Rosette formation with sheep erythrocytes--a possible T-cell marker in the pig.

A proportion of pig lymphocytes form rosettes with sheep erythrocytes. Factors affecting their demonstration have been investigated, and a standard technique defined. Rosette-forming lymphocytes lacked surface immunoglobulin detected by immunofluorescence and formation of rosettes was not inhibited by anti-immunoglobulin or anti-PLA sera, but was by anti-thymus serum. Of 18 species' erythrocytes tested only sheep, Barbary sheep and Mouflon erythrocytes formed rosettes in similar percentages. Fetal sheep erythrocytes formed no rosettes at 6o days of gestation and developed adult levels by term. Rosettes were formed by the majority of thymus cells, by only few bone marrow cells and by intermediate proportions of cells in other lymphoid tissues correlating with the probable order of T cell content. In pig fetuses, thymus contained postnatal levels of rosette-forming cells by 69 days, when such cells were not detected in other tissues. These data support the contention that SRBC rosettes are formed by T lymphocytes.