Interleukin 7（IL-7）is a mature protein of 177 amino acids with a signal sequence of 25 amino
acids and a calculated mass of 17.4kDa. Recombinant human IL-7 stimulated the
proliferation of murine pre-B cells and was active on cells harvested from
human bone marrow that are enriched for B-lineage progenitor cells.

IL-7 is a proteinaceous biological response modifier that has a bioactive
tertiary structure dependent on disulfide bond formation.

IL-7-stimulated pro-B cells partially differentiated into a pre-B cell
population, on the basis of the loss of CD34 and terminal deoxynucleotidyl
（TdT） expression, and the acquisition of cytoplasmic mu heavy chains.