Lymphocyte activation. VIII. The application of a whole blood test to the quantitative analysis of PHA responsive T cells.

In diluted blood predominantly T cells responded to purified PHA (pure leucoagglutinin Wellcome). Red cells and non-T mononuclear cells increased PHA responsiveness of T cells at concentrations present in the peripheral blood. Addition of polymorphonuclear leucocytes was a very slight further advantage. The incorporation of [3H] thymidine reflected the numbers of T cells in culture, although not perfectly linearly, since counts increased when more T cells were added to the cultures. It was therefore concluded that in cultures of diluted whole blood non-specific amplification mechanisms were provided and responses reflected the performance of stimulated T lymphocytes. Since the method is simple and the number of technical variables is relatively small, it is possible to establish a "normal" range of PHA responsiveness expressed in absolute counts per minute, and thus directly compare results from different laboratories.