Functional properties of human germinal center B cells.
Germinal centers (GCs) are histologically defined areas where B cells undergo extensive proliferation and maturation, or die of apoptosis. GC B cells isolated from human tonsils can be phenotypically identified by expression of peanut agglutinin (PNA)-binding sites and can be further divided into subpopulations based on their expression of CD77. To assess the functional potential of GC B cells, we studied CD77+ PNA+ B cells isolated from tonsils by examining their differentiation status and their ability to proliferate in vitro to various cytokines and costimulants. We found that CD77+ GC B cells are less differentiated than CD77- GC B cells; GC B cells less frequently express cytoplasmic IgG and IgM, and spontaneously secrete less Ig compared to CD77- GC B cells. To identify conditions capable of inducing GC B cell proliferation, we examined IL-4, IL-2, IFN-gamma, low molecular weight BCGF (LMW-BCGF), and an MLR supernatant along with costimulants such as anti-IgM antibody, Staphylococcus aureus Cowan I (SAC), PMA, and pokeweed mitogen (PWM). While non-GC B cells proliferate strongly in response to these stimuli, GC B cells did not proliferate. However, CD77+ as well as CD77- GC B cells mounted a rapid and strong proliferative response upon stimulation with IL-4, but only in the presence of anti-CD40 antibody. Moreover, although nine additional cytokines were examined, only IL-4 was capable of supporting CD77+ GC B cell proliferation in the presence of anti-CD40 antibody. When cells were stimulated with IL-4 and anti-CD40 antibody, we also found that IFN-gamma consistently decreased the proliferative response of CD77+ GC B cells without affecting the response of non-GC B cells. Taken together, these data indicate that GC B cells have characteristic growth requirements and that IL-4 may be important for GC B cell growth in vivo.
Butch
A W
AW
Department of Pathology, Washington University School of Medicine, St. Louis, Missouri 63110.
Nahm
M H
MH
D015703:Antigens, CD / Q000032:analysis; D010367:Arachis; D001402:B-Lymphocytes / Q000276:immunology*; D016207:Cytokines / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D015847:Interleukin-4 / Q000276:immunology; D037102:Lectins / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology*; D014066:Palatine Tonsil / Q000276:immunology*; D019887:Peanut Agglutinin; D037121:Plant Lectins; D014281:Trihexosylceramides / Q000032:analysis
D015703:Antigens, CD; D016207:Cytokines; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D037102:Lectins; D019887:Peanut Agglutinin; D037121:Plant Lectins; D014281:Trihexosylceramides; D015847:Interleukin-4; C018549:globotriaosylceramide