Lymphocyte markers in the bovine foetus

The ontogeny of lymphocyte surface markers was studied in thymus, retropharyngeal lymph nodes, spleen, bone marrow, and liver of 48 bovine foetuses, 80-280 days of gestation. The markers examined were the spontaneous (E) rosette against sheep erythrocytes (SRBCs) in foetal calf serum (E/FCS), in medium supplemented with gelatin (E/CFG), and in medium supplemented with dextran (E/dextran), the erythrocyte-antibody (EA) rosette for immunoglobulin (Fc) receptors, the erythrocyte-antibody-complement (EAC) rosette for complement receptors, and the immunofluorescence test (IFT) for surface-membrane immunoglobulins (SmIg). E-rosette-forming cells (RFCs) occurred in the thymus in substantial numbers throughout the period studied, in spleen and lymph nodes only after 160 days, and in bone marrow and liver rarely. The dynamics of E rosettes formed in the three supplements suggested that each supplement might be supporting rosette formation by different populations of cells, albeit considerable overlap might be expected. Organ distribution and development of EA and EAC RFCs did not parallel the expected ontogeny of any class of lymphocytes. Cells carrying SmIg developed mainly in spleen and lymph nodes. Towards the end of gestation some cells in liver also had SmIg.