RESUMO
The morphology and distribution of pre-B cells and the changes of antigens during the differentiation from pre-B to B cells in fetal livers of different gestational ages were studied by means of immunohistochemical technique. The results revealed that at earlyfetal stage(between 9 and 29 weeks), the liver contained numerous pre-B cells, which were different in shapes and sizes, but their phenotypic expression was identical, for instance, 1gM, BA-1, HLA-DR and TdT all appeared positive. Most of pre-B cells were scattered in perisinusoidal space, only a few of them were present in sinusoids or around the blood vessels. After the 13the week, 1gD and 1gA positive cells began to appear, and the number of OKB-2 and Leul4 positive cells was markedly increased subsquently. Meanwhile, the number of the HLA-DR, Kappa and Lambda positive cells was increased accordingly, which indicated that the B cells became more mature. In view of absence of antigenic stimulation, the B cells failed to develop into plasma cells. Moreover, it was observed that the differentiation and maturation of the B cells in the fetal liver seemed to be independent on the T cells, because the B cells continued to generate even if the T cells were absent at early stage of fetal liver. It showed that the differentiation and the development of the B cells in the fetuses were mainly dependent on the liver microenvironment. This study provided an evidence for treatment of aplastic anemia and agammaglobulinemia with fetal liver between 9 and 20 weeks old.
