Murine Ia antigens for the I-A and I-E/C subregions were detected on mouse granulocyte-macrophage progenitor cells (CFU-GM). An association was established betwen the expression of these Ia antigenic determinants on CFU-GM during DNA synthesis and the regulatory action of acidic isoferritins in vitro. Treatment of bone marrow cells of the correct haplotype with monoclonal anti-Ia antibodies for the I-A or I-E/C subregions with complement (C) inhibited colony and cluster formation by ~50%. Similar treatment with monoclonal anti-H-2K antibodies plus C reduced colony and cluster formation by 95 to 100%. The capacity to detect inhibition with anti-Ia plus C depended on the source of conditioned medium used to stimulate colony formation, as well as the source of C used or the cytotoxicity assays. Sources of granulocyte-macrophage colony-stimulatory factors (GM-CSF) containing high levels of inhibitory acidic isoferritins did not allow detection of Ia antigens on CFU-GM. Using GM-CSF free of acidic isoferritins, reduction of colonies and clusters was similar whether bone marrow cells were exposed to anti-Ia plus C, high specific activity tritiated thymidine (3HTdr), or acidic isoferritins. No further decrease was apparent with 3HTdr or acidic isoferritins after Ia antigen-positive CFU-GM were removed, or with anti-Ia plus C or acidic isoferritins after S-phase CFU-GM were removed. Anti-Ia without C did not reduce colony or cluster formation, but did block the inhibitory action of acidic isoferritins, an effect not blocked by monoclonal anti-H-2K antibodies. These results indicate that mouse CFU-GM express Ia during S-phase of the cell cycle, and that it is these Ia-positive cells that are sensitive to regulation by acidic isoferritins.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of Immunology|
|State||Published - Jan 1 1982|
ASJC Scopus subject areas
- Immunology and Allergy