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Phenotype and function of a CD56+ peripheral blood monocyte
G Sconocchia1, K Keyvanfar, F El Ouriaghli
1Stem Cell Allotransplantation Section, Hematology Branch, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
Leukemia
|November 5, 2004
Summary
Researchers identified a rare CD56-low, CD33+ monocyte population in peripheral blood that resembles cells grown in vitro. These monocytes exhibit unique functional properties, potentially serving as a normal counterpart to myeloid/natural killer cell leukemia.
Area of Science:
- Immunology
- Cell Biology
- Hematology
Background:
- Granulocyte-colony stimulating factor (G-CSF) primed CD34 cells cultured with IL-2 and stem cell factor generate CD56(high) natural killer (NK) cells and a novel adherent CD56(low) CD16- population expressing myeloid markers.
- This study investigated the presence of similar CD56(low)CD33+ cells in peripheral blood.
Purpose of the Study:
- To identify and characterize a circulating CD56(low)CD33+ monocyte population in normal individuals.
- To compare the immunophenotypic and functional characteristics of these peripheral blood cells with in vitro-cultured cells.
- To explore their potential role as a normal counterpart to hybrid myeloid/natural killer cell leukemia.
Main Methods:
- Flow cytometry was used to identify and quantify CD56(low)CD33+ cells in peripheral blood mononuclear cells (PBMNCs) from 13 healthy individuals.
- Immunophenotyping included markers such as CD33, HLA-DR, FcgammaRI, FcgammaRII, CD11b, and CD14.
- Functional assays assessed T-lymphocyte proliferation induction (upon cytomegalovirus antigen priming), T-cell proliferation in HLA-mismatched settings, antiproliferative effects on K562 cells (with and without LPS stimulation), and cytokine production (IL-6, IL-1beta).
Main Results:
- A circulating population of CD56(low), CD33+, FcgammaRI+, FcgammaRII+, HLA-DR+, CD11b(high), CD14+ monocytes was found in all 13 normal individuals, closely resembling the cultured CD56(low)CD33+ cells.
- These monocytes constituted a mean frequency of 1.3+/-1% (range 0.16-3.5%) of total mononuclear cells.
- CD56(low)CD33+ cells induced autologous T-lymphocyte proliferation comparable to CD56- CD14+ peripheral blood monocytes (PBM) and showed enhanced T-cell proliferation in HLA-mismatched conditions.
- They exhibited a low antiproliferative effect on K562 cells, which increased upon LPS stimulation, and produced detectable levels of IL-6 and IL-1beta.
Conclusions:
- A distinct minor monocyte population with unique phenotypic and functional characteristics exists in human peripheral blood.
- These CD56(low)CD33+ monocytes may represent a normal counterpart to the rare CD56+ CD33+ hybrid myeloid/natural killer cell leukemia.
- The findings contribute to understanding myeloid-derived suppressor cells and their role in immune regulation and disease.