Purification to homogeneity of B cell stimulating factor. A molecule that stimulates proliferation of multiple lymphokine-dependent cell lines.

Abstract

The differentiation of resting B lymphocytes to Ig secretion involves several sequential steps regulated by antigen, T lymphocytes, and macrophages. The requirement for T cells may in some cases be replaced by lymphokines secreted upon T cell activation (1, 2). A number of distinct T cell-derived lymphokines have been described (3-9) that directly regulate the growth and maturation of B cells. These include IL-2 (3, 4), (5,6), and at least two additional, yet less well-characterized molecules, B cell stimulating factor, (also known as B cell growth factor, BCGF or BSF-1) ~ (7, 8), and B cell differentiation factor (BCGF-II or BCDF) (9). BSF-1 was originally (7) described as a factor that stimulated proliferation of B cells in conjunction with a submitogenic concentration of antiIg. Recent studies (10, 1 1) have shown that semipurified BSF-1 acts on resting B cells, facilitating their entry into S phase upon subsequent interaction with anti-Ig. These studies (1 1) indicate that BSF-1 might actually be a differentiation factor, and they further suggest that BSF-1 may not have growth factor activity.We have purified BSF-1 to homogeneity from culture supernatants of mitogenactivated EL4 thymoma cells. We used the proliferation of highly purified splenic B cells in the presence ofanti-IgM as an assay in our purification procedure. The purification was also monitored for additional lymphokines using the factordependent cell lines CTLL-2 and FDC-P2. Interestingly, fractions containing BSF-1 always contained stimulatory activity for both IL-2-and IL-3-dependent cell lines, even though these fractions were devoid of IL-2 and IL-3 protein. Nterminal amino acid sequencing of homogeneous BSF-1 revealed a unique protein sequence completely different from that of murine IL-2 or IL-3. Based on these results, we conclude that BSF-1 is both a growth and differentiation factor that may have biologic effects beyond the B lymphocyte compartment. Materials and MethodsMice. Female C57BL/6J mice were obtained from The Jackson Laboratory, Bar Harbor, ME, and were used at 8-12 wk of age.Abbreviations used in this paper: BSF-1, B cell-stimulating factor; DIEA-Ac, N,N-diisopropylethylamine; TFA, trifluoroacetic acid; TMS-silica, trimethylsilyl-silica.J. Exe. MED.

Three-Dimensional Solution Structure of Human Interleukin-4 by Multidimensional Heteronuclear Magnetic Resonance Spectroscopy

“…4 and is made up of Lys 6 , Glu 13 , Lys 16 In addition, sequence alignments between the human and mouse IL-4 sequences result in a gap in the mouse sequence relative to the human one either at the beginning (28) or end of helix α C (29), and therefore probably constitutes the region with the largest conformational differences between the human and mouse protein. This difference may account for the observation that human and mouse IL-4 do not exhibit cross-species activity with regard to either receptor binding or biological function (30,31). 8.…”

Role of T Cells in Atopic Dermatitis

“…A breakthrough in understanding the potential role of T cells in AD was the discovery of the T-cell-derived cytokine interleukin (IL)-4 [14, 15]. Its main activity is the (co)promotion of IgE synthesis [16, 17].…”

Heterogeneity of helper/inducer T lymphocytes. II. Effects of interleukin 4- and interleukin 2-producing T cell clones on resting B lymphocytes.

“…The activity of this preparation was determined at Immunex Corp. uudexpressed inunits as defined (19). Murine and human rIL-2 were purchased from Genzyme Corp ., Boston, MA, and used according to units as defined by the supplier.…”