Bovine lymphocytes: recognition of cells forming spontaneous (E) rosettes

About 20% of thymus lymphocytes from neonatal calves formed spontaneous (E) rosettes with SRBCs in medium consisting of 50-100% foetal calf serum (FCS); other media were less satisfactory. FCS was necessary both to allow rosette formation to occur and to maintain stability of the rosettes once formed. Rosettes were stable at 0 degrees C but unstable at 18 degrees C and 37 degrees C. Dead thymus cell (sodium azide treated) did not form rosettes. Treatment of thymus cells with antiserum to bovine Ig-inhibited rosette formation, but this inhibition was considered non-specific since it also occurred with normal rabbit serum. Treatment of SRBCs with neuraminidase slightly enhanced rosette formation by thymus cells, but did not induce peripheral blood lymphocytes to form rosettes. Rosette formation did not occur under a variety of conditions with normal or neuraminidase-treated human, horse, pig, rabbit, guinea-pig, chicken or autologous RBCs. SRBC rosette forming cells were also found in lymph nodes (2-14%) and spleen (less than 5%), but rarely or never in peripheral blood and bone marrow of calves and adults. In foetuses at 80 days of gestation, 49% of thymus cells formed E rosettes. Foetal lymph node cells formed E rosettes at 160 days and spleen at 180 days. Cells with membrane-bound Ig were observed by IFT; their distribution did not coincide with the occurrence of E rosettes. E-rosette formation might be a marker for a subpopulation of bovine T cells.