Immuno-architecture of human fetal lymphoid tissues

Spleen, thymus and lymph node of human fetuses from the 12th to the 38rd week (spleen from 9 weeks) were investigated in an immunohistological study on B5-fixed paraffin embedded tissues, employing a panel of recently developed monoclonal antibodies, reactive with antigens resistant against fixation and paraffin embedment. The monoclonal antibodies included were MT1, MT2, MB1, MB2, MB3, LN1, LN2, LN3, LeuM1, Leu7, VIE-G4, together with polyclonal antibodies reactive with immunoglobulin heavy and light chains, and with lysozyme and S100-protein. The preservation of morphological detail together with immunoperoxidase staining of cellular subsets, allowed an accurate determination of the ontogenic development of the different cell types in situ, in relation to their micro-environment. The use of paraffin tissue reactive (monoclonal) antibodies gives an extra dimension to the study of fetal lymphoid tissues. This is of particular advantage in studies on very fragile tissues as in early embryonal and fetal ontogeny.