Eur J Immunol  1990 Aug;20(8):1767-73 

Ontogenic characterization of thymic B lymphocytes. Analysis in different mouse
strains.

Andreu-Sanchez JL, Faro J, Alonso JM, Paige CJ, Martinez C, Marcos MA.

Centro de Biologia Molecular, Universidad Autonoma, Madrid, Spain.

We have characterized a population of murine B lymphocytes present in the thymus
(TBL). They are a minor subset (0.2%-1% of total thymocytes), present from
perinatal periods onwards and constituted by activated cells with a high
proportion of Ig-secreting cells. They represent the first B lymphocytes
detected that secrete IgG after birth. Functional analysis reveals that the
frequency of lipopolysaccharide-responding cells in TBL is 5- to 10-fold lower
than in the spleen. TBL from adult mice did not show any significant difference
in their VH repertoire expression when compared to peripheral B lymphocytes.
Furthermore, we have been able to isolate a subpopulation of B220+IgM-CD3-
thymocytes whose putative B cell precursor potential needs to be directly
analyzed. These and other findings support the intrathymic resident
characteristics of TBL and suggest new ways of elucidating its physiological
role in the complex selective processes occurring inside the thymus.