Cytokine expression by germinal center cells.
Germinal centers (GC) primarily consist of B cells along with a small number of T cells (5 to 10%) and follicular dendritic cells (FDC) (< or = 1%). Although extensive Ag-driven B cell proliferation and maturation occurs in GC, very little is known about the role of cytokines in the development of GC B cells. Therefore, to identify cytokines present in the GC microenvironment that may influence B cell development, we systematically examined cytokine gene expression by GC cells. GC T cells (CD57+/CD4+), GC B cells (CD77+), and FDC (HJ2+) were isolated from human tonsils by cell sorting using a flow cytometer. Freshly isolated GC cells were examined for mRNA expression for IL-1 alpha, IL-1 beta, IL-2, IL-3, IL-4, IL-5, IL-6, IL-10, TNF-alpha, and IFN-gamma using reverse transcription polymerase chain reaction. Freshly isolated GC T cells consistently expressed IL-4 mRNA (11 of 12 tonsils), whereas CD57- Th cells (mostly non-GC Th cells) were often negative for IL-4 mRNA. When the other nine cytokine mRNA were studied, freshly isolated CD57+ Th cells occasionally expressed mRNA for IL-10, TNF-alpha, and IFN-gamma. CD57- Th cells were occasionally positive for IL-1 beta, IL-10, IFN-gamma, and TNF-alpha, and negative for IL-2 and IL-6. Freshly isolated GC B cells as well as FDC failed to express detectable quantities of mRNA for all 10 cytokines that were studied. Thus, IL-4 is the only cytokine out of 10 that is consistently expressed in GC and may be important for the development of B cells in GC. After stimulation of CD57+ Th cells with PWM, production of IL-4 mRNA was dramatically reduced, whereas CD57- Th cell production of IL-4 was greatly augmented. This finding indicates that GC T cells may differ from other Th cells in cytokine gene expression and that results of cytokine production obtained after in vitro stimulation do not always reflect in vivo results.
Butch
A W
AW
Department of Pathology, Washington University School of Medicine, St. Louis, MO 63110.
Chung
G H
GH
Hoffmann
J W
JW
Nahm
M H
MH
D015703:Antigens, CD / Q000032:analysis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D001402:B-Lymphocytes / Q000378:metabolism; D001483:Base Sequence; D018959:CD57 Antigens; D016207:Cytokines / Q000235:genetics*; D003713:Dendritic Cells / Q000378:metabolism; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis / Q000235:genetics; D015847:Interleukin-4 / Q000096:biosynthesis / Q000235:genetics; D008969:Molecular Sequence Data; D014066:Palatine Tonsil / Q000166:cytology* / Q000276:immunology / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D006377:T-Lymphocytes, Helper-Inducer / Q000378:metabolism; D014158:Transcription, Genetic
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D018959:CD57 Antigens; D016207:Cytokines; D007376:Interleukin-2; D012333:RNA, Messenger; D015847:Interleukin-4