The influence of thymosin on affinity binding in the E-rosette assay

Human peripheral blood lymphocytes (PBL) were analyzed in the E rosette assay with respect to (1) the effect of SRBC/lymphocyte ratio on rosette number; (2) the effect of this ratio on the presence of lymphocytes with multiple binding sites for SRBC; and (3) the influence of thymosin on increasing the number of lymphocyte receptors for SRBC. An increase in the SRBC/lymphocyte ratio was associated with an increase in rosette number. The number of multiple binding rosettes was also dependent on the SRBC/lymphocyte ratio. At saturing SRBC concentrations, greater than 30% of the rosettes were in the morula form. Treatment of PBL with thymosin was associated with a slight increase in the number of total rosettes and a large increase in number of morulas. It is suggested that the morula represents a mature form of T cell in contrast to the 2 - 3 SRBC rosette, which may be induced by thymosin to become a morula form.