines may participate in the recruitment of DC to amplify host defense.
A 96-well-based suspension culture system for human hematopoietic progenitor cells has been developed to monitor the commitment and differentiation of CD34+ cells to specific lineages and the maintenance and expansion of CD34+ cells in vitro. The expression of maturation and lineage markers on the cells in culture was measured by enzyme-linked immunosorbent assay (ELISA). CD34+ cells were isolated from umbilical cord blood and fetal liver (90% purity) and were grown in liquid culture in 96-well plates for 10 days. The cells were then fixed with a glutaraldehyde-paraformaldehyde mixture, attaching the cells firmly to the plastic. An ELISA was performed, using appropriate primary antibodies directed against cell surface markers. The expression of four different lineage markers was measured: CD14 (monocyte), CD15 (neutrophil), platelet glycoprotein (GP) IIb/IIIa (CD41a, megakaryocyte) and glycophorin A (erythroid). The two-growth factor combination of interleukin 3 (IL-3) and stem cell factor (SCF) stimulated expression of CD14, CD15 and GP IIb/IIIa. Lineage-restricted growth factors such as erythropoietin (EPO), in combination with SCF, stimulated expression of glycophorin A. The three-factor combination of IL-3, SCF and EPO stimulated expression of all four lineage markers. Other multiple growth factor combinations all stimulated myeloid and megakaryocyte growth, as measured by ELISA and flow cytometry, but erythroid growth was present only when EPO was included in the growth factor mixture. In serum-free medium or plasma-containing medium, CD14 expression was markedly reduced, whereas glycophorin A expression was greatly elevated in serum-free medium.(ABSTRACT TRUNCATED AT 250 WORDS)
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.