Receptors for immunoglobulin and complement on sheep RBC-binding lymphocytes in newborn infants

Sheep erythrocyte-binding human peripheral blood lymphocytes bearing receptors for the Fc-part of IgG and/or complement were studied in twenty newborn pre-term and term infants and fifteen adult controls. A technique with mixed rosettes and fluorescein-labelled sheep erythrocytes was used. The newborn infants had a significantly lower proportion of lymphocytes with receptors for sheep erythrocytes and the Fc-part of IgG (1.6%) than the adults (6.7%). Also the percentage of lymphocytes binding both sheep erythrocytes and complement-coated indicator cells was significantly lower in the newborn infants (2.6%) than in the adults (8.9%). A significantly higher proportion of lymphocytes had receptors for sheep erythrocytes and complement than for sheep erythrocytes and the Fc-part of IgG in both newborn infants and adults. There was no correlation between the values of lymphocytes binding sheep erythrocytes, or the Fc of IgG or complement and the proportion of mixed rosettes.