Identification of albumin as the serum factor essential for the growth of activated human lymphocytes.
Albumin from human, bovine, or rabbit serum supported the growth of concanavalin A-stimulated human thymus-derived lymphocytes equally well. This activity was completely abolished by pepsin digestion. It was shown for bovine serum albumin that the albumin molecule itself, and neither an impurity nor a factor bound to albumin was essential for the growth of lymphocytes. This conclusion was based on observations that the growth-promoting activity could not be removed from albumin, and that the specific activity of albumin remained unaltered after the following procedures: molecular sieving at pH 7.5 at pH 3.0, and in 8 M urea at pH 6.6; ion exchange chromatography at pH 4.3 and in 8 M urea at pH 7.2; isoelectric focusing; charcoal treatment; acetone precipitation; and reduction with 2-mercaptoethanol in the presence of 8 M urea. Dimeric albumin was found to support growth of lymphocytes as well as monomeric albumin, and mercaptalbumin and non-mercaptalbumin were shown to have equal activity.
Identification of albumin as the serum factor essential for the growth of activated human lymphocytes. Albumin from human, bovine, or rabbit serum supported the growth of concanavalin A-stimulated human thymus-derived lymphocytes equally well. This activity was completely abolished by pepsin digestion. It was shown for bovine serum albumin that the albumin molecule itself, and neither an impurity nor a factor bound to albumin was essential for the growth of lymphocytes. This conclusion was based on observations that the growth-promoting activity could not be removed from albumin, and that the specific activity of albumin remained unaltered after the following procedures: molecular sieving at pH 7.5 at pH 3.0, and in 8 M urea at pH 6.6; ion exchange chromatography at pH 4.3 and in 8 M urea at pH 7.2; isoelectric focusing; charcoal treatment; acetone precipitation; and reduction with 2-mercaptoethanol in the presence of 8 M urea. Dimeric albumin was found to support growth of lymphocytes as well as monomeric albumin, and mercaptalbumin and non-mercaptalbumin were shown to have equal activity.