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Development of human connective tissue mast cells from purified blood monocytes
Abstract:
Highly purified subfractions of human peripheral blood monocytes, when cultured in the presence of 30% L cell supernatant and 30% horse serum, assumed all the characteristics that define human connective tissue mast cells. After three weeks of culture, 75% of the cells developed metachromasia and granular chloroacetate esterase staining, and their intracellular histamine levels increased from 0.0 to 50.5 ng/10(6) cells. On electron microscopy, the cells developed intracytoplasmic granules with all the features typical for mature and immature mast cells. Cultured cells bound 55 pg 125I-IgE/10(6) cells, while labelling was negligible with cells prior to culture and with heat-denatured 125I-IgE. Fluorescent staining with anti-IgE increased slightly as well, while staining with monoclonal anti-monocyte and anti-HLA-Dr markers decreased. Purified lymphocytes did not assume mast cell characteristics, and lymphokines did not induce or enhance in vitro mast cell development or IgE binding. The data therefore further support the concept that connective tissue mast cells arise from the monocytoid lineage.
Insights
Human monocytes can transform into connective tissue mast cells in vitro. This study demonstrates monocytes acquire mast cell characteristics, including histamine content and IgE binding, supporting their monocytoid lineage origin.
Area of Science:
- Immunology
- Cell Biology
- Hematology
Background:
- Connective tissue mast cells (CTMCs) are crucial immune cells involved in allergic responses.
- The developmental origin of CTMCs has been a subject of ongoing research and debate.
Purpose of the Study:
- To investigate whether human peripheral blood monocytes can differentiate into CTMCs in vitro.
- To characterize the phenotypic and functional changes of monocytes during this differentiation process.
Main Methods:
- Highly purified human peripheral blood monocytes were cultured with L cell supernatant and horse serum.
- Cells were analyzed after three weeks for metachromasia, chloroacetate esterase staining, intracellular histamine levels, and electron microscopy.
- Immunoglobulin E (IgE) binding capacity and surface marker expression (anti-IgE, anti-monocyte, anti-HLA-Dr) were assessed using fluorescent staining.
Main Results:
- Cultured monocytes exhibited key mast cell characteristics, including metachromasia, positive chloroacetate esterase staining, and significantly increased intracellular histamine levels.
- Electron microscopy revealed intracytoplasmic granules typical of mature and immature mast cells.
- Differentiated cells demonstrated specific binding of 125I-IgE, while pre-culture cells and lymphocytes did not.
- Monocyte and HLA-Dr marker expression decreased, while anti-IgE staining slightly increased.
Conclusions:
- Human monocytes can differentiate into cells with the defining characteristics of connective tissue mast cells under specific culture conditions.
- These findings provide further evidence supporting the monocytoid lineage as the origin of connective tissue mast cells.
- Lymphokines do not appear to play a role in inducing or enhancing this in vitro mast cell development.