Background: In previous studies, we developed several monoclonal antib
odies (mAbs) against fetal and adult rat liver to analyze the hemopoie
tic microenvironment of the fetal liver during the gestational period.
In this study, we hat-e developed two new mAbs against fetal rat live
r cells and have examined the characteristics at various gestational a
ges of fetal liver and of adult liver. Methods: The characteristics of
these monoclonal antibodies were demonstrated by examining several ti
ssues using immunohistochemical staining and flow cytofluorometry. Res
ults: Monoclonal antibodies HAM10 and HAM11 were developed against fet
al rat liver cells. These reacted with the cytoplasm of fetal and adul
t hepatocytes. HAM10 antigen expression was strong at approximately da
y 18 of gestation in the active period of hemopoiesis in fetal rat liv
er but was much lower in adult liver. HAM10 antigen expression also in
creased in liver after partial hepatectomy and was reduced abruptly to
a normal level thereafter. HAM11 antigen expression in fetal liver wa
s weaker than that of HAM10 antigen expression. The degree of HAM11 an
tigen expression increased as gestation proceeded, reaching a maximum
in adult liver. Conclusions: Both HAM10 and HAM11 antigens may play a
role in the morphogenesis of hepatocytes and in the hemopoietic microe
nvironment for hemopoietic cells. Moreover, HAM10 antigen is may play
a role in hepatocyte proliferation in the fetal liver, whereas HAM11 a
ntigen may contribute to the maturation of fetal- to the adult-type he
patocytes. (C) 1996 Wiley-Liss, Inc.