A subset of human CD34+ hematopoietic progenitors express low levels of CD4, the high-affinity receptor for human immunodeficiency virus-type 1.
We investigated the expression of CD4 antigen in normal bone marrow (BM) samples, enriched in CD34+ hematopoietic progenitor cells. At flow cytometry, a significant fraction (ranging from 25% to 65%) of CD34+ cells also showed low levels of CD4 antigen on their surface. The CD4 receptor densities on the surface of hematopoietic progenitors was approximately 50% that of peripheral blood monocytes and 5% of peripheral blood T lymphocytes. In immunoprecipitation experiments, the CD4 antigen expressed by BM hematopoietic progenitors appeared to be the same form expressed by mature peripheral blood CD4+ cells and appeared to be a potentially functional receptor for human immunodeficiency virus-type 1, because it specifically bound recombinant envelope gp120. Moreover, BM samples, highly enriched in CD34+ cells, showed the presence of CD4 mRNA at reverse transcription-polymerase chain reaction examination. In experiments of complement-mediated cytotoxicity with Leu3-a+Leu3b anti-CD4 monoclonal antibody, a significant reduction in the number of both classes of megakaryocyte (burst-forming unit-meg [BFU-meg] and colony-forming unit-meg [CFU-meg]) and granulocyte/macrophage (CFU-GM) progenitors was observed, whereas erythroid (BFU-E) progenitors were only slightly affected. Moreover, purified CD4+ BM cells obtained by immunomagnetic selection, using high concentrations of Leu3a+Leu3b, showed a colony-forming ability of megakaryocyte and granulocyte/macrophage progenitors comparable with that of CD4- BM cells. In conclusion, the present data show that immature hematopoietic progenitor cells express low levels of CD4, the high-affinity receptor of human immunodeficiency virus-type 1.
Zauli
G
G
Institute of Human Anatomy, University of Ferrara, Italy.
Furlini
G
G
Vitale
M
M
Re
M C
MC
Gibellini
D
D
Zamai
L
L
Visani
G
G
Borgatti
P
P
Capitani
S
S
La Placa
M
M
D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000032:analysis*; D018952:Antigens, CD34; D001483:Base Sequence; D001854:Bone Marrow Cells; D015704:CD4 Antigens / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D003165:Complement System Proteins / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006098:Granulocytes / Q000166:cytology; D015699:HIV Envelope Protein gp120 / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000276:immunology*; D006801:Humans; D008264:Macrophages / Q000166:cytology; D008533:Megakaryocytes / Q000166:cytology; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D012194:RNA-Directed DNA Polymerase; D011994:Recombinant Proteins / Q000378:metabolism
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018952:Antigens, CD34; D015704:CD4 Antigens; D015699:HIV Envelope Protein gp120; D012333:RNA, Messenger; D011994:Recombinant Proteins; D003165:Complement System Proteins; D012194:RNA-Directed DNA Polymerase