IL7 binds HGF(495-728) to form PPBSF

The pre-pro-B cell growth-stimulating factor (PPBSF) is a self-assembling complex of Interleukin-7 (IL7 or IL-7) and a variant beta-chain of hepatocyte growth factor (HGFbeta) (Lai & Goldschneider 2001). This 55 kDa heterodimer, unlike monomeric IL7, selectively stimulates proliferation and differentiation of pre-pro-B cells in a long-term bone marrow culture system and up-regulates Interleukin-7 receptor alpha chain (IL7R) expression on pre-pro-B cell surface. It has been postulated that PPBSF is the active form of IL7 that normally induces IL7R-low pre-pro-B cells to proliferate and differentiate into IL7R-high pro-B cells, which then proliferate and differentiate into pre-B-cells on stimulation with monomeric IL7 (Wei et al. 2002).

预增殖B细胞生长刺激因子（PPBSF）是由白介素-7（IL7或IL-7）及其变异的肝细胞生长因子β链（HGFbeta）组成的自组装复合体（Lai & Goldschneider 2001）。此55 kDa的异源二聚体，与单体IL7不同，能够在长期骨髓培养系统中选择性促进预增殖B细胞的增殖与分化，并上调预增殖B细胞表面的白介素-7受体α链（IL7R）的表达。据此推测，PPBSF可能是通常诱导IL7R低表达预增殖B细胞增殖并分化为IL7R高表达前B细胞的IL7的活性形式，随后这些前B细胞在单体IL7的刺激下进一步增殖和分化为B细胞（Wei et al. 2002）。