Comparative activation requirements of human peripheral blood, spleen, and lymph node B cells

Human peripheral blood, spleen, and lymph node B cells were stimulated with Cowan I Staphylococcus aureus (SA) or F(ab')₂ fragments of anti-μ antibody (anti-μ) and various lymphokines and were analyzed for proliferation and generation of Ig-secreting cells (ISC). SA alone but not anti-μ stimulated minimal proliferation of each population. Recombinant IL 2 (r-IL 2) effectively promoted proliferation of SA-stimulated blood and spleen B cells, but supported less vigorous responses of lymph node B cells. By contrast, r-IL 2 enhanced DNA synthesis of all anti-μ-stimulated B cells early in culture, but did not promote sustained proliferation of anti-μ-stimulated lymph node B cells and only promoted ongoing DNA synthesis of some anti-μ-activated blood (eight out of 17) and spleen (five out of 14) B cell preparations. Recombinant interferon-γ (r-IFN-γ) and a commercial preparation of B cell growth factor (BCGF) also augmented DNA synthesis of all three B cell populations stimulated with SA or anti-μ early in culture, but neither alone was able to sustain maximal proliferation. Markedly enhanced sustained proliferation of all three anti-μ- and SA-stimulated B cell populations was noted when cultures were supported by the combination of r-IL 2 and BCGF, or to a lesser extent by r-IL 2 and r-IFN-γ. The generation of ISC from SA-stimulated blood or spleen but not lymph node B cells was effectively supported by r-IL 2 alone. Differentiation of lymph node B cells required the combination of r-IL 2 and BCGF. These studies emphasize the importance of both the activation stimulus and the origin of the B cells in determining the lymphokine requirements of human B cell responsiveness.