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.
Highlights
Activation, proliferation and differentiation of B lymphocytes are all controlled by signals delivered through receptors on the cell surface
We have previously identified a soluble factor released by mouse spleen cells activated in a mixed lymphocyte reaction (MLR), which could augment the expression of class I MHC antigens on tumor cell lines
Three hundred μl of proliferation inducing factor (PIF) preparation (900 μg protein) obtained after ammonium sulfate precipitation and a pH 2.0 dialysis of MLC supernatant were fractionated on a PP200SW HPLC column and the fractions were examined for PIF activity (25%, v/v) on mouse spleen cells as described in ‘Materials and Methods’
Summary
Activation, proliferation and differentiation of B lymphocytes are all controlled by signals delivered through receptors on the cell surface. These signals include antigen, interaction with molecules on the surface of other cell types, and a host of growth and differentiation inducing cytokines. Many of these cytokines are derived from T cells and are involved in T cell-B cell collaboration, but some are made by B cells, monocytes and a variety of non-lymphoid cells. We have attempted to characterize this proliferation inducing factor (PIF) This novel PIF released by activated mouse spleen cells appears to be distinct from MHC-AF as cell fractionation studies indicate that it induces proliferation in resting B cells
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