Human pre-B cells differentiate into Ig-secreting plasma cells in the presence of interleukin-4 and activated CD4+ T cells or their membranes.
Studies on human B-cell development have been hampered by the lack of reproducible culture techniques to induce pre-B cells to differentiate into Ig-secreting plasma cells. Here, we describe that highly purified surface (s) mu-, cytoplasmic (c) mu+, CD10+, CD19+ human pre-B cells derived from fetal bone marrow (BM) differentiate with high frequencies into Ig-secreting plasma cells, when cocultured with activated, cloned CD4+ T cells and with interleukin-4 (IL-4). Production of IgM, total IgG, IgG4, and IgE in pre-B-cell cultures was detected, indicating that the cells also underwent Ig isotype switching. Pre-B-cell differentiation occurred in the absence of BM stromal cells, IL-7, and stem cell factor (SCF). However, IL-7 significantly enhanced the levels of Ig produced, whereas SCF was ineffective. Neutralizing anti-IL-4 monoclonal antibodies (MoAbs) completely inhibited pre-B-cell differentiation showing the specificity of the reaction. Intact CD4+ T-cell clones could be replaced by membrane preparations of these cells, indicating that the costimulatory signals provided by the activated CD4+ T cells are contact-mediated. In contrast, anti-CD40 MoAbs failed to provide the costimulatory signal required for pre-B-cell differentiation, which may be related to the very low expression of CD40 on fetal BM B cells. Activated CD4+ T cells and IL-4 also induced s mu expression and Ig synthesis in cultures initiated with pre-B cells that had been preincubated in medium for 2 days, and from which spontaneously emerging s mu+ B cells were removed by using a fluorescence-activated cell sorter. These results support the notion that the Ig synthesis observed in pre-B-cell cultures was not caused by outgrowth and differentiation of cells that spontaneously matured into s mu+ B cells. In addition, IL-4 and CD4+ T cells strongly enhanced CD40 and HLA-DR expression on the majority of cultured pre-B cells, further indicating that CD4+ T cells and IL-4 activate bona fide pre-B cells. Taken together, these data indicate that activated CD4+ T cells and IL-4 can provide all the necessary signals required for human pre-B cells to differentiate into Ig-secreting plasma cells.
Punnonen
J
J
DNAX Research Institute of Molecular and Cellular Biology, Human Immunology Department, Palo Alto, CA 94304-1104.
Aversa
G
G
de Vries
J E
JE
D015703:Antigens, CD / Q000032:analysis; D001402:B-Lymphocytes / Q000502:physiology*; D001483:Base Sequence; D001853:Bone Marrow / Q000276:immunology; D001854:Bone Marrow Cells; D015496:CD4-Positive T-Lymphocytes / Q000502:physiology*; D002454:Cell Differentiation; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D005260:Female; D016298:Hematopoietic Cell Growth Factors / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D006801:Humans; D007136:Immunoglobulins / Q000096:biosynthesis*; D015847:Interleukin-4 / Q000494:pharmacology*; D015851:Interleukin-7 / Q000494:pharmacology; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D010950:Plasma Cells / Q000276:immunology / Q000502:physiology*; D011247:Pregnancy; D019089:Stem Cell Factor
D015703:Antigens, CD; D016298:Hematopoietic Cell Growth Factors; D007136:Immunoglobulins; D015851:Interleukin-7; D019089:Stem Cell Factor; D015847:Interleukin-4