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Effects of normal mouse serum on the IL-3-induced proliferation of bone marrow cells
1Department of Immunology, Karolinska Institute, Stockholm, Sweden.
Abstract:
Normal mouse serum (NMS) devoid of colony-stimulating factor (CSF) was found to enhance the interleukin 3 (IL-3)-driven colony formation of bone marrow in vitro. Inclusion of NMS in bone marrow colony-forming assays resulted in greatly increased numbers of colonies and clusters following seven days incubation; however, incubation of bone marrow with NMS before the colony-forming assay had no effect on resultant colony number. The levels of serum-enhancing activity (SEA) did not appear to vary significantly with age and in part was species restricted, in that human and guinea pig serum did not enhance mouse bone marrow colony formation. Conversely, NMS had no effect on human bone marrow colony formation. Levels of SEA were found to vary between strains, as did the degree to which bone marrow from various strains was enhanced by the serum. Serum fractionation studies indicated three active fractions with molecular weights of 800-900 Kd, 60-70 Kd, and 20-30 Kd. The fraction at 800-900 Kd inhibited colony formation at high concentrations and enhanced colony formation on dilution, whereas the two other active fractions contained enhancing activity at all concentrations tested. These results would indicate that normal serum can play a greater role in colony-forming assays than nutritional supplements. The relationship of the SEA factors to other factors that have been reported to modulate bone marrow colony formation is discussed.
Insights
Normal mouse serum enhances bone marrow colony formation in vitro by providing serum-enhancing activity (SEA). This effect is specific and involves multiple molecular weight fractions, suggesting serum
Area of Science:
- Hematology
- Immunology
- Cell Biology
Background:
- Colony-stimulating factors (CSFs) are known regulators of hematopoiesis.
- The role of normal serum in modulating bone marrow colony formation in vitro is not fully understood.
- Interleukin-3 (IL-3) is a key cytokine driving myeloid progenitor proliferation.
Purpose of the Study:
- To investigate the effect of normal mouse serum (NMS) on interleukin-3 (IL-3)-driven bone marrow colony formation.
- To characterize the nature and properties of serum-enhancing activity (SEA).
Main Methods:
- Bone marrow colony-forming assays were performed in the presence of NMS.
- NMS was incubated with bone marrow cells before or during the assay.
- Serum fractionation was performed using molecular weight cut-off filters.
- Species specificity and strain variations in SEA were assessed.
Main Results:
- NMS significantly increased the number of bone marrow colonies and clusters in IL-3-driven assays.
- Pre-incubation of bone marrow with NMS did not affect colony numbers.
- Serum-enhancing activity (SEA) was species-restricted (mouse serum enhanced mouse marrow, not human or guinea pig).
- SEA levels varied between mouse strains and their bone marrow responsiveness.
- Fractionation identified three active serum components with molecular weights of 800-900 Kd, 60-70 Kd, and 20-30 Kd.
Conclusions:
- Normal mouse serum contains factors that significantly enhance IL-3-driven bone marrow colony formation in vitro.
- This enhancing activity is mediated by specific molecular weight fractions and is not due to pre-incubation effects.
- Normal serum plays a more substantial role in colony-forming assays than previously recognized, independent of nutritional supplementation.