Early biochemical changes in phytohemagglutinin-stimulated peripheral blood lymphocytes from normal and tumor-bearing rats

The very early increase in the intracellular concentration of 3′,5′-cyclic GMP and in the rate of incorporation of ³³P into membrane phospholipid, and the early increases in the level of uridine kinase and cystathionine synthetase upon stimulation of peripheral lymphocytes with phytohemagglutinin, correlate well with the standard assay for lymphoblastic transformation. The rapidity, lower variability and in particular greater sensitivity of assays based on earlier events, suggests that they may be useful adjuncts for assessing immunocompetence under specified conditions, and in combination, may aid in diagnosing the molecular lesion when immunity is impaired. Coincidentally this study also shows that the peripheral blood lymphocytes from animals bearing transplantable tumors are inherently incompetent, and also that the serum from such animals suppresses the transformation of lymphocytes from normal animals. The immunosuppressive effect of the transplantable tumors was independent of the adrenal cortex.