Phenotypic and functional characteristics of human newborns' B lymphocytes.
It has been demonstrated two major facts concerning human newborns' B lymphocytes: 1) they differentiate poorly into Ig-producing cells and 2) they express CD5 and CD1c membrane proteins. We have further analyzed human newborns' B cell characteristics and found that approximately half of them express activation Ag, i.e., 4F2 and IL-2R, both associated in significant proportions with CD23 and Bac-1. These membrane Ag were found both on CD5(+) and CD5(-) B cells. Newborns' B cells do not exhibit other activation markers because they express surface IgD, and because their size, RNA, and DNA contents do not differ from those of adults' B cells, indicating that they are in the G0/G1 cell cycle phase. Newborns' B cell proliferation can be induced by rIL-2, rIL-4, low m.w. B cell growth factor, and by Staphylococcus aureus protein A. It is presently difficult to build a hypothesis accounting for all the specific findings made on newborns' B cells. It is not known for instance whether CD5(+) and (-) B cells belong to distinct subsets as suggested by the fluorescence intensity curve obtained with an anti-CD5 antibody or to distinct stages in a unique pattern of B cell maturation during fetal and newborn life. This may indicate that partially activated B cells actually produce natural polyspecific autoantibodies of the IgM isotype found in newborns' human serum.
INSERM U 132, Hôpital des Enfants Malades, Paris, France.
A
A
Durandy
L
L
Thuillier
M
M
Forveille
A
A
Fischer
D015703:Antigens, CD / Q000032:analysis; D000943:Antigens, Differentiation / Q000032:analysis; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000502:physiology*; D018956:CD5 Antigens; D002454:Cell Differentiation; D002462:Cell Membrane / Q000276:immunology; D005434:Flow Cytometry; D006801:Humans; D007072:Immunoglobulin D / Q000032:analysis; D007231:Infant, Newborn / Q000276:immunology*; D007376:Interleukin-2 / Q000494:pharmacology; D015847:Interleukin-4 / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D011947:Receptors, Antigen, B-Cell / Q000032:analysis
D015703:Antigens, CD; D000943:Antigens, Differentiation; D018956:CD5 Antigens; D007072:Immunoglobulin D; D007376:Interleukin-2; D011947:Receptors, Antigen, B-Cell; D015847:Interleukin-4