Two-dimensional Polyacrylamide gel electrophoresis has been used to display about 400 of the major proteins of human peripheral blood lymphocytes in PHA-treated and untreated cultures pulse labeled with radioactive amino acids. Although protein synthetic rates increase 10-fold and protein concentrations 5-fold with mitogen treatment, no qualitative change is seen in the population of proteins visualized. However, specific reproducible alterations in the relative synthetic rates of certain proteins are noted. Four hours after addition of PHA, total protein synthesis is 50% increased over control, but only a few proteins show a disproportionate increase in synthetic rate. Synthesis of a 25,000 m.w., pl 5.2 protein is most prominently enhanced at 4 hr. After 24 hr of PHA, a 60,000 m.w., pl 6.1 protein and a 50,000 m.w., pl 5.6 protein are prominently stimulated by PHA above the generalized increase in synthetic rate of all visualized proteins. The alterations seen after 48 and 120 hr of PHA stimulation are very similar to those after 24 hr. Coomassie Blue staining of these gels confirms a relative and absolute increase in the total quantity of these proteins. Con A and pokeweed mitogen produce virtually identical changes. Two lymphoblastoid cell lines (MOLT-4 and NAMALVA) also show high growth rates and high proportions of these proteins. Computer-assisted densitometry and statistical analysis of the changes in relative synthetic rates of 24 of the major cellular proteins confirm the visual impressions from the fluorographs. Thus, this study has shown that a number of quantitative, but no qualitative, changes arise in the major cellular proteins in association with growth activation of lymphocytes by a mitogen. If induction of new proteins or repression of synthesis of any resting-cell proteins occurs, it must involve proteins present in small numbers, which are below the limits of resolution of the methods used.
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Lester et al. (1981) studied this question.