B lymphocyte development in fetal liver. I. Development of reactivities to B cell mitogens "in vivo" and "in vitro"

Melchers, F.

European Journal of Immunology 7(7): 476-481


ISSN/ISBN: 0014-2980
PMID: 330170
DOI: 10.1002/eji.1830070714
Accession: 068526403

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Single cell suspensions of fetal M-secreting, IgA-secreting and IgG-secreting plaque-forming cells (PFC). The development of these PFC responses is mitogen-dependent: in the absence of LPS only 2-5% of the LPS-stimulated PFC responses developed. Only the magnitude, but not the development in time, of LPS reactivity of fetal liver cells was different in vivo and in vitro. This may indicate either that an early precursor cell to LPS-reactive B cells can only divide in vivo but not in vitro, or that early precursors continue to migrate with time of gestation into fetal liver. After birth B cells in liver were immediately reactive to LPS; however, they rapidly left the liver. Few, if any, dextrans sulfate or lipoprotein-reactive B cells, yielding a PFC response developed in fetal liver cells either in vivo or in vitro. Neonatal spleen contained immediately mitogen-reactive B cells. Comparable numbers of LPS, dextran sulfate and lipoprotein-reactive cells were found. Development of fetal liver cells to Ig-secreting PFC, occurred in 2 stages. The 1st .fwdarw. was independent of externally added mitogen (such as LPS), the 2nd .fwdarw. required the addition of mitogen. The majority of spleen cells had already passed this 1st stage of development.