Expression of Macrophage Inflammatory Protein-1a Receptors in Human CD341 Hematopoietic Cells and Their Modulation by Tumor Necrosis Factor-a and Interferon-g

Macrophage inflammatory protein-1a (MIP-1a) can stimulate growth inhibitory and potent chemotactic functions in hematopoietic cells. To investigate whether the action of MIP-1a may be regulated at the cellular receptor level, we studied the expression and modulation of MIP-1a receptors on CD341 cells isolated from normal bone marrow (NBM), umbilical cord blood (CB), and leukapheresis products (LP). Expression of MIP-1a receptors on CD341 cells was analyzed by two-color flow cytometry using a biotinylated MIP-1a molecule. The mean percentage of LP CD341 cells expressing the MIP-1a receptors was 67.7 6 7.2% (mean 6 SEM; n 5 22) as compared with 89.9 6 2.6% (n 5 10) and 74.69 6 7.04% (n 5 10) in CB and NBM, respectively (P 5 .4). The expression of the MIP-1a receptor subtypes on LP CD341 cells was studied by indirect immunofluorescence using specific antibodies for the detection of CCR-1, CCR-4, and CCR-5. Microscopical examination revealed a characteristic staining of the cytoplasmic cell membrane for all three receptor subtypes. Detailed analysis of two LP samples showed that 65.8%, 4.4%, and 30.5% of CD341 cells express CCR-1, CCR-4, and CCR-5, respectively. Culture of LP CD341 cells for 24 to 36 hours in the presence of tumor necrosis factor-a (TNF-a) and interferon-g (IFN-g) resulted in a significant increase in MIP-1a receptor expression. TNF-a induced MIP-1a receptor upregulation in a timeand concentration-dependent manner. Our results suggest that inhibitory cytokines produced by the bone marrow microenvironment are likely to be involved in the regulation of MIP-1a receptor expression on hematopoietic cells. r 1998 by The American Society of Hematology.