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Commitment of juvenile myelo-monocytic (JMML) leukemic cells to spontaneously differentiate into dendritic cells
Daniela Longoni1, Giovanna D'Amico, Giuseppe Gaipa
1Clinica Pediatrica-Università degli Studi di Milano-Bicocca, Osp. San Gerardo-Monza, Italy. longonid@libero.it
Abstract:
Juvenile myelo-monocytic leukemia (JMML) is a severe malignant stem cell disorder of childhood. A proportion of cells from JMML mononuclear cells (MNC) spontaneously differentiate in vitro into dendritic cells (DC). We have studied MNC from 14 JMML patients, and characterized their functional activity as antigen presenting cells (APC). Large cells, differentiated after seven days of culture, expressed high levels of MHC II molecules and Mannose Receptor, variable levels of CD80 and CD86, and low levels of CD1a. Similar to immature DC, cells from JMML had high levels of dextran endocytosis, and were able to elicit proliferation of allogeneic T lymphocytes in mixed leukocyte reaction (MLR). CD40L-matured DC from JMML was associated with relevant increase of CD80, CD86 and CD83, increased APC activity, responded in chemotaxis assays to MIP-3beta and secreted increased amounts of macrophage derived chemokine (MDC). Immature DC and CD40L-matured DC from JMML produced very low amounts of IL-12, whereas the production of IL-10 was higher than normal DC. In line with these findings, they showed defective capacity to polarize naive T cells to differentiate into Th1 effectors. These results indicate that MNC from JMML are committed to spontaneously differentiate into DC with morphological and phenotypical characteristics similar to normal DC. The cytokine profile produced by these APC is likely to suppress and not to elicit a protective immune response.
Insights
Juvenile myelo-monocytic leukemia (JMML) cells can differentiate into dendritic cells (DC) that function as antigen-presenting cells (APC). However, these JMML-derived APCs produce an immune-suppressive cytokine profile, hindering protective immune responses.
Area of Science:
- Immunology
- Hematology
- Pediatric Oncology
Background:
- Juvenile myelo-monocytic leukemia (JMML) is a serious childhood stem cell disorder.
- A subset of JMML cells spontaneously differentiate into dendritic cells (DC) in vitro.
- Understanding the function of these JMML-derived DCs is crucial for comprehending disease pathology.
Purpose of the Study:
- To characterize the functional activity of antigen-presenting cells (APC) derived from JMML mononuclear cells (MNC).
- To investigate the immunophenotype and cytokine production of JMML-derived DCs.
- To assess the capacity of JMML-derived DCs to polarize T cell responses.
Main Methods:
- Culturing MNC from 14 JMML patients to allow spontaneous differentiation into DC.
- Characterizing cell surface markers (MHC II, Mannose Receptor, CD80, CD86, CD1a, CD83) using flow cytometry.
- Assessing APC function via mixed leukocyte reactions (MLR) and measuring cytokine production (IL-12, IL-10, MDC) and chemotaxis (MIP-3beta).
Main Results:
- JMML-derived cells differentiated into DC with high MHC II and Mannose Receptor expression, similar to immature normal DC.
- These JMML-derived DCs exhibited high dextran endocytosis and stimulated allogeneic T cell proliferation in MLR.
- CD40L-matured JMML-derived DCs showed increased co-stimulatory molecules and chemotaxis but produced low IL-12 and high IL-10, leading to defective Th1 polarization and an immune-suppressive profile.
Conclusions:
- MNC from JMML patients spontaneously differentiate into DC with characteristics resembling normal DC.
- The cytokine profile of JMML-derived APCs is skewed towards immune suppression rather than eliciting a protective immune response.
- This aberrant immune response may contribute to the pathogenesis of JMML.