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Published on: March 6, 2010
Induction of proliferation in resting B-cells by a factor released by activated mouse spleen cells
1School of Life Sciences Jawaharlal Nehru University, New Delhi, India.
Insights
A novel soluble factor, proliferation inducing factor (PIF), stimulates mouse spleen cell proliferation. This heat-stable, 25 kDa factor specifically activates B cells, independent of lipopolysaccharide (LPS) pathways.
Area of Science:
- Immunology
- Cell Biology
Background:
- Mixed lymphocyte reactions (MLRs) generate soluble factors that modulate immune cell activity.
- Understanding these factors is crucial for dissecting immune responses and developing immunotherapies.
Purpose of the Study:
- To characterize a novel proliferation-inducing factor (PIF) released during MLRs.
- To identify the specific cell type responsible for proliferation in response to PIF.
Main Methods:
- Spleen cells were activated in an MLR to collect supernatant containing PIF.
- PIF's stability was tested via heat and enzymatic treatments.
- Molecular weight was estimated using size exclusion HPLC.
- Cell proliferation assays were performed on T cell-depleted and B cell-depleted spleen cells.
Main Results:
- PIF is heat-stable (90°C for 45 min) and resistant to trypsin/chymotrypsin.
- PIF has an estimated molecular weight of 25 kDa.
- B cell-depleted spleen cells did not proliferate in response to PIF, indicating B cells are the target.
- PIF-induced proliferation was not inhibited by Polymixin-B, differentiating it from LPS responses.
Conclusions:
- A novel 25 kDa, heat-stable soluble factor (PIF) induces B cell proliferation.
- PIF represents a distinct pathway for B cell activation, separate from LPS-mediated signaling.
Abstract:
Mouse spleen cells activated in a mixed lymphocyte reaction release a soluble factor, which induces a significant proliferative response in fresh mouse spleen cells. This proliferation inducing factor (PIF) was found to be heat stable (90 degrees C for 45 min) and also resistant to trypsin or chymotrypsin treatment. By using a sizing HPLC column, the molecular weight of PIF appears to be 25 kDa. Mouse spleen cells treated with anti-thy-1 + complement lost Con-A induced proliferative responses but responded well to PIF. B cell depleted spleen cells obtained by negative selection panning, did not respond to PIF. These results indicate that B cells proliferated in response to PIF. Polymixin-B, which blocks the B cell proliferative response to LPS, did not inhibit PIF induced proliferation.
