Distribution of actin content in human B and T lymphocytes by DNAse 1 inhibition test

The DNAse inhibition assay, which allows for the titration of two forms of soluble actin in cell extracts, has been applied to normal human lymphocytes from peripheral blood. Actin-like activities associated with the membrane-rich fraction of extracts from thymus dependent (T) lymphocytes are significantly higher than those from bone marrow derived (B) lymphocytes, on a per cell basis, provided care is paid to the elimination of monocytic and polymorphonuclear cells which produce significantly higher DNAse 1 inhibition. The apparent discrepancy with a recent report that normal T and B lymphocytes do not differ in their total actin content is discussed with respect to the functional uniqueness of membrane-associated DNAse 1 inhibitions and the importance of using purified lymphocyte populations.